linux-kernel - Re: [PATCH v2] x86/fault: Send a SIGBUS to user process always for hwpoison page access.

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Message-ID: <CALCETrWrj0LJaHTdrydH-i_OkjDb1VF76aJrAWpHA5PL2npezg@mail.gmail.com>
Date:   Mon, 1 Feb 2021 08:58:27 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Aili Yao <yaoaili@...gsoft.com>
Cc:     Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        naoya.horiguchi@....com, "H. Peter Anvin" <hpa@...or.com>,
        X86 ML <x86@...nel.org>, YANGFENG1@...gsoft.com,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/fault: Send a SIGBUS to user process always for
 hwpoison page access.

On Mon, Feb 1, 2021 at 12:17 AM Aili Yao <yaoaili@...gsoft.com> wrote:
>
> When one page is already hwpoisoned by AO action, process may not be
> killed, the process mapping this page may make a syscall include this
> page and result to trigger a VM_FAULT_HWPOISON fault, if it's in kernel
> mode it may be fixed by fixup_exception. Current code will just return
> error code to user process.
>
> This is not sufficient, we should send a SIGBUS to the process and log
> the info to console, as we can't trust the process will handle the error
> correctly.

Does this happen when one process gets SIGBUSed due to memory failure
and another process independently hits the poisoned memory?  I'm not
entirely convinced that this is a problem.

In any case, this patch needs rebasing on top of my big fault series
-- as it stands, it's way too difficult to keep track of which paths
even call your new code..  And the various signal paths need to be
consolidated -- we already have three of them, and the last thing we
need is a fourth.