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

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Message-ID: <9ddf41e2-bee6-4b31-a602-53b5485e0f6e@kernel.dk>
Date: Wed, 4 Dec 2024 11:43:30 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Tamir Duberstein <tamird@...il.com>, Matthew Wilcox <willy@...radead.org>
Cc: syzbot <syzbot+092bbab7da235a02a03a@...kaller.appspotmail.com>,
 asml.silence@...il.com, io-uring@...r.kernel.org,
 linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [syzbot] [io-uring?] KASAN: null-ptr-deref Write in
 sys_io_uring_register

On 12/4/24 11:39 AM, Tamir Duberstein wrote:
> On Wed, Dec 4, 2024 at 11:30 AM Tamir Duberstein <tamird@...il.com> wrote:
>>
>> On Wed, Dec 4, 2024 at 11:25 AM Matthew Wilcox <willy@...radead.org> wrote:
>>>
>>> On Wed, Dec 04, 2024 at 09:17:27AM -0700, Jens Axboe wrote:
>>>>>   XA_STATE(xas, xa, index);
>>>>> - return xas_result(&xas, xas_store(&xas, NULL));
>>>>> + return xas_result(&xas, xa_zero_to_null(xas_store(&xas, NULL)));
>>>>>  }
>>>>>  EXPORT_SYMBOL(__xa_erase);
>>>>>
>>>>> This would explain deletion of a reserved entry returning
>>>>> `XA_ZERO_ENTRY` rather than `NULL`.
>>>>
>>>> Yep this works.
>>>>
>>>>> My apologies for this breakage. Should I send a new version? A new
>>>>> "fixes" patch?
>>>>
>>>> Since it seems quite drastically broken, and since it looks like Andrew
>>>> is holding it, seems like the best course of action would be to have it
>>>> folded with the existing patch.
> 
> Is there anything I can do to help with this?

I think Andrew will just fold it in once he sees this thread - but if you
want to be sure, I'd send it out separately with a note below the '---'
line asking him to fold it with the problematic patch.

-- 
Jens Axboe