[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+726f2ce6dbbf2ad8d133@xxxxxxxxxxxxxxxxxxxxxxxxx

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


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches