From 7d06d9c9bd813fc956b9c7bffc1b9724009983eb Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 29 Jul 2016 09:30:12 -0700 Subject: mm: Implement new pkey_mprotect() system call pkey_mprotect() is just like mprotect, except it also takes a protection key as an argument. On systems that do not support protection keys, it still works, but requires that key=0. Otherwise it does exactly what mprotect does. I expect it to get used like this, if you want to guarantee that any mapping you create can *never* be accessed without the right protection keys set up. int real_prot = PROT_READ|PROT_WRITE; pkey = pkey_alloc(0, PKEY_DENY_ACCESS); ptr = mmap(NULL, PAGE_SIZE, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); ret = pkey_mprotect(ptr, PAGE_SIZE, real_prot, pkey); This way, there is *no* window where the mapping is accessible since it was always either PROT_NONE or had a protection key set that denied all access. We settled on 'unsigned long' for the type of the key here. We only need 4 bits on x86 today, but I figured that other architectures might need some more space. Semantically, we have a bit of a problem if we combine this syscall with our previously-introduced execute-only support: What do we do when we mix execute-only pkey use with pkey_mprotect() use? For instance: pkey_mprotect(ptr, PAGE_SIZE, PROT_WRITE, 6); // set pkey=6 mprotect(ptr, PAGE_SIZE, PROT_EXEC); // set pkey=X_ONLY_PKEY? mprotect(ptr, PAGE_SIZE, PROT_WRITE); // is pkey=6 again? To solve that, we make the plain-mprotect()-initiated execute-only support only apply to VMAs that have the default protection key (0) set on them. Proposed semantics: 1. protection key 0 is special and represents the default, "unassigned" protection key. It is always allocated. 2. mprotect() never affects a mapping's pkey_mprotect()-assigned protection key. A protection key of 0 (even if set explicitly) represents an unassigned protection key. 2a. mprotect(PROT_EXEC) on a mapping with an assigned protection key may or may not result in a mapping with execute-only properties. pkey_mprotect() plus pkey_set() on all threads should be used to _guarantee_ execute-only semantics if this is not a strong enough semantic. 3. mprotect(PROT_EXEC) may result in an "execute-only" mapping. The kernel will internally attempt to allocate and dedicate a protection key for the purpose of execute-only mappings. This may not be possible in cases where there are no free protection keys available. It can also happen, of course, in situations where there is no hardware support for protection keys. Signed-off-by: Dave Hansen Acked-by: Mel Gorman Cc: linux-arch@vger.kernel.org Cc: Dave Hansen Cc: arnd@arndb.de Cc: linux-api@vger.kernel.org Cc: linux-mm@kvack.org Cc: luto@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20160729163012.3DDD36C4@viggo.jf.intel.com Signed-off-by: Thomas Gleixner --- mm/mprotect.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) (limited to 'mm/mprotect.c') diff --git a/mm/mprotect.c b/mm/mprotect.c index a4830f0325fe..dd3f40a2935f 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -352,8 +352,11 @@ fail: return error; } -SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, - unsigned long, prot) +/* + * pkey==-1 when doing a legacy mprotect() + */ +static int do_mprotect_pkey(unsigned long start, size_t len, + unsigned long prot, int pkey) { unsigned long nstart, end, tmp, reqprot; struct vm_area_struct *vma, *prev; @@ -361,6 +364,12 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); const bool rier = (current->personality & READ_IMPLIES_EXEC) && (prot & PROT_READ); + /* + * A temporary safety check since we are not validating + * the pkey before we introduce the allocation code. + */ + if (pkey != -1) + return -EINVAL; prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ @@ -409,7 +418,7 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, for (nstart = start ; ; ) { unsigned long newflags; - int pkey = arch_override_mprotect_pkey(vma, prot, -1); + int new_vma_pkey; /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ @@ -417,7 +426,8 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, if (rier && (vma->vm_flags & VM_MAYEXEC)) prot |= PROT_EXEC; - newflags = calc_vm_prot_bits(prot, pkey); + new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); + newflags = calc_vm_prot_bits(prot, new_vma_pkey); newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); /* newflags >> 4 shift VM_MAY% in place of VM_% */ @@ -454,3 +464,15 @@ out: up_write(¤t->mm->mmap_sem); return error; } + +SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, + unsigned long, prot) +{ + return do_mprotect_pkey(start, len, prot, -1); +} + +SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, + unsigned long, prot, int, pkey) +{ + return do_mprotect_pkey(start, len, prot, pkey); +} -- cgit v1.2.3 From a8502b67d739c1d7a4542c1da0a5d98a6a58c177 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 29 Jul 2016 09:30:13 -0700 Subject: x86/pkeys: Make mprotect_key() mask off additional vm_flags Today, mprotect() takes 4 bits of data: PROT_READ/WRITE/EXEC/NONE. Three of those bits: READ/WRITE/EXEC get translated directly in to vma->vm_flags by calc_vm_prot_bits(). If a bit is unset in mprotect()'s 'prot' argument then it must be cleared in vma->vm_flags during the mprotect() call. We do this clearing today by first calculating the VMA flags we want set, then clearing the ones we do not want to inherit from the original VMA: vm_flags = calc_vm_prot_bits(prot, key); ... newflags = vm_flags; newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); However, we *also* want to mask off the original VMA's vm_flags in which we store the protection key. To do that, this patch adds a new macro: ARCH_VM_PKEY_FLAGS which allows the architecture to specify additional bits that it would like cleared. We use that to ensure that the VM_PKEY_BIT* bits get cleared. Signed-off-by: Dave Hansen Acked-by: Mel Gorman Reviewed-by: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: Dave Hansen Cc: arnd@arndb.de Cc: linux-api@vger.kernel.org Cc: linux-mm@kvack.org Cc: luto@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20160729163013.E48D6981@viggo.jf.intel.com Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/pkeys.h | 2 ++ include/linux/pkeys.h | 1 + mm/mprotect.c | 11 ++++++++++- 3 files changed, 13 insertions(+), 1 deletion(-) (limited to 'mm/mprotect.c') diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index 33777c291a85..666ffc862ef7 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -38,4 +38,6 @@ static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma, extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val); +#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3) + #endif /*_ASM_X86_PKEYS_H */ diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h index 0030b4024559..6899b0bc7ce0 100644 --- a/include/linux/pkeys.h +++ b/include/linux/pkeys.h @@ -16,6 +16,7 @@ #define execute_only_pkey(mm) (0) #define arch_override_mprotect_pkey(vma, prot, pkey) (0) #define PKEY_DEDICATED_EXECUTE_ONLY 0 +#define ARCH_VM_PKEY_FLAGS 0 #endif /* ! CONFIG_ARCH_HAS_PKEYS */ #endif /* _LINUX_PKEYS_H */ diff --git a/mm/mprotect.c b/mm/mprotect.c index dd3f40a2935f..abd9c8257b2e 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -417,6 +417,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len, prev = vma; for (nstart = start ; ; ) { + unsigned long mask_off_old_flags; unsigned long newflags; int new_vma_pkey; @@ -426,9 +427,17 @@ static int do_mprotect_pkey(unsigned long start, size_t len, if (rier && (vma->vm_flags & VM_MAYEXEC)) prot |= PROT_EXEC; + /* + * Each mprotect() call explicitly passes r/w/x permissions. + * If a permission is not passed to mprotect(), it must be + * cleared from the VMA. + */ + mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC | + ARCH_VM_PKEY_FLAGS; + new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); newflags = calc_vm_prot_bits(prot, new_vma_pkey); - newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); + newflags |= (vma->vm_flags & ~mask_off_old_flags); /* newflags >> 4 shift VM_MAY% in place of VM_% */ if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { -- cgit v1.2.3 From e8c24d3a23a469f1f40d4de24d872ca7023ced0a Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 29 Jul 2016 09:30:15 -0700 Subject: x86/pkeys: Allocation/free syscalls This patch adds two new system calls: int pkey_alloc(unsigned long flags, unsigned long init_access_rights) int pkey_free(int pkey); These implement an "allocator" for the protection keys themselves, which can be thought of as analogous to the allocator that the kernel has for file descriptors. The kernel tracks which numbers are in use, and only allows operations on keys that are valid. A key which was not obtained by pkey_alloc() may not, for instance, be passed to pkey_mprotect(). These system calls are also very important given the kernel's use of pkeys to implement execute-only support. These help ensure that userspace can never assume that it has control of a key unless it first asks the kernel. The kernel does not promise to preserve PKRU (right register) contents except for allocated pkeys. The 'init_access_rights' argument to pkey_alloc() specifies the rights that will be established for the returned pkey. For instance: pkey = pkey_alloc(flags, PKEY_DENY_WRITE); will allocate 'pkey', but also sets the bits in PKRU[1] such that writing to 'pkey' is already denied. The kernel does not prevent pkey_free() from successfully freeing in-use pkeys (those still assigned to a memory range by pkey_mprotect()). It would be expensive to implement the checks for this, so we instead say, "Just don't do it" since sane software will never do it anyway. Any piece of userspace calling pkey_alloc() needs to be prepared for it to fail. Why? pkey_alloc() returns the same error code (ENOSPC) when there are no pkeys and when pkeys are unsupported. They can be unsupported for a whole host of reasons, so apps must be prepared for this. Also, libraries or LD_PRELOADs might steal keys before an application gets access to them. This allocation mechanism could be implemented in userspace. Even if we did it in userspace, we would still need additional user/kernel interfaces to tell userspace which keys are being used by the kernel internally (such as for execute-only mappings). Having the kernel provide this facility completely removes the need for these additional interfaces, or having an implementation of this in userspace at all. Note that we have to make changes to all of the architectures that do not use mman-common.h because we use the new PKEY_DENY_ACCESS/WRITE macros in arch-independent code. 1. PKRU is the Protection Key Rights User register. It is a usermode-accessible register that controls whether writes and/or access to each individual pkey is allowed or denied. Signed-off-by: Dave Hansen Acked-by: Mel Gorman Cc: linux-arch@vger.kernel.org Cc: Dave Hansen Cc: arnd@arndb.de Cc: linux-api@vger.kernel.org Cc: linux-mm@kvack.org Cc: luto@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20160729163015.444FE75F@viggo.jf.intel.com Signed-off-by: Thomas Gleixner --- arch/alpha/include/uapi/asm/mman.h | 5 +++ arch/mips/include/uapi/asm/mman.h | 5 +++ arch/parisc/include/uapi/asm/mman.h | 5 +++ arch/x86/include/asm/mmu.h | 8 ++++ arch/x86/include/asm/mmu_context.h | 10 ++++- arch/x86/include/asm/pkeys.h | 73 +++++++++++++++++++++++++++++++--- arch/x86/kernel/fpu/xstate.c | 5 ++- arch/x86/mm/pkeys.c | 38 ++++++++++++++---- arch/xtensa/include/uapi/asm/mman.h | 5 +++ include/linux/pkeys.h | 28 ++++++++++--- include/uapi/asm-generic/mman-common.h | 5 +++ mm/mprotect.c | 61 +++++++++++++++++++++++++--- 12 files changed, 221 insertions(+), 27 deletions(-) (limited to 'mm/mprotect.c') diff --git a/arch/alpha/include/uapi/asm/mman.h