[syzbot] BUG: unable to handle kernel NULL pointer dereference in kiocb_done

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4ac6d90867a4 Merge tag 'docs-5.15' of git://git.lwn.net/li..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13a275f5300000
kernel config: https://syzkaller.appspot.com/x/.config?x=3c3a5498e99259cf
dashboard link: https://syzkaller.appspot.com/bug?extid=726f2ce6dbbf2ad8d133
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=124a3b49300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=142e610b300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+726f2c...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 26f41067 P4D 26f41067 PUD 17c87067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 8473 Comm: iou-wrk-8424 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900016af910 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888036b6c000
RBP: ffff888036b6c000 R08: 0000000000000000 R09: ffff8880191787d7
R10: ffffffff81e263e4 R11: 0000000000000000 R12: 0000000000000000
R13: ffff888036b6c058 R14: ffff888036b6c040 R15: 0000000000000000
FS: 0000000002442400(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000001d9bc000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
io_rw_done fs/io_uring.c:2905 [inline]
kiocb_done+0x1b3/0x980 fs/io_uring.c:2929
io_read+0x3d3/0x1140 fs/io_uring.c:3503
io_issue_sqe+0x209/0x6ba0 fs/io_uring.c:6558
io_wq_submit_work+0x1d4/0x300 fs/io_uring.c:6707
io_worker_handle_work+0xcb1/0x1950 fs/io-wq.c:560
io_wqe_worker+0x2cc/0xbb0 fs/io-wq.c:609
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Modules linked in:
CR2: 0000000000000000
---[ end trace f60cb53b8a968c33 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900016af910 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888036b6c000
RBP: ffff888036b6c000 R08: 0000000000000000 R09: ffff8880191787d7
R10: ffffffff81e263e4 R11: 0000000000000000 R12: 0000000000000000
R13: ffff888036b6c058 R14: ffff888036b6c040 R15: 0000000000000000
FS: 0000000002442400(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000001d9bc000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Jens Axboe]

On 9/3/21 2:28 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 4ac6d90867a4 Merge tag 'docs-5.15' of git://git.lwn.net/li..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13a275f5300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=3c3a5498e99259cf
> dashboard link: https://syzkaller.appspot.com/bug?extid=726f2ce6dbbf2ad8d133
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=124a3b49300000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=142e610b300000

#syz test git://git.kernel.dk/linux-block for-5.15/io_uring

--
Jens Axboe

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+726f2c...@syzkaller.appspotmail.com

Tested on:

commit: 31efe48e io_uring: fix possible poll event lost in mul..
git tree: git://git.kernel.dk/linux-block for-5.15/io_uring
kernel config: https://syzkaller.appspot.com/x/.config?x=fa8e68781da309a

dashboard link: https://syzkaller.appspot.com/bug?extid=726f2ce6dbbf2ad8d133
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit b8ce1b9d25ccf81e1bbabd45b963ed98b2222df8
Author: Pavel Begunkov <asml.s...@gmail.com>
Date: Tue Aug 31 13:13:11 2021 +0000

io_uring: don't submit half-prepared drain request

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17b14b67300000
start commit: 4ac6d90867a4 Merge tag 'docs-5.15' of git://git.lwn.net/li..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=3c3a5498e99259cf
dashboard link: https://syzkaller.appspot.com/bug?extid=726f2ce6dbbf2ad8d133

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=124a3b49300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=142e610b300000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: io_uring: don't submit half-prepared drain request

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Jens Axboe]

--
Jens Axboe