linux-kernel - Re: [PATCH] signal/x86: Don't send SIGSEGV twice on SEGV

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Date:   Thu, 3 Jun 2021 20:37:11 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jiashuo Liang <liangjs@....edu.cn>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] signal/x86: Don't send SIGSEGV twice on SEGV_PKUERR

On Tue, Jun 01, 2021 at 04:52:03PM +0800, Jiashuo Liang wrote:
> Before this patch, the __bad_area_nosemaphore function calls both
> force_sig_pkuerr and force_sig_fault when handling SEGV_PKUERR. This does
> not cause problems because the second signal is filtered by the
> legacy_queue check in __send_signal.

I'm likely missing something but the first signal gets filtered by that
same legacy_queue() check too, no?

Because both calls end up in

	force_sig_info_to_task(info, current);

with the info struct populated with:

	info.si_signo = SIGSEGV;
        info.si_errno = 0;
        info.si_code  = SEGV_PKUERR;
        info.si_addr  = addr;
        info.si_pkey  = pkey;

except the second call - force_sig_fault() - doesn't put pkey in
->si_pkey.

So what's up?

Thx.

-- 
Regards/Gruss,
    Boris.

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