[syzbot] [block?] possible deadlock in __del_gendisk

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3be1a7a31fbd Add linux-next specific files for 20250526
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1573bad4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ab703e8a19430df
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/33e6b012d232/disk-3be1a7a3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f92328298470/vmlinux-3be1a7a3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e5cbdb6f4a5c/bzImage-3be1a7a3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2e9e52...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc7-next-20250526-syzkaller #0 Not tainted
------------------------------------------------------
syz.4.1558/11720 is trying to acquire lock:
ffff888142bb3358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x129/0x9e0 block/genhd.c:706

but task is already holding lock:
ffff888142bb2368 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&set->update_nr_hwq_lock){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
blk_mq_update_nr_hw_queues+0x3b/0x14c0 block/blk-mq.c:5041
nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476
nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2201
genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:727
____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&nbd->config_lock){+.+.}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:602 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
refcount_dec_and_mutex_lock+0x30/0xa0 lib/refcount.c:118
nbd_config_put+0x2c/0x790 drivers/block/nbd.c:1423
nbd_release+0xfe/0x140 drivers/block/nbd.c:1735
bdev_release+0x536/0x650 block/bdev.c:-1
blkdev_release+0x15/0x20 block/fops.c:684
__fput+0x44c/0xa70 fs/file_table.c:467
fput_close_sync+0x119/0x200 fs/file_table.c:572
__do_sys_close fs/open.c:1589 [inline]
__se_sys_close fs/open.c:1574 [inline]
__x64_sys_close+0x7f/0x110 fs/open.c:1574
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&disk->open_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:602 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819
loop_remove+0x42/0xc0 drivers/block/loop.c:2081
loop_control_remove drivers/block/loop.c:2140 [inline]
loop_control_ioctl+0x4a6/0x590 drivers/block/loop.c:2178
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
&disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(&set->update_nr_hwq_lock);
lock(&nbd->config_lock);
lock(&set->update_nr_hwq_lock);
lock(&disk->open_mutex);

*** DEADLOCK ***

1 lock held by syz.4.1558/11720:
#0: ffff888142bb2368 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

stack backtrace:
CPU: 0 UID: 0 PID: 11720 Comm: syz.4.1558 Not tainted 6.15.0-rc7-next-20250526-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:602 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819
loop_remove+0x42/0xc0 drivers/block/loop.c:2081
loop_control_remove drivers/block/loop.c:2140 [inline]
loop_control_ioctl+0x4a6/0x590 drivers/block/loop.c:2178
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f301358e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f30113f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f30137b5fa0 RCX: 00007f301358e969
RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000003
RBP: 00007f3013610ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f30137b5fa0 R15: 00007fffe9613fd8
</TASK>


---
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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: ddddf9d64f73 Merge tag 'perf-core-2025-05-25' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12f87882580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fd18a1001092f95b

dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11825df4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fb7ad4580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ddddf9d6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bc551d1d4e46/vmlinux-ddddf9d6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d26a6de23b0e/bzImage-ddddf9d6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2e9e52...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected

6.15.0-syzkaller-01599-gddddf9d64f73 #0 Not tainted
------------------------------------------------------
kworker/u4:9/1091 is trying to acquire lock:
ffff888011362358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x129/0x9e0 block/genhd.c:706

but task is already holding lock:

ffff88801bb55188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&set->update_nr_hwq_lock){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
blk_mq_update_nr_hw_queues+0x3b/0x14c0 block/blk-mq.c:5041
nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476
nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2201
genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210

netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534

genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]

__sock_sendmsg+0x219/0x270 net/socket.c:727

____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94

entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&nbd->config_lock){+.+.}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871

__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746

refcount_dec_and_mutex_lock+0x30/0xa0 lib/refcount.c:118
nbd_config_put+0x2c/0x790 drivers/block/nbd.c:1423
nbd_release+0xfe/0x140 drivers/block/nbd.c:1735

bdev_release+0x533/0x650 block/bdev.c:-1
blkdev_release+0x15/0x20 block/fops.c:684
__fput+0x449/0xa70 fs/file_table.c:465
fput_close_sync+0x119/0x200 fs/file_table.c:570

__do_sys_close fs/open.c:1589 [inline]
__se_sys_close fs/open.c:1574 [inline]
__x64_sys_close+0x7f/0x110 fs/open.c:1574
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94

entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&disk->open_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871

