This is a note to let you know that I've just added the patch titled signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: signal-mips-update-_save-_restore-_fp_context-to-fail-with-efault.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 95bf9d646c3c3f95cb0be7e703b371db8da5be68 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Date: Wed, 20 Oct 2021 12:43:51 -0500 Subject: signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> commit 95bf9d646c3c3f95cb0be7e703b371db8da5be68 upstream. When an instruction to save or restore a register from the stack fails in _save_fp_context or _restore_fp_context return with -EFAULT. This change was made to r2300_fpu.S[1] but it looks like it got lost with the introduction of EX2[2]. This is also what the other implementation of _save_fp_context and _restore_fp_context in r4k_fpu.S does, and what is needed for the callers to be able to handle the error. Furthermore calling do_exit(SIGSEGV) from bad_stack is wrong because it does not terminate the entire process it just terminates a single thread. As the changed code was the only caller of arch/mips/kernel/syscall.c:bad_stack remove the problematic and now unused helper function. Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Cc: Maciej Rozycki <macro@xxxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxxx [1] 35938a00ba86 ("MIPS: Fix ISA I FP sigcontext access violation handling") [2] f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout") Cc: stable@xxxxxxxxxxxxxxx Fixes: f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout") Acked-by: Maciej W. Rozycki <macro@xxxxxxxxxxx> Acked-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20211020174406.17889-5-ebiederm@xxxxxxxxxxxx Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/mips/kernel/r2300_fpu.S | 4 ++-- arch/mips/kernel/syscall.c | 9 --------- 2 files changed, 2 insertions(+), 11 deletions(-) --- a/arch/mips/kernel/r2300_fpu.S +++ b/arch/mips/kernel/r2300_fpu.S @@ -29,8 +29,8 @@ #define EX2(a,b) \ 9: a,##b; \ .section __ex_table,"a"; \ - PTR 9b,bad_stack; \ - PTR 9b+4,bad_stack; \ + PTR 9b,fault; \ + PTR 9b+4,fault; \ .previous .set mips1 --- a/arch/mips/kernel/syscall.c +++ b/arch/mips/kernel/syscall.c @@ -240,12 +240,3 @@ SYSCALL_DEFINE3(cachectl, char *, addr, { return -ENOSYS; } - -/* - * If we ever come here the user sp is bad. Zap the process right away. - * Due to the bad stack signaling wouldn't work. - */ -asmlinkage void bad_stack(void) -{ - do_exit(SIGSEGV); -} Patches currently in stable-queue which might be from ebiederm@xxxxxxxxxxxx are queue-5.15/signal-remove-the-bogus-sigkill_pending-in-ptrace_stop.patch queue-5.15/signal-mips-update-_save-_restore-_fp_context-to-fail-with-efault.patch queue-5.15/signal-add-sa_immutable-to-ensure-forced-siganls-do-not-get-changed.patch