Merge branch 'expand-stack'

This modifies our user mode stack expansion code to always take the
mmap_lock for writing before modifying the VM layout.

It's actually something we always technically should have done, but
because we didn't strictly need it, we were being lazy ("opportunistic"
sounds so much better, doesn't it?) about things, and had this hack in
place where we would extend the stack vma in-place without doing the
proper locking.

And it worked fine.  We just needed to change vm_start (or, in the case
of grow-up stacks, vm_end) and together with some special ad-hoc locking
using the anon_vma lock and the mm->page_table_lock, it all was fairly
straightforward.

That is, it was all fine until Ruihan Li pointed out that now that the
vma layout uses the maple tree code, we *really* don't just change
vm_start and vm_end any more, and the locking really is broken.  Oops.

It's not actually all _that_ horrible to fix this once and for all, and
do proper locking, but it's a bit painful.  We have basically three
different cases of stack expansion, and they all work just a bit
differently:

 - the common and obvious case is the page fault handling. It's actually
   fairly simple and straightforward, except for the fact that we have
   something like 24 different versions of it, and you end up in a maze
   of twisty little passages, all alike.

 - the simplest case is the execve() code that creates a new stack.
   There are no real locking concerns because it's all in a private new
   VM that hasn't been exposed to anybody, but lockdep still can end up
   unhappy if you get it wrong.

 - and finally, we have GUP and page pinning, which shouldn't really be
   expanding the stack in the first place, but in addition to execve()
   we also use it for ptrace(). And debuggers do want to possibly access
   memory under the stack pointer and thus need to be able to expand the
   stack as a special case.

None of these cases are exactly complicated, but the page fault case in
particular is just repeated slightly differently many many times.  And
ia64 in particular has a fairly complicated situation where you can have
both a regular grow-down stack _and_ a special grow-up stack for the
register backing store.

So to make this slightly more manageable, the bulk of this series is to
first create a helper function for the most common page fault case, and
convert all the straightforward architectures to it.

Thus the new 'lock_mm_and_find_vma()' helper function, which ends up
being used by x86, arm, powerpc, mips, riscv, alpha, arc, csky, hexagon,
loongarch, nios2, sh, sparc32, and xtensa.  So we not only convert more
than half the architectures, we now have more shared code and avoid some
of those twisty little passages.

And largely due to this common helper function, the full diffstat of
this series ends up deleting more lines than it adds.

That still leaves eight architectures (ia64, m68k, microblaze, openrisc,
parisc, s390, sparc64 and um) that end up doing 'expand_stack()'
manually because they are doing something slightly different from the
normal pattern.  Along with the couple of special cases in execve() and
GUP.

So there's a couple of patches that first create 'locked' helper
versions of the stack expansion functions, so that there's a obvious
path forward in the conversion.  The execve() case is then actually
pretty simple, and is a nice cleanup from our old "grow-up stackls are
special, because at execve time even they grow down".

The #ifdef CONFIG_STACK_GROWSUP in that code just goes away, because
it's just more straightforward to write out the stack expansion there
manually, instead od having get_user_pages_remote() do it for us in some
situations but not others and have to worry about locking rules for GUP.

And the final step is then to just convert the remaining odd cases to a
new world order where 'expand_stack()' is called with the mmap_lock held
for reading, but where it might drop it and upgrade it to a write, only
to return with it held for reading (in the success case) or with it
completely dropped (in the failure case).

In the process, we remove all the stack expansion from GUP (where
dropping the lock wouldn't be ok without special rules anyway), and add
it in manually to __access_remote_vm() for ptrace().

Thanks to Adrian Glaubitz and Frank Scheiner who tested the ia64 cases.
Everything else here felt pretty straightforward, but the ia64 rules for
stack expansion are really quite odd and very different from everything
else.  Also thanks to Vegard Nossum who caught me getting one of those
odd conditions entirely the wrong way around.

Anyway, I think I want to actually move all the stack expansion code to
a whole new file of its own, rather than have it split up between
mm/mmap.c and mm/memory.c, but since this will have to be backported to
the initial maple tree vma introduction anyway, I tried to keep the
patches _fairly_ minimal.

Also, while I don't think it's valid to expand the stack from GUP, the
final patch in here is a "warn if some crazy GUP user wants to try to
expand the stack" patch.  That one will be reverted before the final
release, but it's left to catch any odd cases during the merge window
and release candidates.

Reported-by: Ruihan Li <lrh2000@pku.edu.cn>

* branch 'expand-stack':
  gup: add warning if some caller would seem to want stack expansion
  mm: always expand the stack with the mmap write lock held
  execve: expand new process stack manually ahead of time
  mm: make find_extend_vma() fail if write lock not held
  powerpc/mm: convert coprocessor fault to lock_mm_and_find_vma()
  mm/fault: convert remaining simple cases to lock_mm_and_find_vma()
  arm/mm: Convert to using lock_mm_and_find_vma()
  riscv/mm: Convert to using lock_mm_and_find_vma()
  mips/mm: Convert to using lock_mm_and_find_vma()
  powerpc/mm: Convert to using lock_mm_and_find_vma()
  arm64/mm: Convert to using lock_mm_and_find_vma()
  mm: make the page fault mmap locking killable
  mm: introduce new 'lock_mm_and_find_vma()' page fault helper

49 files changed, 439 insertions, 468 deletions

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index a5c2b1aa46b0..d6968d090d49 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -30,6 +30,7 @@ config ALPHA
 	select HAS_IOPORT
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_MOD_ARCH_SPECIFIC
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select ODD_RT_SIGACTION
 	select OLD_SIGSUSPEND
diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c
index 7b01ae4f3bc6..8c9850437e67 100644
--- a/arch/alpha/mm/fault.c
+++ b/arch/alpha/mm/fault.c
@@ -119,20 +119,12 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
 		flags |= FAULT_FLAG_USER;
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
-		goto bad_area;
+		goto bad_area_nosemaphore;
 
 	/* Ok, we have a good vm_area for this memory access, so
 	   we can handle it.  */
- good_area:
 	si_code = SEGV_ACCERR;
 	if (cause < 0) {
 		if (!(vma->vm_flags & VM_EXEC))
@@ -192,6 +184,7 @@ retry:
  bad_area:
 	mmap_read_unlock(mm);
 
+ bad_area_nosemaphore:
 	if (user_mode(regs))
 		goto do_sigsegv;
 
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index ab6d701365bb..96cf8720bb93 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -41,6 +41,7 @@ config ARC
 	select HAVE_PERF_EVENTS
 	select HAVE_SYSCALL_TRACEPOINTS
 	select IRQ_DOMAIN
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select OF
 	select OF_EARLY_FLATTREE
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index 5ca59a482632..f59e722d147f 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -113,15 +113,9 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
-	mmap_read_lock(mm);
-
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (unlikely(address < vma->vm_start)) {
-		if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
-			goto bad_area;
-	}
+		goto bad_area_nosemaphore;
 
 	/*
 	 * vm_area is good, now check permissions for this memory access
@@ -161,6 +155,7 @@ retry:
 bad_area:
 	mmap_read_unlock(mm);
 
+bad_area_nosemaphore:
 	/*
 	 * Major/minor page fault accounting
 	 * (in case of retry we only land here once)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index cef741bb03b3..d60b73d93e03 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -127,6 +127,7 @@ config ARM
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
 	select IRQ_FORCED_THREADING
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_REL
 	select NEED_DMA_MAP_STATE
 	select OF_EARLY_FLATTREE if OF
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 83598649a094..fef62e4a9edd 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -235,37 +235,11 @@ static inline bool is_permission_fault(unsigned int fsr)
 	return false;
 }
 
