linux-kernel - Re: [REVIEW][PATCH 03/26] signal/arm64: Use force_sig not force_sig

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Date:   Thu, 23 May 2019 11:17:02 +0100
From:   Will Deacon <will.deacon@....com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>, linux-arch@...r.kernel.org,
        Dave Martin <Dave.Martin@....com>,
        James Morse <james.morse@....com>
Subject: Re: [REVIEW][PATCH 03/26] signal/arm64: Use force_sig not
 force_sig_fault for SIGKILL

On Wed, May 22, 2019 at 07:38:53PM -0500, Eric W. Biederman wrote:
> It really only matters to debuggers but the SIGKILL does not have any
> si_codes that use the fault member of the siginfo union.  Correct this
> the simple way and call force_sig instead of force_sig_fault when the
> signal is SIGKILL.
> 
> Cc: stable@...r.kernel.org
> Cc: Dave Martin <Dave.Martin@....com>
> Cc: James Morse <james.morse@....com>
> Cc: Will Deacon <will.deacon@....com>
> Fixes: af40ff687bc9 ("arm64: signal: Ensure si_code is valid for all fault signals")
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---
>  arch/arm64/kernel/traps.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index ade32046f3fe..0feb17bdcaa0 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -282,6 +282,11 @@ void arm64_notify_die(const char *str, struct pt_regs *regs,
>  		current->thread.fault_address = 0;
>  		current->thread.fault_code = err;
>  
> +		if (signo == SIGKILL) {
> +			arm64_show_signal(signo, str);
> +			force_sig(signo, current);
> +			return;
> +		}

I know it's a bit of a misnomer, but I'd rather do this check inside
arm64_force_sig_fault, since I think we have other callers (e.g.
do_bad_area()) which also blindly pass in SIGKILL here.

We could rename the thing if necessary.

Will