b/arch/alpha/include/uapi/asm/mman.h index fec1947b8dbc..02760f6e6ca4 100644 --- a/arch/alpha/include/uapi/asm/mman.h +++ b/arch/alpha/include/uapi/asm/mman.h @@ -78,4 +78,9 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define PKEY_DISABLE_ACCESS 0x1 +#define PKEY_DISABLE_WRITE 0x2 +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ + PKEY_DISABLE_WRITE) + #endif /* __ALPHA_MMAN_H__ */ diff --git a/arch/mips/include/uapi/asm/mman.h b/arch/mips/include/uapi/asm/mman.h index ccdcfcbb24aa..655e2fb5395b 100644 --- a/arch/mips/include/uapi/asm/mman.h +++ b/arch/mips/include/uapi/asm/mman.h @@ -105,4 +105,9 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define PKEY_DISABLE_ACCESS 0x1 +#define PKEY_DISABLE_WRITE 0x2 +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ + PKEY_DISABLE_WRITE) + #endif /* _ASM_MMAN_H */ diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h index f3db7d8eb0c2..5979745815a5 100644 --- a/arch/parisc/include/uapi/asm/mman.h +++ b/arch/parisc/include/uapi/asm/mman.h @@ -75,4 +75,9 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define PKEY_DISABLE_ACCESS 0x1 +#define PKEY_DISABLE_WRITE 0x2 +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ + PKEY_DISABLE_WRITE) + #endif /* __PARISC_MMAN_H__ */ diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 1ea0baef1175..72198c64e646 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -23,6 +23,14 @@ typedef struct { const struct vdso_image *vdso_image; /* vdso image in use */ atomic_t perf_rdpmc_allowed; /* nonzero if rdpmc is allowed */ +#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS + /* + * One bit per protection key says whether userspace can + * use it or not. protected by mmap_sem. + */ + u16 pkey_allocation_map; + s16 execute_only_pkey; +#endif } mm_context_t; #ifdef CONFIG_SMP diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index af0251fc85ed..8e0a9fe86de4 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -108,7 +108,16 @@ static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm) { + #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS + if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { + /* pkey 0 is the default and always allocated */ + mm->context.pkey_allocation_map = 0x1; + /* -1 means unallocated or invalid */ + mm->context.execute_only_pkey = -1; + } + #endif init_new_context_ldt(tsk, mm); + return 0; } static inline void destroy_context(struct mm_struct *mm) @@ -263,5 +272,4 @@ static inline bool arch_pte_access_permitted(pte_t pte, bool write) { return __pkru_allows_pkey(pte_flags_pkey(pte_flags(pte)), write); } - #endif /* _ASM_X86_MMU_CONTEXT_H */ diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index 666ffc862ef7..b406889de0db 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -1,12 +1,7 @@ #ifndef _ASM_X86_PKEYS_H #define _ASM_X86_PKEYS_H -#define PKEY_DEDICATED_EXECUTE_ONLY 15 -/* - * Consider the PKEY_DEDICATED_EXECUTE_ONLY key unavailable. - */ -#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? \ - PKEY_DEDICATED_EXECUTE_ONLY : 1) +#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? 16 : 1) extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val); @@ -40,4 +35,70 @@ extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, #define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3) +#define mm_pkey_allocation_map(mm) (mm->context.pkey_allocation_map) +#define mm_set_pkey_allocated(mm, pkey) do { \ + mm_pkey_allocation_map(mm) |= (1U << pkey); \ +} while (0) +#define mm_set_pkey_free(mm, pkey) do { \ + mm_pkey_allocation_map(mm) &= ~(1U << pkey); \ +} while (0) + +static inline +bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey) +{ + return mm_pkey_allocation_map(mm) & (1U << pkey); +} + +/* + * Returns a positive, 4-bit key on success, or -1 on failure. + */ +static inline +int mm_pkey_alloc(struct mm_struct *mm) +{ + /* + * Note: this is the one and only place we make sure + * that the pkey is valid