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Date:   Sun, 24 Oct 2021 17:27:45 +0200
From:   Thomas Bogendoerfer <>
To:     "Eric W. Biederman" <>
        Linus Torvalds <>,
        Oleg Nesterov <>,
        Al Viro <>,
        Kees Cook <>,
        Maciej Rozycki <>,
Subject: Re: [PATCH 05/20] signal/mips: Update (_save|_restore)_fp_context to
 fail with -EFAULT

On Wed, Oct 20, 2021 at 12:43:51PM -0500, Eric W. Biederman wrote:
> 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")
> Fixes: f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout")
> Signed-off-by: "Eric W. Biederman" <>
> ---
>  arch/mips/kernel/r2300_fpu.S | 4 ++--
>  arch/mips/kernel/syscall.c   | 9 ---------
>  2 files changed, 2 insertions(+), 11 deletions(-)

Acked-by: Thomas Bogendoerfer <>

Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

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