linux-kernel - Re: [syzbot] [io-uring?] KASAN: null-ptr-deref Read in io_sqe_buffer

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Message-Id: <20250904202535.fff5bea806408171d349a7f1@linux-foundation.org>
Date: Thu, 4 Sep 2025 20:25:35 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jens Axboe <axboe@...nel.dk>
Cc: syzbot <syzbot+1ab243d3eebb2aabf4a4@...kaller.appspotmail.com>,
 io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com, David Hildenbrand <david@...hat.com>
Subject: Re: [syzbot] [io-uring?] KASAN: null-ptr-deref Read in
 io_sqe_buffer_register

On Thu, 4 Sep 2025 17:20:41 -0600 Jens Axboe <axboe@...nel.dk> wrote:

> > ==================================================================
> 
> This is from the mm-unstable changes in linux-next, adding David as I
> ran a quick bisect and it said:
> 
> da6b34293ff8dbb78f8b9278c9a492925bbf1f87 is the first bad commit
> commit da6b34293ff8dbb78f8b9278c9a492925bbf1f87
> Author: David Hildenbrand <david@...hat.com>
> Date:   Mon Sep 1 17:03:40 2025 +0200
> 
>     mm/gup: remove record_subpages()
>     
>     We can just cleanup the code by calculating the #refs earlier, so we can
>     just inline what remains of record_subpages().
>     
>     Calculate the number of references/pages ahead of times, and record them
>     only once all our tests passed.
>     
>     Link: https://lkml.kernel.org/r/20250901150359.867252-20-david@redhat.com
>     Signed-off-by: David Hildenbrand <david@...hat.com>
>     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> 
> I won't personally have time to look into this until after the weekend,
> but as it's linux-next specific, not a huge deal right now.
> 
> Note that there's also a similar report, which is the same thing:
> 
> https://lore.kernel.org/all/68b9d130.a00a0220.eb3d.0008.GAE@google.com/
> 
> which I marked as dupe of this one.

Thanks.  Seems i can remove that patch without causing merge or build
damage, so I'll do that.