-static vm_fault_t __kprobes
-__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int flags,
-		unsigned long vma_flags, struct pt_regs *regs)
-{
-	struct vm_area_struct *vma = find_vma(mm, addr);
-	if (unlikely(!vma))
-		return VM_FAULT_BADMAP;
-
-	if (unlikely(vma->vm_start > addr)) {
-		if (!(vma->vm_flags & VM_GROWSDOWN))
-			return VM_FAULT_BADMAP;
-		if (addr < FIRST_USER_ADDRESS)
-			return VM_FAULT_BADMAP;
-		if (expand_stack(vma, addr))
-			return VM_FAULT_BADMAP;
-	}
-
-	/*
-	 * ok, we have a good vm_area for this memory access, check the
-	 * permissions on the VMA allow for the fault which occurred.
-	 */
-	if (!(vma->vm_flags & vma_flags))
-		return VM_FAULT_BADACCESS;
-
-	return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
-}
-
 static int __kprobes
 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
 	int sig, code;
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
@@ -304,31 +278,21 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 
-	/*
-	 * As per x86, we may deadlock here.  However, since the kernel only
-	 * validly references user space from well defined areas of the code,
-	 * we can bug out early if this is from code which shouldn't.
-	 */
-	if (!mmap_read_trylock(mm)) {
-		if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
-			goto no_context;
 retry:
-		mmap_read_lock(mm);
-	} else {
-		/*
-		 * The above down_read_trylock() might have succeeded in
-		 * which case, we'll have missed the might_sleep() from
-		 * down_read()
-		 */
-		might_sleep();
-#ifdef CONFIG_DEBUG_VM
-		if (!user_mode(regs) &&
-		    !search_exception_tables(regs->ARM_pc))
-			goto no_context;
-#endif
+	vma = lock_mm_and_find_vma(mm, addr, regs);
+	if (unlikely(!vma)) {
+		fault = VM_FAULT_BADMAP;
+		goto bad_area;
 	}
 
-	fault = __do_page_fault(mm, addr, flags, vm_flags, regs);
+	/*
+	 * ok, we have a good vm_area for this memory access, check the
+	 * permissions on the VMA allow for the fault which occurred.
+	 */
+	if (!(vma->vm_flags & vm_flags))
+		fault = VM_FAULT_BADACCESS;
+	else
+		fault = handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
 
 	/* If we need to retry but a fatal signal is pending, handle the
 	 * signal first. We do not need to release the mmap_lock because
@@ -359,6 +323,7 @@ retry:
 	if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
 		return 0;
 
+bad_area:
 	/*
 	 * If we are in kernel mode at this point, we
 	 * have no context to handle this fault with.
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3ae5c03ded0e..595028bd9160 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -231,6 +231,7 @@ config ARM64
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
 	select KASAN_VMALLOC if KASAN
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select NEED_DMA_MAP_STATE
 	select NEED_SG_DMA_LENGTH
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c60100791bcc..935f0a8911f9 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -497,27 +497,14 @@ static void do_bad_area(unsigned long far, unsigned long esr,
 #define VM_FAULT_BADMAP		((__force vm_fault_t)0x010000)
 #define VM_FAULT_BADACCESS	((__force vm_fault_t)0x020000)
 
-static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr,
+static vm_fault_t __do_page_fault(struct mm_struct *mm,
+				  struct vm_area_struct *vma, unsigned long addr,
 				  unsigned int mm_flags, unsigned long vm_flags,
 				  struct pt_regs *regs)
 {
-	struct vm_area_struct *vma = find_vma(mm, addr);
-
-	if (unlikely(!vma))
-		return VM_FAULT_BADMAP;
-
 	/*
 	 * Ok, we have a good vm_area for this memory access, so we can handle
 	 * it.
-	 */
-	if (unlikely(vma->vm_start > addr)) {
-		if (!(vma->vm_flags & VM_GROWSDOWN))
-			return VM_FAULT_BADMAP;
-		if (expand_stack(vma, addr))
-			return VM_FAULT_BADMAP;
-	}
-
-	/*
 	 * Check that the permissions on the VMA allow for the fault which
 	 * occurred.
 	 */
@@ -631,31 +618,15 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 	}
 lock_mmap:
 #endif /* CONFIG_PER_VMA_LOCK */
-	/*
-	 * As per x86, we may deadlock here. However, since the kernel only
-	 * validly references user space from well defined areas of the code,
-	 * we can bug out early if this is from code which shouldn't.
-	 */
-	if (!mmap_read_trylock(mm)) {
-		if (!user_mode(regs) && !search_exception_tables(regs->pc))
-			goto no_context;
+
 retry:
-		mmap_read_lock(mm);
-	} else {
-		/*
-		 * The above mmap_read_trylock() might have succeeded in which
-		 * case, we'll have missed the might_sleep() from down_read().
-		 */
-		might_sleep();
-#ifdef CONFIG_DEBUG_VM
-		if (!user_mode(regs) && !search_exception_tables(regs->pc)) {
-			mmap_read_unlock(mm);
-			goto no_context;
-		}
-#endif
+	vma = lock_mm_and_find_vma(mm, addr, regs);
+	if (unlikely(!vma)) {
+		fault = VM_FAULT_BADMAP;
+		goto done;
 	}
 
-	fault = __do_page_fault(mm, addr, mm_flags, vm_flags, regs);
+	fault = __do_page_fault(mm, vma, addr, mm_flags, vm_flags, regs);
 
 	/* Quick path to respond to signals */
 	if (fault_signal_pending(fault, regs)) {
@@ -674,9 +645,7 @@ retry:
 	}
 	mmap_read_unlock(mm);
 
-#ifdef CONFIG_PER_VMA_LOCK
 done:
-#endif
 	/*
 	 * Handle the "normal" (no error) case first.
 	 */
diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 95f1e9bfd1c7..cf2a6fd7dff8 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -97,6 +97,7 @@ config CSKY
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
+	select LOCK_MM_AND_FIND_VMA
 	select MAY_HAVE_SPARSE_IRQ
 	select MODULES_USE_ELF_RELA if MODULES
 	select OF
diff --git a/arch/csky/mm/fault.c b/arch/csky/mm/fault.c
index e15f736cca4b..ae9781b7d92e 100644
--- a/arch/csky/mm/fault.c
+++ b/arch/csky/mm/fault.c
@@ -97,13 +97,12 @@ static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_f
 	BUG();
 }
 
-static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
+static inline void bad_area_nosemaphore(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
 {
 	/*
 	 * Something tried to access memory that isn't in our memory map.
 	 * Fix it, but check if it's kernel or user first.
 	 */
-	mmap_read_unlock(mm);
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs)) {
 		do_trap(regs, SIGSEGV, code, addr);
@@ -238,20 +237,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 	if (is_write(regs))
 		flags |= FAULT_FLAG_WRITE;
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, addr);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (unlikely(!vma)) {
-		bad_area(regs, mm, code, addr);
-		return;
-	}
-	if (likely(vma->vm_start <= addr))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
-		bad_area(regs, mm, code, addr);
-		return;
-	}
-	if (unlikely(expand_stack(vma, addr))) {
-		bad_area(regs, mm, code, addr);
+		bad_area_nosemaphore(regs, mm, code, addr);
 		return;
 	}
 