as far as the hardware is + * concerned. The rest of the kernel trusts that + * only good, valid pkeys come out of here. + */ + u16 all_pkeys_mask = ((1U << arch_max_pkey()) - 1); + int ret; + + /* + * Are we out of pkeys? We must handle this specially + * because ffz() behavior is undefined if there are no + * zeros. + */ + if (mm_pkey_allocation_map(mm) == all_pkeys_mask) + return -1; + + ret = ffz(mm_pkey_allocation_map(mm)); + + mm_set_pkey_allocated(mm, ret); + + return ret; +} + +static inline +int mm_pkey_free(struct mm_struct *mm, int pkey) +{ + /* + * pkey 0 is special, always allocated and can never + * be freed. + */ + if (!pkey) + return -EINVAL; + if (!mm_pkey_is_allocated(mm, pkey)) + return -EINVAL; + + mm_set_pkey_free(mm, pkey); + + return 0; +} + +extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, + unsigned long init_val); +extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, + unsigned long init_val); + #endif /*_ASM_X86_PKEYS_H */ diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 01567aa87503..124aa5c593f8 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -5,6 +5,7 @@ */ #include #include +#include #include #include @@ -866,9 +867,10 @@ const void *get_xsave_field_ptr(int xsave_state) return get_xsave_addr(&fpu->state.xsave, xsave_state); } +#ifdef CONFIG_ARCH_HAS_PKEYS + #define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2) #define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1) - /* * This will go out and modify PKRU register to set the access * rights for @pkey to @init_val. @@ -914,6 +916,7 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, return 0; } +#endif /* ! CONFIG_ARCH_HAS_PKEYS */ /* * This is similar to user_regset_copyout(), but will not add offset to diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c index e8c474451928..e6113bbb56e1 100644 --- a/arch/x86/mm/pkeys.c +++ b/arch/x86/mm/pkeys.c @@ -21,8 +21,19 @@ int __execute_only_pkey(struct mm_struct *mm) { + bool need_to_set_mm_pkey = false; + int execute_only_pkey = mm->context.execute_only_pkey; int ret; + /* Do we need to assign a pkey for mm's execute-only maps? */ + if (execute_only_pkey == -1) { + /* Go allocate one to use, which might fail */ + execute_only_pkey = mm_pkey_alloc(mm); + if (execute_only_pkey < 0) + return -1; + need_to_set_mm_pkey = true; + } + /* * We do not want to go through the relatively costly * dance to set PKRU if we do not need to. Check it @@ -32,22 +43,33 @@ int __execute_only_pkey(struct mm_struct *mm) * can make fpregs inactive. */ preempt_disable(); - if (fpregs_active() && - !__pkru_allows_read(read_pkru(), PKEY_DEDICATED_EXECUTE_ONLY)) { + if (!need_to_set_mm_pkey && + fpregs_active() && + !__pkru_allows_read(read_pkru(), execute_only_pkey)) { preempt_enable(); - return PKEY_DEDICATED_EXECUTE_ONLY; + return execute_only_pkey; } preempt_enable(); - ret = arch_set_user_pkey_access(current, PKEY_DEDICATED_EXECUTE_ONLY, + + /* + * Set up PKRU so that it denies access for everything + * other than execution. + */ + ret = arch_set_user_pkey_access(current, execute_only_pkey, PKEY_DISABLE_ACCESS); /* * If the PKRU-set operation failed somehow, just return * 0 and effectively disable execute-only support. */ - if (ret) - return 0; + if (ret) { + mm_set_pkey_free(mm, execute_only_pkey); + return -1; + } - return PKEY_DEDICATED_EXECUTE_ONLY; + /* We got one, store it and use it from here on out */ + if (need_to_set_mm_pkey) + mm->context.execute_only_pkey = execute_only_pkey; + return execute_only_pkey; } static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma) @@ -55,7 +77,7 @@ static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma) /* Do this check first since the vm_flags should be hot */ if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC) return false; - if (vma_pkey(vma) != PKEY_DEDICATED_EXECUTE_ONLY) + if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey) return false; return true; diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h index 9e079d49e7f2..24365b30aae9 100644 --- a/arch/xtensa/include/uapi/asm/mman.h +++ b/arch/xtensa/include/uapi/asm/mman.h @@ -117,4 +117,9 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define PKEY_DISABLE_ACCESS 0x1 +#define PKEY_DISABLE_WRITE 0x2 +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ + PKEY_DISABLE_WRITE) + #endif /* _XTENSA_MMAN_H */ diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h index 6899b0bc7ce0..8ff21125dc8a 100644 --- a/include/linux/pkeys.h +++ b/include/linux/pkeys.h @@ -4,11 +4,6 @@ #include #include -#define PKEY_DISABLE_ACCESS 0x1 -#define PKEY_DISABLE_WRITE 0x2 -#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ - PKEY_DISABLE_WRITE) - #ifdef CONFIG_ARCH_HAS_PKEYS #include #else /* ! CONFIG_ARCH_HAS_PKEYS */ @@ -17,6 +12,29 @@ #define arch_override_mprotect_pkey(vma, prot, pkey) (0) #define PKEY_DEDICATED_EXECUTE_ONLY 0 #define ARCH_VM_PKEY_FLAGS 0 + +static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey) +{ + return (pkey == 0); +} + +static inline int mm_pkey_alloc(struct mm_struct *mm) +{ + return -1; +} + +static inline int mm_pkey_free(struct mm_struct *mm, int pkey) +{ + WARN_ONCE(1, "free of protection key when disabled"); + return -EINVAL; +} + +static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, + unsigned long init_val) +{ + return 0; +} + #endif /* ! CONFIG_ARCH_HAS_PKEYS */ #endif /* _LINUX_PKEYS_H */ diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h index 58274382a616..8c27db0c5c08 100644 --- a/include/uapi/asm-generic/mman-common.h +++ b/include/uapi/asm-generic/mman-common.h @@ -72,4 +72,9 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define PKEY_DISABLE_ACCESS 0x1 +#define PKEY_DISABLE_WRITE 0x2 +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ + PKEY_DISABLE_WRITE) + #endif /* __ASM_GENERIC_MMAN_COMMON_H */ diff --git a/mm/mprotect.c b/mm/mprotect.c index abd9c8257b2e..7b35ee3894ee 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -23,11 +23,13 @@ #include #include #include +#include #include #include #include #include #include +#include #include #include "internal.h" @@ -364,12 +366,6 @@ static int do_mprotect_pkey(unsigned long start, size_t len, const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); const bool rier = (current->personality & READ_IMPLIES_EXEC) && (prot & PROT_READ); - /* - * A temporary safety check since we are not validating - * the pkey before we introduce the allocation code. - */ - if (pkey != -1) - return -EINVAL; prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ @@ -391,6 +387,14 @@ static int do_mprotect_pkey(unsigned long start, size_t len, if (down_write_killable(¤t->mm->mmap_sem)) return -EINTR; + /* + * If userspace did not allocate the pkey, do not let + * them use it here. + */ + error = -EINVAL; + if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey)) + goto out; + vma = find_vma(current->mm, start); error = -ENOMEM; if (!vma) @@ -485,3 +489,48 @@ SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, { return do_mprotect_pkey(start, len, prot, pkey); } + +SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val) +{ + int pkey; + int ret; + + /* No flags supported yet. */ + if (flags) + return -EINVAL; + /* check for unsupported init values */ + if (init_val & ~PKEY_ACCESS_MASK) + return -EINVAL; + + down_write(¤t->mm->mmap_sem); + pkey = mm_pkey_alloc(current->mm); + + ret = -ENOSPC; + if (pkey == -1) + goto out; + + ret = arch_set_user_pkey_access(current, pkey, init_val); + if (ret) { + mm_pkey_free(current->mm, pkey); + goto out; + } + ret = pkey; +out: + up_write(¤t->mm->mmap_sem); + return ret; +} + +SYSCALL_DEFINE1(pkey_free, int, pkey) +{ + int ret; + + down_write(¤t->mm->mmap_sem); + ret = mm_pkey_free(current->mm, pkey); + up_write(¤t->mm->mmap_sem); + + /* + * We could provie warnings or errors if any VMA still + * has the pkey set here. + */ + return ret; +} -- cgit v1.2.3