Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull exit cleanups from Eric Biederman:
 "While looking at some issues related to the exit path in the kernel I
  found several instances where the code is not using the existing
  abstractions properly.

  This set of changes introduces force_fatal_sig a way of sending a
  signal and not allowing it to be caught, and corrects the misuse of
  the existing abstractions that I found.

  A lot of the misuse of the existing abstractions are silly things such
  as doing something after calling a no return function, rolling BUG by
  hand, doing more work than necessary to terminate a kernel thread, or
  calling do_exit(SIGKILL) instead of calling force_sig(SIGKILL).

  In the review a deficiency in force_fatal_sig and force_sig_seccomp
  where ptrace or sigaction could prevent the delivery of the signal was
  found. I have added a change that adds SA_IMMUTABLE to change that
  makes it impossible to interrupt the delivery of those signals, and
  allows backporting to fix force_sig_seccomp

  And Arnd found an issue where a function passed to kthread_run had the
  wrong prototype, and after my cleanup was failing to build."

* 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (23 commits)
  soc: ti: fix wkup_m3_rproc_boot_thread return type
  signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed
  signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV)
  exit/r8188eu: Replace the macro thread_exit with a simple return 0
  exit/rtl8712: Replace the macro thread_exit with a simple return 0
  exit/rtl8723bs: Replace the macro thread_exit with a simple return 0
  signal/x86: In emulate_vsyscall force a signal instead of calling do_exit
  signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig
  signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails
  exit/syscall_user_dispatch: Send ordinary signals on failure
  signal: Implement force_fatal_sig
  exit/kthread: Have kernel threads return instead of calling do_exit
  signal/s390: Use force_sigsegv in default_trap_handler
  signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.
  signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON
  signal/sparc: In setup_tsb_params convert open coded BUG into BUG
  signal/powerpc: On swapcontext failure force SIGSEGV
  signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL)
  signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT
  signal/sparc32: Remove unreachable do_exit in do_sparc_fault
  ...

4 files changed, 3 insertions, 5 deletions

diff --git a/arch/s390/include/asm/kdebug.h b/arch/s390/include/asm/kdebug.h
index d5327f064799..4377238e4752 100644
--- a/arch/s390/include/asm/kdebug.h
+++ b/arch/s390/include/asm/kdebug.h
@@ -23,6 +23,6 @@ enum die_val {
 	DIE_NMI_IPI,
 };
 
-extern void die(struct pt_regs *, const char *);
+extern void __noreturn die(struct pt_regs *, const char *);
 
 #endif
diff --git a/arch/s390/kernel/dumpstack.c b/arch/s390/kernel/dumpstack.c
index 85f326e258df..0681c55e831d 100644
--- a/arch/s390/kernel/dumpstack.c
+++ b/arch/s390/kernel/dumpstack.c
@@ -192,7 +192,7 @@ void show_regs(struct pt_regs *regs)
 
 static DEFINE_SPINLOCK(die_lock);
 
-void die(struct pt_regs *regs, const char *str)
+void __noreturn die(struct pt_regs *regs, const char *str)
 {
 	static int die_counter;
 
diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
index 6c6f7dcce1a5..035705c9f23e 100644
--- a/arch/s390/kernel/traps.c
+++ b/arch/s390/kernel/traps.c
@@ -84,7 +84,7 @@ static void default_trap_handler(struct pt_regs *regs)
 {
 	if (user_mode(regs)) {
 		report_user_fault(regs, SIGSEGV, 0);
-		do_exit(SIGSEGV);
+		force_fatal_sig(SIGSEGV);
 	} else
 		die(regs, "Unknown program exception");
 }
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 212632d57db9..d30f5986fa85 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -260,7 +260,6 @@ static noinline void do_no_context(struct pt_regs *regs)
 		       " in virtual user address space\n");
 	dump_fault_info(regs);
 	die(regs, "Oops");
-	do_exit(SIGKILL);
 }
 
 static noinline void do_low_address(struct pt_regs *regs)
@@ -270,7 +269,6 @@ static noinline void do_low_address(struct pt_regs *regs)
 	if (regs->psw.mask & PSW_MASK_PSTATE) {
 		/* Low-address protection hit in user mode 'cannot happen'. */
 		die (regs, "Low-address protection");
-		do_exit(SIGKILL);
 	}
 
 	do_no_context(regs);