@@ -259,11 +247,11 @@ retry:
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it.
 	 */
-good_area:
 	code = SEGV_ACCERR;
 
 	if (unlikely(access_error(regs, vma))) {
-		bad_area(regs, mm, code, addr);
+		mmap_read_unlock(mm);
+		bad_area_nosemaphore(regs, mm, code, addr);
 		return;
 	}
 
diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index 54eadf265178..6726f4941015 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -28,6 +28,7 @@ config HEXAGON
 	select GENERIC_SMP_IDLE_THREAD
 	select STACKTRACE_SUPPORT
 	select GENERIC_CLOCKEVENTS_BROADCAST
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select GENERIC_CPU_DEVICES
 	select ARCH_WANT_LD_ORPHAN_WARN
diff --git a/arch/hexagon/mm/vm_fault.c b/arch/hexagon/mm/vm_fault.c
index 4b578d02fd01..7295ea3f8cc8 100644
--- a/arch/hexagon/mm/vm_fault.c
+++ b/arch/hexagon/mm/vm_fault.c
@@ -57,21 +57,10 @@ void do_page_fault(unsigned long address, long cause, struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
-	if (!vma)
-		goto bad_area;
+	vma = lock_mm_and_find_vma(mm, address, regs);
+	if (unlikely(!vma))
+		goto bad_area_nosemaphore;
 
-	if (vma->vm_start <= address)
-		goto good_area;
-
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-
-	if (expand_stack(vma, address))
-		goto bad_area;
-
-good_area:
 	/* Address space is OK.  Now check access rights. */
 	si_code = SEGV_ACCERR;
 
@@ -143,6 +132,7 @@ good_area:
 bad_area:
 	mmap_read_unlock(mm);
 
+bad_area_nosemaphore:
 	if (user_mode(regs)) {
 		force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 		return;
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 85c4d9ac8686..5458b52b4009 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -110,10 +110,12 @@ retry:
          * register backing store that needs to expand upwards, in
          * this case vma will be null, but prev_vma will ne non-null
          */
-        if (( !vma && prev_vma ) || (address < vma->vm_start) )
-		goto check_expansion;
+        if (( !vma && prev_vma ) || (address < vma->vm_start) ) {
+		vma = expand_stack(mm, address);
+		if (!vma)
+			goto bad_area_nosemaphore;
+	}
 
-  good_area:
 	code = SEGV_ACCERR;
 
 	/* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
@@ -177,35 +179,9 @@ retry:
 	mmap_read_unlock(mm);
 	return;
 
-  check_expansion:
-	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
-		if (!vma)
-			goto bad_area;
-		if (!(vma->vm_flags & VM_GROWSDOWN))
-			goto bad_area;
-		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
-		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
-			goto bad_area;
-		if (expand_stack(vma, address))
-			goto bad_area;
-	} else {
-		vma = prev_vma;
-		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
-		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
-			goto bad_area;
-		/*
-		 * Since the register backing store is accessed sequentially,
-		 * we disallow growing it by more than a page at a time.
-		 */
-		if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
-			goto bad_area;
-		if (expand_upwards(vma, address))
-			goto bad_area;
-	}
-	goto good_area;
-
   bad_area:
 	mmap_read_unlock(mm);
+  bad_area_nosemaphore:
 	if ((isr & IA64_ISR_SP)
 	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 	{
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index cbab4f9ca15c..32b9da4622ce 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -131,6 +131,7 @@ config LOONGARCH
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN if !SMP
 	select IRQ_FORCED_THREADING
 	select IRQ_LOONGARCH_CPU
+	select LOCK_MM_AND_FIND_VMA
 	select MMU_GATHER_MERGE_VMAS if MMU
 	select MODULES_USE_ELF_RELA if MODULES
 	select NEED_PER_CPU_EMBED_FIRST_CHUNK
diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index 449087bd589d..da5b6d518cdb 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -169,22 +169,18 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
-	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (!expand_stack(vma, address))
-		goto good_area;
+	vma = lock_mm_and_find_vma(mm, address, regs);
+	if (unlikely(!vma))
+		goto bad_area_nosemaphore;
+	goto good_area;
+
 /*
  * Something tried to access memory that isn't in our memory map..
  * Fix it, but check if it's kernel or user first..
  */
 bad_area:
 	mmap_read_unlock(mm);
+bad_area_nosemaphore:
 	do_sigsegv(regs, write, address, si_code);
 	return;
 
diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index 228128e45c67..c290c5c0cfb9 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -105,8 +105,9 @@ retry:
 		if (address + 256 < rdusp())
 			goto map_err;
 	}
-	if (expand_stack(vma, address))
-		goto map_err;
+	vma = expand_stack(mm, address);
+	if (!vma)
+		goto map_err_nosemaphore;
 
 /*
  * Ok, we have a good vm_area for this memory access, so
@@ -196,10 +197,12 @@ bus_err:
 	goto send_sig;
 
 map_err:
+	mmap_read_unlock(mm);
+map_err_nosemaphore:
 	current->thread.signo = SIGSEGV;
 	current->thread.code = SEGV_MAPERR;
 	current->thread.faddr = address;
-	goto send_sig;
+	return send_fault_sig(regs);
 
 acc_err:
 	current->thread.signo = SIGSEGV;
diff --git a/arch/microblaze/mm/fault.c b/arch/microblaze/mm/fault.c
index 687714db6f4d..d3c3c33b73a6 100644
--- a/arch/microblaze/mm/fault.c
+++ b/arch/microblaze/mm/fault.c
@@ -192,8 +192,9 @@ retry:
 			&& (kernel_mode(regs) || !store_updates_sp(regs)))
 				goto bad_area;
 	}
-	if (expand_stack(vma, address))
-		goto bad_area;
+	vma = expand_stack(mm, address);
+	if (!vma)
+		goto bad_area_nosemaphore;
 
 good_area:
 	code = SEGV_ACCERR;
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index ada18f3be229..d49d5fc40021 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -92,6 +92,7 @@ config MIPS
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN if 64BIT || !SMP
 	select IRQ_FORCED_THREADING
 	select ISA if EISA
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_REL if MODULES
 	select MODULES_USE_ELF_RELA if MODULES && 64BIT
 	select PERF_USE_VMALLOC
diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index a27045f5a556..d7878208bd3f 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -99,21 +99,13 @@ static void __do_page_fault(struct pt_regs *regs, unsigned long write,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
-		goto bad_area;
+		goto bad_area_nosemaphore;
 /*
  * Ok, we have a good vm_area for this memory access, so
  * we can handle it..
  */
-good_area:
 	si_code = SEGV_ACCERR;
 
 	if (write) {
diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig
index e5936417d3cd..d54464021a61 100644
--- a/arch/nios2/Kconfig
+++ b/arch/nios2/Kconfig
@@ -16,6 +16,7 @@ config NIOS2
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_KGDB
 	select IRQ_DOMAIN
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select OF
 	select OF_EARLY_FLATTREE
diff --git a/arch/nios2/mm/fault.c b/arch/nios2/mm/fault.c
index ca64eccea551..e3fa9c15181d 100644
--- a/arch/nios2/mm/fault.c
+++ b/arch/nios2/mm/fault.c
@@ -86,27 +86,14 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
-	if (!mmap_read_trylock(mm)) {
-		if (!user_mode(regs) && !search_exception_tables(regs->ea))
-			goto bad_area_nosemaphore;
 retry:
-		mmap_read_lock(mm);
-	}
-
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
-		goto bad_area;
+		goto bad_area_nosemaphore;
 /*
  * Ok, we have a good vm_area for this memory access, so
  * we can handle it..
  */
-good_area:
 	code = SEGV_ACCERR;
 
 	switch (cause) {
diff --git a/arch/openrisc/mm/fault.c b/arch/openrisc/mm/fault.c
index 6734fee3134f..a9dcd4381d1a 100644
--- a/arch/openrisc/mm/fault.c
+++ b/arch/openrisc/mm/fault.c
@@ -127,8 +127,9 @@ retry:
 		if (address + PAGE_SIZE < regs->sp)
 			goto bad_area;
 	}
-	if (expand_stack(vma, address))
-		goto bad_area;
+	vma = expand_stack(mm, address);
+	if (!vma)
+		goto bad_area_nosemaphore;
 
