# \[PATCH 4.9 043/207\] signal/mips: Update (\_save\|\_restore)\_fp\_context to fail with -EFAULT - From: Greg Kroah-Hartman \ - Date: 2021-11-24 12:16:07 - List: linux-mips - Page: https://ratatoskr.run/linux-mips/2021/11/1583963 - Thread: https://ratatoskr.run/stable/2021/11/1583929/t.md ```text From: Eric W. Biederman 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 Cc: Maciej Rozycki Cc: [1] 35938a00ba86 ("MIPS: Fix ISA I FP sigcontext access violation handling") [2] f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout") Cc: Fixes: f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout") Acked-by: Maciej W. Rozycki Acked-by: Thomas Bogendoerfer Link: https://lkml.kernel.org/r/20211020174406.17889-5-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Greg Kroah-Hartman --- 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 @@ -27,8 +27,8 @@ #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 noreorder --- a/arch/mips/kernel/syscall.c +++ b/arch/mips/kernel/syscall.c @@ -244,12 +244,3 @@ 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); -} ```