Subject: Re: [PATCH] mm: shmem: do not call PageHWPoison on a ERR-page
From:   Jens Axboe <axboe@kernel.dk>
To:     Ajay Garg <ajaygargnsit@gmail.com>, hughd@google.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>
References: <20211111084617.6746-1-ajaygargnsit@gmail.com>
 <CAHP4M8V2WEQ0LgHp7PHdBMYFp+_frn=7GLQVF7=faqapojQ+2g@mail.gmail.com>
 <628a49dc-f6f7-5aa4-8a4d-4f2ed19b7f3f@kernel.dk>
Message-ID: <e87601bd-21c4-00b0-9500-054bca8abced@kernel.dk>
Date:   Sat, 13 Nov 2021 10:21:15 -0700
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On 11/11/21 10:59 AM, Jens Axboe wrote:
> On 11/11/21 10:45 AM, Ajay Garg wrote:
>> Another report of the issue (different call-flow, but the same error
>> at "shmem_read_mapping_page_gfp") at :
>> https://lore.kernel.org/lkml/6bb8c25c-cdcf-8bca-3db2-9871a90d518f@kernel.dk/T/#m52d98b6bdb05764524a118b15cec048b34e5ca76
>>
>> with a tentative approval for the patch :
>> https://lore.kernel.org/lkml/6bb8c25c-cdcf-8bca-3db2-9871a90d518f@kernel.dk/T/#m24c2888a879d428cde5b34c43838301de544eb7e
> 
> Andrew, I've hit this multiple times on resume on my laptop, and it's
> a very apparent bug in that b9d02f1bdd98 commit that it doesn't factor
> in error pointers. My oops clearly shows it being one too, with ...fff4
> being the dereference address.
> 
> Can we get this pushed upstream asap if you're fine with this patch?

Maybe Andrew is out - Linus, if you follow this thread, there are two
proposed fixes for this. It'd be nice to have one of them in -rc1.

Backstory is that commit:

commit b9d02f1bdd98f38e6e5ecacc9786a8f58f3f8b2c
Author: Yang Shi <shy828301@gmail.com>
Date:   Fri Nov 5 13:41:10 2021 -0700

    mm: shmem: don't truncate page if memory failure happens

adds a pretty obvious error, where PageHWPoison() is called on an error
pointer in shmem_read_mapping_page_gfp(). I can trivially hit this oops
on resuming the laptop.

-- 
Jens Axboe