 	/*
 	 * Ok, we have a good vm_area for this memory access, so
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 6941fdbf2517..6e894afa4249 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -288,15 +288,19 @@ void do_page_fault(struct pt_regs *regs, unsigned long code,
 retry:
 	mmap_read_lock(mm);
 	vma = find_vma_prev(mm, address, &prev_vma);
-	if (!vma || address < vma->vm_start)
-		goto check_expansion;
+	if (!vma || address < vma->vm_start) {
+		if (!prev || !(prev->vm_flags & VM_GROWSUP))
+			goto bad_area;
+		vma = expand_stack(mm, address);
+		if (!vma)
+			goto bad_area_nosemaphore;
+	}
+
 /*
  * Ok, we have a good vm_area for this memory access. We still need to
  * check the access permissions.
  */
 
-good_area:
-
 	if ((vma->vm_flags & acc_type) != acc_type)
 		goto bad_area;
 
@@ -347,17 +351,13 @@ good_area:
 	mmap_read_unlock(mm);
 	return;
 
-check_expansion:
-	vma = prev_vma;
-	if (vma && (expand_stack(vma, address) == 0))
-		goto good_area;
-
 /*
  * Something tried to access memory that isn't in our memory map..
  */
 bad_area:
 	mmap_read_unlock(mm);
 
+bad_area_nosemaphore:
 	if (user_mode(regs)) {
 		int signo, si_code;
 
@@ -449,7 +449,7 @@ handle_nadtlb_fault(struct pt_regs *regs)
 {
 	unsigned long insn = regs->iir;
 	int breg, treg, xreg, val = 0;
-	struct vm_area_struct *vma, *prev_vma;
+	struct vm_area_struct *vma;
 	struct task_struct *tsk;
 	struct mm_struct *mm;
 	unsigned long address;
@@ -485,7 +485,7 @@ handle_nadtlb_fault(struct pt_regs *regs)
 				/* Search for VMA */
 				address = regs->ior;
 				mmap_read_lock(mm);
-				vma = find_vma_prev(mm, address, &prev_vma);
+				vma = vma_lookup(mm, address);
 				mmap_read_unlock(mm);
 
 				/*
@@ -494,7 +494,6 @@ handle_nadtlb_fault(struct pt_regs *regs)
 				 */
 				acc_type = (insn & 0x40) ? VM_WRITE : VM_READ;
 				if (vma
-				    && address >= vma->vm_start
 				    && (vma->vm_flags & acc_type) == acc_type)
 					val = 1;
 			}
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8eb6c5e9e4f8..395044b705a1 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -277,6 +277,7 @@ config PPC
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
 	select KASAN_VMALLOC			if KASAN && MODULES
+	select LOCK_MM_AND_FIND_VMA
 	select MMU_GATHER_PAGE_SIZE
 	select MMU_GATHER_RCU_TABLE_FREE
 	select MMU_GATHER_MERGE_VMAS
diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c
index 7c507fb48182..f49fd873df8d 100644
--- a/arch/powerpc/mm/copro_fault.c
+++ b/arch/powerpc/mm/copro_fault.c
@@ -33,19 +33,11 @@ int copro_handle_mm_fault(struct mm_struct *mm, unsigned long ea,
 	if (mm->pgd == NULL)
 		return -EFAULT;
 
-	mmap_read_lock(mm);
-	ret = -EFAULT;
-	vma = find_vma(mm, ea);
+	vma = lock_mm_and_find_vma(mm, ea, NULL);
 	if (!vma)
-		goto out_unlock;
-
-	if (ea < vma->vm_start) {
-		if (!(vma->vm_flags & VM_GROWSDOWN))
-			goto out_unlock;
-		if (expand_stack(vma, ea))
-			goto out_unlock;
-	}
+		return -EFAULT;
 
+	ret = -EFAULT;
 	is_write = dsisr & DSISR_ISSTORE;
 	if (is_write) {
 		if (!(vma->vm_flags & VM_WRITE))
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 531177a4ee08..5bfdf6ecfa96 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -84,11 +84,6 @@ static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
 	return __bad_area_nosemaphore(regs, address, si_code);
 }
 
-static noinline int bad_area(struct pt_regs *regs, unsigned long address)
-{
-	return __bad_area(regs, address, SEGV_MAPERR);
-}
-
 static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
 				    struct vm_area_struct *vma)
 {
@@ -515,40 +510,12 @@ lock_mmap:
 	 * we will deadlock attempting to validate the fault against the
 	 * address space.  Luckily the kernel only validly references user
 	 * space from well defined areas of code, which are listed in the
-	 * exceptions table.
-	 *
-	 * As the vast majority of faults will be valid we will only perform
-	 * the source reference check when there is a possibility of a deadlock.
-	 * Attempt to lock the address space, if we cannot we then validate the
-	 * source.  If this is invalid we can skip the address space check,
-	 * thus avoiding the deadlock.
+	 * exceptions table. lock_mm_and_find_vma() handles that logic.
 	 */
-	if (unlikely(!mmap_read_trylock(mm))) {
-		if (!is_user && !search_exception_tables(regs->nip))
-			return bad_area_nosemaphore(regs, address);
-
 retry:
-		mmap_read_lock(mm);
-	} else {
-		/*
-		 * The above down_read_trylock() might have succeeded in
-		 * which case we'll have missed the might_sleep() from
-		 * down_read():
-		 */
-		might_sleep();
-	}
-
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (unlikely(!vma))
-		return bad_area(regs, address);
-
-	if (unlikely(vma->vm_start > address)) {
-		if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
-			return bad_area(regs, address);
-
-		if (unlikely(expand_stack(vma, address)))
-			return bad_area(regs, address);
-	}
+		return bad_area_nosemaphore(regs, address);
 
 	if (unlikely(access_pkey_error(is_write, is_exec,
 				       (error_code & DSISR_KEYFAULT), vma)))
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c69572fbe613..a08917f681af 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -127,6 +127,7 @@ config RISCV
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
 	select KASAN_VMALLOC if KASAN
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA if MODULES
 	select MODULE_SECTIONS if MODULES
 	select OF
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 8685f85a7474..35a84ec69a9f 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -84,13 +84,13 @@ static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_f
 	BUG();
 }
 
-static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
+static inline void
+bad_area_nosemaphore(struct pt_regs *regs, int code, unsigned long addr)
 {
 	/*
 	 * Something tried to access memory that isn't in our memory map.
 	 * Fix it, but check if it's kernel or user first.
 	 */
-	mmap_read_unlock(mm);
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs)) {
 		do_trap(regs, SIGSEGV, code, addr);
@@ -100,6 +100,15 @@ static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code
 	no_context(regs, addr);
 }
 
+static inline void
+bad_area(struct pt_regs *regs, struct mm_struct *mm, int code,
+	 unsigned long addr)
+{
+	mmap_read_unlock(mm);
+
+	bad_area_nosemaphore(regs, code, addr);
+}
+
 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
 {
 	pgd_t *pgd, *pgd_k;
@@ -287,23 +296,10 @@ void handle_page_fault(struct pt_regs *regs)
 	else if (cause == EXC_INST_PAGE_FAULT)
 		flags |= FAULT_FLAG_INSTRUCTION;
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, addr);
+	vma = lock_mm_and_find_vma(mm, addr, regs);
 	if (unlikely(!vma)) {
 		tsk->thread.bad_cause = cause;
-		bad_area(regs, mm, code, addr);
-		return;
-	}
-	if (likely(vma->vm_start <= addr))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
-		tsk->thread.bad_cause = cause;
-		bad_area(regs, mm, code, addr);
-		return;
-	}
-	if (unlikely(expand_stack(vma, addr))) {
-		tsk->thread.bad_cause = cause;
-		bad_area(regs, mm, code, addr);
+		bad_area_nosemaphore(regs, code, addr);
 		return;
 	}
 
@@ -311,7 +307,6 @@ retry:
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it.
 	 */
-good_area:
 	code = SEGV_ACCERR;
 
 	if (unlikely(access_error(cause, vma))) {
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index b65144c392b0..dbe8394234e2 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -457,8 +457,9 @@ retry:
 	if (unlikely(vma->vm_start > address)) {
 		if (!(vma->vm_flags & VM_GROWSDOWN))
 			goto out_up;
-		if (expand_stack(vma, address))
-			goto out_up;
+		vma = expand_stack(mm, address);
+		if (!vma)
+			goto out;
 	}
 
 	/*
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index e339745f62a1..2b3ce4fd3956 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -60,6 +60,7 @@ config SUPERH
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select IRQ_FORCED_THREADING
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select NEED_SG_DMA_LENGTH
 	select NO_DMA if !MMU && !DMA_COHERENT
diff --git a/arch/sh/mm/fault.c b/arch/sh/mm/fault.c
index acd2f5e50bfc..06e6b4952924 100644
--- a/arch/sh/mm/fault.c
+++ b/arch/sh/mm/fault.c
@@ -439,21 +439,9 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 	}
 
 retry:
-	mmap_read_lock(mm);
-
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (unlikely(!vma)) {
-		bad_area(regs, error_code, address);
-		return;
-	}
-	if (likely(vma->vm_start <= address))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
-		bad_area(regs, error_code, address);
-		return;
-	}
-	if (unlikely(expand_stack(vma, address))) {
-		bad_area(regs, error_code, address);
+		bad_area_nosemaphore(regs, error_code, address);
 		return;
 	}
 
@@ -461,7 +449,6 @@ retry:
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
 	 */
-good_area:
 	if (unlikely(access_error(error_code, vma))) {
 		bad_area_access_error(regs, error_code, address);
 		return;
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 6197b87f2b3b..49849790e66d 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -58,6 +58,7 @@ config SPARC32
 	select DMA_DIRECT_REMAP
 	select GENERIC_ATOMIC64
 	select HAVE_UID16
+	select LOCK_MM_AND_FIND_VMA
 	select OLD_SIGACTION
 	select ZONE_DMA
 
diff --git a/arch/sparc/mm/fault_32.c b/arch/sparc/mm/fault_32.c
index 179295b14664..a3ccc0267bc2 100644
--- a/arch/sparc/mm/fault_32.c
+++ b/arch/sparc/mm/fault_32.c
@@ -143,28 +143,19 @@ asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
 	if (pagefault_disabled() || !mm)
 		goto no_context;
 
+	if (!from_user && address >= PAGE_OFFSET)
+		goto no_context;
+
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
 retry:
-	mmap_read_lock(mm);
-
-	if (!from_user && address >= PAGE_OFFSET)
-		goto bad_area;
-
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
-		goto bad_area;
+		goto bad_area_nosemaphore;
 	/*
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
 	 */
-good_area:
 	code = SEGV_ACCERR;
 	if (write) {
 		if (!(vma->vm_flags & VM_WRITE))
@@ -321,17 +312,9 @@ static void force_user_fault(unsigned long address, int write)
 
 	code = SEGV_MAPERR;
 
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
-		goto bad_area;
-good_area:
+		goto bad_area_nosemaphore;
 	code = SEGV_ACCERR;
 	if (write) {
 		if (!(vma->vm_flags & VM_WRITE))
@@ -350,6 +333,7 @@ good_area:
 	return;
 bad_area:
 	mmap_read_unlock(mm);
+bad_area_nosemaphore:
 	__do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
 	return;
 
diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
index d8a407fbe350..e326caf708c6 100644
--- a/arch/sparc/mm/fault_64.c
+++ b/arch/sparc/mm/fault_64.c
@@ -386,8 +386,9 @@ continue_fault:
 				goto bad_area;
 		}
 	}
-	if (expand_stack(vma, address))
-		goto bad_area;
+	vma = expand_stack(mm, address);
+	if (!vma)
+		goto bad_area_nosemaphore;
 	/*
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
@@ -490,8 +491,9 @@ exit_exception:
 	 * Fix it, but check if it's kernel or user first..
 	 */
 bad_area:
-	insn = get_fault_insn(regs, insn);
 	mmap_read_unlock(mm);
+bad_area_nosemaphore:
+	insn = get_fault_insn(regs, insn);
 
 handle_kernel_fault:
 	do_kernel_fault(regs, si_code, fault_code, insn, address);
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index d3ce21c4ca32..6d8ae86ae978 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -47,14 +47,15 @@ retry:
 	vma = find_vma(mm, address);
 	if (!vma)
 		goto out;
-	else if (vma->vm_start <= address)
+	if (vma->vm_start <= address)
 		goto good_area;
-	else if (!(vma->vm_flags & VM_GROWSDOWN))
+	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto out;
-	else if (is_user && !ARCH_IS_STACKGROW(address))
-		goto out;
-	else if (expand_stack(vma, address))
+	if (is_user && !ARCH_IS_STACKGROW(address))
 		goto out;
+	vma = expand_stack(mm, address);
+	if (!vma)
+		goto out_nosemaphore;
 
 good_area:
 	*code_out = SEGV_ACCERR;
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d5c69145a73c..b3ebf58cf77e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -279,6 +279,7 @@ config X86
 	select HOTPLUG_SMT			if SMP
 	select HOTPLUG_SPLIT_STARTUP		if SMP && X86_32
 	select IRQ_FORCED_THREADING
+	select LOCK_MM_AND_FIND_VMA
 	select NEED_PER_CPU_EMBED_FIRST_CHUNK
 	select NEED_PER_CPU_PAGE_FIRST_CHUNK
 	select NEED_SG_DMA_LENGTH
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e4399983c50c..e8711b2cafaf 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -880,12 +880,6 @@ __bad_area(struct pt_regs *regs, unsigned long error_code,
 	__bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
 }
 
-static noinline void
-bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
-{
-	__bad_area(regs, error_code, address, 0, SEGV_MAPERR);
-}
-
 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
 		struct vm_area_struct *vma)
 {
@@ -1366,51 +1360,10 @@ void do_user_addr_fault(struct pt_regs *regs,
 lock_mmap:
 #endif /* CONFIG_PER_VMA_LOCK */
 
