Commit ba3f578b authored Oct 20, 2021 by Eric W. Biederman Committed by Greg Kroah-Hartman Nov 26, 2021

signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT



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@alpha.franken.de>
Cc: Maciej Rozycki <macro@orcam.me.uk>
Cc: linux-mips@vger.kernel.org
[1] 35938a00 ("MIPS: Fix ISA I FP sigcontext access violation handling")
[2] f92722dc ("MIPS: Correct MIPS I FP sigcontext layout")
Cc: stable@vger.kernel.org
Fixes: f92722dc ("MIPS: Correct MIPS I FP sigcontext layout")
Acked-by: Maciej W. Rozycki <macro@orcam.me.uk>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Link: https://lkml.kernel.org/r/20211020174406.17889-5-ebiederm@xmission.com


Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 09cdce82

arch/mips/kernel/r2300_fpu.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -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

arch/mips/kernel/syscall.c

+0 −9

Original line number	Diff line number	Diff line
		@@ -235,12 +235,3 @@ SYSCALL_DEFINE3(cachectl, char *, addr, int, nbytes, int, op)
		{
		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);
		}