[syzbot] [fs?] [io-uring?] WARNING: locking bug in eventfd_signal_mask

[syzbot] [fs?] [io-uring?] WARNING: locking bug in eventfd_signal_mask

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9b2ffa6148b1 Merge tag 'mtd/fixes-for-6.13-rc5' of git://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=128f74c4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d269ef41b9262400
dashboard link: https://syzkaller.appspot.com/bug?extid=b1fc199a40b65d601b65
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1469890f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154b22f8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9015cc2b19ac/disk-9b2ffa61.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3ddeabd5e7eb/vmlinux-9b2ffa61.xz
kernel image: https://storage.googleapis.com/syzbot-assets/36e13b0305d0/bzImage-9b2ffa61.xz

The issue was bisected to:

commit 020b40f3562495f3c703a283ece145ffec19e82d
Author: Jens Axboe <axboe@kernel.dk>
Date:   Tue Dec 17 15:21:46 2024 +0000

    io_uring: make ctx->timeout_lock a raw spinlock

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=124d0018580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=114d0018580000
console output: https://syzkaller.appspot.com/x/log.txt?x=164d0018580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b1fc199a40b65d601b65@syzkaller.appspotmail.com
Fixes: 020b40f35624 ("io_uring: make ctx->timeout_lock a raw spinlock")

=============================
[ BUG: Invalid wait context ]
6.13.0-rc4-syzkaller-00012-g9b2ffa6148b1 #0 Not tainted
-----------------------------
kworker/u8:2/35 is trying to lock:
ffff888033f47a20 (&ctx->wqh){....}-{3:3}, at: eventfd_signal_mask+0x7a/0x1f0 fs/eventfd.c:71
other info that might help us debug this:
context-{5:5}
6 locks held by kworker/u8:2/35:
 #0: ffff88801bb04948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801bb04948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3310
 #1: ffffc90000ab7d00 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc90000ab7d00 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3310
 #2: ffff888033bee3d8 (&ctx->completion_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffff888033bee3d8 (&ctx->completion_lock){+.+.}-{3:3}, at: io_kill_timeouts+0x3c/0x230 io_uring/timeout.c:670
 #3: ffff888033bee358 (&ctx->timeout_lock){....}-{2:2}, at: io_kill_timeouts+0x4b/0x230 io_uring/timeout.c:671
 #4: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #4: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #4: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1161 [inline]
 #4: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: io_req_local_work_add+0xb5/0x5c0 io_uring/io_uring.c:1161
 #5: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #5: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #5: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: io_eventfd_grab+0xc2/0x6a0 io_uring/eventfd.c:97
stack backtrace:
CPU: 0 UID: 0 PID: 35 Comm: kworker/u8:2 Not tainted 6.13.0-rc4-syzkaller-00012-g9b2ffa6148b1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: iou_exit io_ring_exit_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_lock_invalid_wait_context kernel/locking/lockdep.c:4826 [inline]
 check_wait_context kernel/locking/lockdep.c:4898 [inline]
 __lock_acquire+0x15a8/0x2100 kernel/locking/lockdep.c:5176
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
 eventfd_signal_mask+0x7a/0x1f0 fs/eventfd.c:71
 __io_eventfd_signal io_uring/eventfd.c:65 [inline]
 io_eventfd_signal+0x96/0x1d0 io_uring/eventfd.c:123
 io_req_local_work_add+0x408/0x5c0 io_uring/io_uring.c:1202
 io_req_task_work_add io_uring/io_uring.h:149 [inline]
 io_req_queue_tw_complete io_uring/io_uring.h:451 [inline]
 io_kill_timeout+0x27b/0x310 io_uring/timeout.c:101
 io_kill_timeouts+0x1b7/0x230 io_uring/timeout.c:676
 io_uring_try_cancel_requests+0x480/0x560 io_uring/io_uring.c:3117
 io_ring_exit_work+0x231/0x8a0 io_uring/io_uring.c:2901
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


---
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Re: [syzbot] [fs?] [io-uring?] WARNING: locking bug in eventfd_signal_mask

[Jens Axboe]

On 12/29/24 2:01 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    9b2ffa6148b1 Merge tag 'mtd/fixes-for-6.13-rc5' of git://g..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=128f74c4580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d269ef41b9262400
> dashboard link: https://syzkaller.appspot.com/bug?extid=b1fc199a40b65d601b65
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1469890f980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154b22f8580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/9015cc2b19ac/disk-9b2ffa61.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/3ddeabd5e7eb/vmlinux-9b2ffa61.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/36e13b0305d0/bzImage-9b2ffa61.xz
> 
> The issue was bisected to:
> 
> commit 020b40f3562495f3c703a283ece145ffec19e82d
> Author: Jens Axboe <axboe@kernel.dk>
> Date:   Tue Dec 17 15:21:46 2024 +0000
> 
>     io_uring: make ctx->timeout_lock a raw spinlock

#syz test: git://git.kernel.dk/linux io_uring-6.13

-- 
Jens Axboe

Re: [syzbot] [fs?] [io-uring?] WARNING: locking bug in eventfd_signal_mask

[syzbot]

Hello,

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

Reported-by: syzbot+b1fc199a40b65d601b65@syzkaller.appspotmail.com
Tested-by: syzbot+b1fc199a40b65d601b65@syzkaller.appspotmail.com

Tested on:

commit:         a9c83a0a io_uring/timeout: flush timeouts outside of t..
git tree:       git://git.kernel.dk/linux io_uring-6.13
console output: https://syzkaller.appspot.com/x/log.txt?x=1566eaf8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=50c7a61469ce77e7
dashboard link: https://syzkaller.appspot.com/bug?extid=b1fc199a40b65d601b65
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.