-	/*
-	 * Kernel-mode access to the user address space should only occur
-	 * on well-defined single instructions listed in the exception
-	 * tables.  But, an erroneous kernel fault occurring outside one of
-	 * those areas which also holds mmap_lock might deadlock attempting
-	 * to validate the fault against the address space.
-	 *
-	 * Only do the expensive exception table search when we might be at
-	 * risk of a deadlock.  This happens if we
-	 * 1. Failed to acquire mmap_lock, and
-	 * 2. The access did not originate in userspace.
-	 */
-	if (unlikely(!mmap_read_trylock(mm))) {
-		if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
-			/*
-			 * Fault from code in kernel from
-			 * which we do not expect faults.
-			 */
-			bad_area_nosemaphore(regs, error_code, address);
-			return;
-		}
 retry:
-		mmap_read_lock(mm);
-	} else {
-		/*
-		 * The above down_read_trylock() might have succeeded in
-		 * which case we'll have missed the might_sleep() from
-		 * down_read():
-		 */
-		might_sleep();
-	}
-
-	vma = find_vma(mm, address);
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (unlikely(!vma)) {
-		bad_area(regs, error_code, address);
-		return;
-	}
-	if (likely(vma->vm_start <= address))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
-		bad_area(regs, error_code, address);
-		return;
-	}
-	if (unlikely(expand_stack(vma, address))) {
-		bad_area(regs, error_code, address);
+		bad_area_nosemaphore(regs, error_code, address);
 		return;
 	}
 
@@ -1418,7 +1371,6 @@ retry:
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
 	 */
-good_area:
 	if (unlikely(access_error(error_code, vma))) {
 		bad_area_access_error(regs, error_code, address, vma);
 		return;
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index c1bcfc2a8581..2a51a466779f 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -49,6 +49,7 @@ config XTENSA
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select IRQ_DOMAIN
+	select LOCK_MM_AND_FIND_VMA
 	select MODULES_USE_ELF_RELA
 	select PERF_USE_VMALLOC
 	select TRACE_IRQFLAGS_SUPPORT
diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
index faf7cf35a0ee..d1eb8d6c5b82 100644
--- a/arch/xtensa/mm/fault.c
+++ b/arch/xtensa/mm/fault.c
@@ -130,23 +130,14 @@ void do_page_fault(struct pt_regs *regs)
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
-
+	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (!vma)
-		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
-		goto bad_area;
+		goto bad_area_nosemaphore;
 
 	/* Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
 	 */
 
-good_area:
 	code = SEGV_ACCERR;
 
 	if (is_write) {
@@ -205,6 +196,7 @@ good_area:
 	 */
 bad_area:
 	mmap_read_unlock(mm);
+bad_area_nosemaphore:
 	if (user_mode(regs)) {
 		force_sig_fault(SIGSEGV, code, (void *) address);
 		return;
diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
index 864e4ffb6aa9..261352a23271 100644
--- a/drivers/iommu/amd/iommu_v2.c
+++ b/drivers/iommu/amd/iommu_v2.c
@@ -485,8 +485,8 @@ static void do_fault(struct work_struct *work)
 	flags |= FAULT_FLAG_REMOTE;
 
 	mmap_read_lock(mm);
-	vma = find_extend_vma(mm, address);
-	if (!vma || address < vma->vm_start)
+	vma = vma_lookup(mm, address);
+	if (!vma)
 		/* failed to get a vma in the right range */
 		goto out;
 
diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 9821bc44f5ac..3ebd4b6586b3 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -175,7 +175,7 @@ iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
 
 	mmap_read_lock(mm);
 
-	vma = find_extend_vma(mm, prm->addr);
+	vma = vma_lookup(mm, prm->addr);
 	if (!vma)
 		/* Unmapped area */
 		goto out_put_mm;
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 983ce34115d5..7b3d2d491407 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -320,10 +320,10 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec,
 	 * Grow the stack manually; some architectures have a limit on how
 	 * far ahead a user-space access may be in order to grow the stack.
 	 */
-	if (mmap_read_lock_killable(mm))
+	if (mmap_write_lock_killable(mm))
 		return -EINTR;
-	vma = find_extend_vma(mm, bprm->p);
-	mmap_read_unlock(mm);
+	vma = find_extend_vma_locked(mm, bprm->p);
+	mmap_write_unlock(mm);
 	if (!vma)
 		return -EFAULT;
 
diff --git a/fs/exec.c b/fs/exec.c
index 25c65b64544b..80b8611c416d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -200,33 +200,39 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 		int write)
 {
 	struct page *page;
+	struct vm_area_struct *vma = bprm->vma;
+	struct mm_struct *mm = bprm->mm;
 	int ret;
-	unsigned int gup_flags = 0;
 
-#ifdef CONFIG_STACK_GROWSUP
-	if (write) {
-		ret = expand_downwards(bprm->vma, pos);
-		if (ret < 0)
+	/*
+	 * Avoid relying on expanding the stack down in GUP (which
+	 * does not work for STACK_GROWSUP anyway), and just do it
+	 * by hand ahead of time.
+	 */
+	if (write && pos < vma->vm_start) {
+		mmap_write_lock(mm);
+		ret = expand_downwards(vma, pos);
+		if (unlikely(ret < 0)) {
+			mmap_write_unlock(mm);
 			return NULL;
-	}
-#endif
-
-	if (write)
-		gup_flags |= FOLL_WRITE;
+		}
+		mmap_write_downgrade(mm);
+	} else
+		mmap_read_lock(mm);
 
 	/*
 	 * We are doing an exec().  'current' is the process
-	 * doing the exec and bprm->mm is the new process's mm.
+	 * doing the exec and 'mm' is the new process's mm.
 	 */
-	mmap_read_lock(bprm->mm);
-	ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
+	ret = get_user_pages_remote(mm, pos, 1,
+			write ? FOLL_WRITE : 0,
 			&page, NULL);
-	mmap_read_unlock(bprm->mm);
+	mmap_read_unlock(mm);
 	if (ret <= 0)
 		return NULL;
 
 	if (write)
-		acct_arg_size(bprm, vma_pages(bprm->vma));
+		acct_arg_size(bprm, vma_pages(vma));
 
 	return page;
 }
@@ -853,7 +859,7 @@ int setup_arg_pages(struct linux_binprm *bprm,
 	stack_base = vma->vm_end - stack_expand;
 #endif
 	current->mm->start_stack = bprm->p;
-	ret = expand_stack(vma, stack_base);
+	ret = expand_stack_locked(vma, stack_base);
 	if (ret)
 		ret = -EFAULT;
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index eef34f6a0351..39aa409e84d5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2334,6 +2334,8 @@ void unmap_mapping_pages(struct address_space *mapping,
 		pgoff_t start, pgoff_t nr, bool even_cows);
 void unmap_mapping_range(struct address_space *mapping,
 		loff_t const holebegin, loff_t const holelen, int even_cows);
+struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
+		unsigned long address, struct pt_regs *regs);
 #else
 static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
 					 unsigned long address, unsigned int flags,
@@ -3228,16 +3230,11 @@ extern vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf);
 
 extern unsigned long stack_guard_gap;
 /* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */
-extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
+int expand_stack_locked(struct vm_area_struct *vma, unsigned long address);
+struct vm_area_struct *expand_stack(struct mm_struct * mm, unsigned long addr);
 
 /* CONFIG_STACK_GROWSUP still needs to grow downwards at some places */
-extern int expand_downwards(struct vm_area_struct *vma,
-		unsigned long address);
-#if VM_GROWSUP
-extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
-#else
-  #define expand_upwards(vma, address) (0)
-#endif
+int expand_downwards(struct vm_area_struct *vma, unsigned long address);
 
 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
 extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);
@@ -3332,7 +3329,8 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
 			unsigned long start, unsigned long end);
 #endif
 
-struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
+struct vm_area_struct *find_extend_vma_locked(struct mm_struct *,
+		unsigned long addr);
 int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
 			unsigned long pfn, unsigned long size, pgprot_t);
 int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
diff --git a/mm/Kconfig b/mm/Kconfig
index 12f32f8d26bf..e00df648c91d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1222,6 +1222,10 @@ config PER_VMA_LOCK
 	  This feature allows locking each virtual memory area separately when
 	  handling page faults instead of taking mmap_lock.
 
+config LOCK_MM_AND_FIND_VMA
+	bool
+	depends on !STACK_GROWSUP
+
 source "mm/damon/Kconfig"
 
 endmenu
diff --git a/mm/gup.c b/mm/gup.c
index 48c1659314b0..ef29641671c7 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1168,7 +1168,11 @@ static long __get_user_pages(struct mm_struct *mm,
 
 		/* first iteration or cross vma bound */
 		if (!vma || start >= vma->vm_end) {
-			vma = find_extend_vma(mm, start);
+			vma = find_vma(mm, start);
+			if (vma && (start < vma->vm_start)) {
+				WARN_ON_ONCE(vma->vm_flags & VM_GROWSDOWN);
+				vma = NULL;
+			}
 			if (!vma && in_gate_area(mm, start)) {
 				ret = get_gate_page(mm, start & PAGE_MASK,
 						gup_flags, &vma,
@@ -1333,9 +1337,13 @@ int fixup_user_fault(struct mm_struct *mm,
 		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 retry:
-	vma = find_extend_vma(mm, address);
-	if (!vma || address < vma->vm_start)
+	vma = find_vma(mm, address);
+	if (!vma)
+		return -EFAULT;
+	if (address < vma->vm_start ) {
+		WARN_ON_ONCE(vma->vm_flags & VM_GROWSDOWN);
 		return -EFAULT;
+	}
 
 	if (!vma_permits_fault(vma, fault_flags))
 		return -EFAULT;
diff --git a/mm/memory.c b/mm/memory.c
index 58029fd5adda..d8a9a770b1f1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5245,6 +5245,125 @@ out:
 }
 EXPORT_SYMBOL_GPL(handle_mm_fault);
 
+#ifdef CONFIG_LOCK_MM_AND_FIND_VMA
+#include <linux/extable.h>
+
+static inline bool get_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs *regs)
+{
+	/* Even if this succeeds, make it clear we *might* have slept */
+	if (likely(mmap_read_trylock(mm))) {
+		might_sleep();
+		return true;
+	}
+
+	if (regs && !user_mode(regs)) {
+		unsigned long ip = instruction_pointer(regs);
+		if (!search_exception_tables(ip))
+			return false;
+	}
+
+	return !mmap_read_lock_killable(mm);
+}
+
+static inline bool mmap_upgrade_trylock(struct mm_struct *mm)
+{
+	/*
+	 * We don't have this operation yet.
+	 *
+	 * It should be easy enough to do: it's basically a
+	 *    atomic_long_try_cmpxchg_acquire()
+	 * from RWSEM_READER_BIAS -> RWSEM_WRITER_LOCKED, but
+	 * it also needs the proper lockdep magic etc.
+	 */
+	return false;
+}
+
+static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs *regs)
+{
+	mmap_read_unlock(mm);
+	if (regs && !user_mode(regs)) {
+		unsigned long ip = instruction_pointer(regs);
+		if (!search_exception_tables(ip))
+			return false;
+	}
+	return !mmap_write_lock_killable(mm);
+}
+
+/*
+ * Helper for page fault handling.
+ *
+ * This is kind of equivalend to "mmap_read_lock()" followed
+ * by "find_extend_vma()", except it's a lot more careful about
+ * the locking (and will drop the lock on failure).
+ *
+ * For example, if we have a kernel bug that causes a page
+ * fault, we don't want to just use mmap_read_lock() to get
+ * the mm lock, because that would deadlock if the bug were
+ * to happen while we're holding the mm lock for writing.
+ *
+ * So this checks the exception tables on kernel faults in
+ * order to only do this all for instructions that are actually
+ * expected to fault.
+ *
+ * We can also actually take the mm lock for writing if we
+ * need to extend the vma, which helps the VM layer a lot.
+ */
+struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
+			unsigned long addr, struct pt_regs *regs)
+{
+	struct vm_area_struct *vma;
+
+	if (!get_mmap_lock_carefully(mm, regs))
+		return NULL;
+
+	vma = find_vma(mm, addr);
+	if (likely(vma && (vma->vm_start <= addr)))
+		return vma;
+
+	/*
+	 * Well, dang. We might still be successful, but only
+	 * if we can extend a vma to do so.
+	 */
+	if (!vma || !(vma->vm_flags & VM_GROWSDOWN)) {
+		mmap_read_unlock(mm);
+		return NULL;
+	}
+
+	/*
+	 * We can try to upgrade the mmap lock atomically,
+	 * in which case we can continue to use the vma
+	 * we already looked up.
+	 *
+	 * Otherwise we'll have to drop the mmap lock and
+	 * re-take it, and also look up the vma again,
+	 * re-checking it.
+	 */
+	if (!mmap_upgrade_trylock(mm)) {
+		if (!upgrade_mmap_lock_carefully(mm, regs))
+			return NULL;
+
+		vma = find_vma(mm, addr);
+		if (!vma)
+			goto fail;
+		if (vma->vm_start <= addr)
+			goto success;
+		if (!(vma->vm_flags & VM_GROWSDOWN))
+			goto fail;
+	}
+
+	if (expand_stack_locked(vma, addr))
+		goto fail;
+
+success:
+	mmap_write_downgrade(mm);
+	return vma;
+
+fail:
+	mmap_write_unlock(mm);
+	return NULL;
+}
+#endif
+
 #ifdef CONFIG_PER_VMA_LOCK
 /*
  * Lookup and lock a VMA under RCU protection. Returned VMA is guaranteed to be
@@ -5584,25 +5703,32 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
 							     gup_flags, &vma);
 
 		if (IS_ERR_OR_NULL(page)) {
-#ifndef CONFIG_HAVE_IOREMAP_PROT
-			break;
-#else
-			int res = 0;
+			/* We might need to expand the stack to access it */
+			vma = vma_lookup(mm, addr);
+			if (!vma) {
+				vma = expand_stack(mm, addr);
+
+				/* mmap_lock was dropped on failure */
+				if (!vma)
+					return buf - old_buf;
+
+				/* Try again if stack expansion worked */
+				continue;
+			}
+
 
 			/*
 			 * Check if this is a VM_IO | VM_PFNMAP VMA, which
 			 * we can access using slightly different code.
 			 */
-			vma = vma_lookup(mm, addr);
-			if (!vma)
-				break;
+			bytes = 0;
+#ifdef CONFIG_HAVE_IOREMAP_PROT
 			if (vma->vm_ops && vma->vm_ops->access)
-				res = vma->vm_ops->access(vma, addr, buf,
-							  len, write);
-			if (res <= 0)
-				break;
-			bytes = res;
+				bytes = vma->vm_ops->access(vma, addr, buf,
+							    len, write);
 #endif
+			if (bytes <= 0)
+				break;
 		} else {
 			bytes = len;
 			offset = addr & (PAGE_SIZE-1);
diff --git a/mm/mmap.c b/mm/mmap.c
index 8f1000bc35df..9b5188b65800 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1948,7 +1948,7 @@ static int acct_stack_growth(struct vm_area_struct *vma,
  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
  * vma is the last one with address > vma->vm_end.  Have to extend vma.
  */
-int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+static int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct vm_area_struct *next;
@@ -2040,6 +2040,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 
 /*
  * vma is the first one with address < vma->vm_start.  Have to extend vma.
+ * mmap_lock held for writing.
  */
 int expand_downwards(struct vm_area_struct *vma, unsigned long address)
 {
@@ -2048,16 +2049,20 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address)
 	struct vm_area_struct *prev;
 	int error = 0;
 
+	if (!(vma->vm_flags & VM_GROWSDOWN))
+		return -EFAULT;
+
 	address &= PAGE_MASK;
-	if (address < mmap_min_addr)
+	if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
 		return -EPERM;
 
 	/* Enforce stack_guard_gap */
 	prev = mas_prev(&mas, 0);
 	/* Check that both stack segments have the same anon_vma? */
-	if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
-			vma_is_accessible(prev)) {
-		if (address - prev->vm_end < stack_guard_gap)
+	if (prev) {
+		if (!(prev->vm_flags & VM_GROWSDOWN) &&
+		    vma_is_accessible(prev) &&
+		    (address - prev->vm_end < stack_guard_gap))
 			return -ENOMEM;
 	}
 
@@ -2137,13 +2142,12 @@ static int __init cmdline_parse_stack_guard_gap(char *p)
 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
 
 #ifdef CONFIG_STACK_GROWSUP
-int expand_stack(struct vm_area_struct *vma, unsigned long address)
+int expand_stack_locked(struct vm_area_struct *vma, unsigned long address)
 {
 	return expand_upwards(vma, address);
 }
 
-struct vm_area_struct *
-find_extend_vma(struct mm_struct *mm, unsigned long addr)
+struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr)
 {
 	struct vm_area_struct *vma, *prev;
 
@@ -2151,20 +2155,23 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
 	vma = find_vma_prev(mm, addr, &prev);
 	if (vma && (vma->vm_start <= addr))
 		return vma;
-	if (!prev || expand_stack(prev, addr))
+	if (!prev)
+		return NULL;
+	if (expand_stack_locked(prev, addr))
 		return NULL;
 	if (prev->vm_flags & VM_LOCKED)
 		populate_vma_page_range(prev, addr, prev->vm_end, NULL);
 	return prev;
 }
 #else
-int expand_stack(struct vm_area_struct *vma, unsigned long address)
+int expand_stack_locked(struct vm_area_struct *vma, unsigned long address)
 {
+	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
+		return -EINVAL;
 	return expand_downwards(vma, address);
 }
 
-struct vm_area_struct *
-find_extend_vma(struct mm_struct *mm, unsigned long addr)
+struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr)
 {
 	struct vm_area_struct *vma;
 	unsigned long start;
@@ -2175,10 +2182,8 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
 		return NULL;
 	if (vma->vm_start <= addr)
 		return vma;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		return NULL;
 	start = vma->vm_start;
-	if (expand_stack(vma, addr))
+	if (expand_stack_locked(vma, addr))
 		return NULL;
 	if (vma->vm_flags & VM_LOCKED)
 		populate_vma_page_range(vma, addr, start, NULL);
@@ -2186,7 +2191,91 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
 }
 #endif
 
-EXPORT_SYMBOL_GPL(find_extend_vma);
+/*
+ * IA64 has some horrid mapping rules: it can expand both up and down,
+ * but with various special rules.
+ *
+ * We'll get rid of this architecture eventually, so the ugliness is
+ * temporary.
+ */
+#ifdef CONFIG_IA64
+static inline bool vma_expand_ok(struct vm_area_struct *vma, unsigned long addr)
+{
+	return REGION_NUMBER(addr) == REGION_NUMBER(vma->vm_start) &&
+		REGION_OFFSET(addr) < RGN_MAP_LIMIT;
+}
+
+/*
+ * IA64 stacks grow down, but there's a special register backing store
+ * that can grow up. Only sequentially, though, so the new address must
+ * match vm_end.
+ */
+static inline int vma_expand_up(struct vm_area_struct *vma, unsigned long addr)
+{
+	if (!vma_expand_ok(vma, addr))
+		return -EFAULT;
+	if (vma->vm_end != (addr & PAGE_MASK))
+		return -EFAULT;
+	return expand_upwards(vma, addr);
+}
+
+static inline bool vma_expand_down(struct vm_area_struct *vma, unsigned long addr)
+{
+	if (!vma_expand_ok(vma, addr))
+		return -EFAULT;
+	return expand_downwards(vma, addr);
+}
+
+#elif defined(CONFIG_STACK_GROWSUP)
+
+#define vma_expand_up(vma,addr) expand_upwards(vma, addr)
+#define vma_expand_down(vma, addr) (-EFAULT)
+
+#else
+
+#define vma_expand_up(vma,addr) (-EFAULT)
+#define vma_expand_down(vma, addr) expand_downwards(vma, addr)
+
+#endif
+
+/*
+ * expand_stack(): legacy interface for page faulting. Don't use unless
+ * you have to.
+ *
+ * This is called with the mm locked for reading, drops the lock, takes
+ * the lock for writing, tries to look up a vma again, expands it if
+ * necessary, and downgrades the lock to reading again.
+ *
+ * If no vma is found or it can't be expanded, it returns NULL and has
+ * dropped the lock.
+ */
+struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
+{
+	struct vm_area_struct *vma, *prev;
+
+	mmap_read_unlock(mm);
+	if (mmap_write_lock_killable(mm))
+		return NULL;
+
+	vma = find_vma_prev(mm, addr, &prev);
+	if (vma && vma->vm_start <= addr)
+		goto success;
+
+	if (prev && !vma_expand_up(prev, addr)) {
+		vma = prev;
+		goto success;
+	}
+
+	if (vma && !vma_expand_down(vma, addr))
+		goto success;
+
+	mmap_write_unlock(mm);
+	return NULL;
+
+success:
+	mmap_write_downgrade(mm);
+	return vma;
+}
 
 /*
  * Ok - we have the memory areas we should free on a maple tree so release them,
diff --git a/mm/nommu.c b/mm/nommu.c
index f670d9979a26..37d0b03143f1 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -631,23 +631,20 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 EXPORT_SYMBOL(find_vma);
 
 /*
- * find a VMA
- * - we don't extend stack VMAs under NOMMU conditions
- */
-struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
-{
-	return find_vma(mm, addr);
-}
-
-/*
  * expand a stack to a given address
  * - not supported under NOMMU conditions
  */
-int expand_stack(struct vm_area_struct *vma, unsigned long address)
+int expand_stack_locked(struct vm_area_struct *vma, unsigned long addr)
 {
 	return -ENOMEM;
 }
 
+struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
+{
+	mmap_read_unlock(mm);
+	return NULL;
+}
+
 /*
  * look up the first VMA exactly that exactly matches addr
  * - should be called with mm->mmap_lock at least held readlocked