__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746

__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819

nbd_dev_remove drivers/block/nbd.c:268 [inline]
nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xadb/0x17a0 kernel/workqueue.c:3319
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
kthread+0x711/0x8a0 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
&disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(&set->update_nr_hwq_lock);
lock(&nbd->config_lock);
lock(&set->update_nr_hwq_lock);
lock(&disk->open_mutex);

*** DEADLOCK ***

3 locks held by kworker/u4:9/1091:
#0: ffff88801f317148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
#0: ffff88801f317148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_scheduled_works+0x9b1/0x17a0 kernel/workqueue.c:3319
#1: ffffc90002647c60 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
#1: ffffc90002647c60 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ec/0x17a0 kernel/workqueue.c:3319
#2: ffff88801bb55188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

stack backtrace:
CPU: 0 UID: 0 PID: 1091 Comm: kworker/u4:9 Not tainted 6.15.0-syzkaller-01599-gddddf9d64f73 #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: nbd-del nbd_dev_remove_work

Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871

__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746

__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819

nbd_dev_remove drivers/block/nbd.c:268 [inline]
nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xadb/0x17a0 kernel/workqueue.c:3319
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
kthread+0x711/0x8a0 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[Hillf Danton]

> Date: Mon, 26 May 2025 20:12:27 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: ddddf9d64f73 Merge tag 'perf-core-2025-05-25' of git://git..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12f87882580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=fd18a1001092f95b
> dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
> compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11825df4580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fb7ad4580000

#syz test

--- x/block/bdev.c
+++ y/block/bdev.c
@@ -1137,12 +1137,12 @@ void bdev_release(struct file *bdev_file
* from userland - e.g. eject(1).
*/
disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
+ mutex_unlock(&disk->open_mutex);

if (bdev_is_partition(bdev))
blkdev_put_part(bdev);
else
blkdev_put_whole(bdev);
- mutex_unlock(&disk->open_mutex);

module_put(disk->fops->owner);
put_no_open:
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __del_gendisk

======================================================
WARNING: possible circular locking dependency detected

6.15.0-syzkaller-g914873bc7df9-dirty #0 Not tainted
------------------------------------------------------
kworker/u4:1/13 is trying to acquire lock:
ffff888059e20358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x129/0x9e0 block/genhd.c:706

but task is already holding lock:

ffff888053877188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&set->update_nr_hwq_lock){++++}-{4:4}:

lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
blk_mq_update_nr_hw_queues+0x3b/0x14c0 block/blk-mq.c:5041
nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476
nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2201

genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115

genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210

netlink_rcv_skb+0x21c/0x490 net/netlink/af_netlink.c:2534

genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]

netlink_unicast+0x758/0x8d0 net/netlink/af_netlink.c:1339

netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]

__sock_sendmsg+0x21c/0x270 net/socket.c:727

____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

do_syscall_64+0xf6/0x220 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&nbd->config_lock){+.+.}-{4:4}:

lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746

nbd_open+0x2b7/0x5d0 drivers/block/nbd.c:1703
blkdev_get_whole+0x98/0x510 block/bdev.c:730
bdev_open+0x31e/0xd30 block/bdev.c:957
blkdev_open+0x3a8/0x510 block/fops.c:676
do_dentry_open+0xdf3/0x1970 fs/open.c:964
vfs_open+0x3b/0x340 fs/open.c:1094
do_open fs/namei.c:3887 [inline]
path_openat+0x2ee5/0x3830 fs/namei.c:4046
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf6/0x220 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (nbd_index_mutex){+.+.}-{4:4}:

lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746

nbd_open+0x7b/0x5d0 drivers/block/nbd.c:1690
blkdev_get_whole+0x98/0x510 block/bdev.c:730
bdev_open+0x31e/0xd30 block/bdev.c:957
blkdev_open+0x3a8/0x510 block/fops.c:676
do_dentry_open+0xdf3/0x1970 fs/open.c:964
vfs_open+0x3b/0x340 fs/open.c:1094
do_open fs/namei.c:3887 [inline]
path_openat+0x2ee5/0x3830 fs/namei.c:4046
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf6/0x220 arch/x86/entry/syscall_64.c:94

entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&disk->open_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819
nbd_dev_remove drivers/block/nbd.c:268 [inline]
nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284
process_one_work kernel/workqueue.c:3238 [inline]

process_scheduled_works+0xade/0x17a0 kernel/workqueue.c:3319
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x4e/0x80 arch/x86/kernel/process.c:148

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
&disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(&set->update_nr_hwq_lock);
lock(&nbd->config_lock);
lock(&set->update_nr_hwq_lock);
lock(&disk->open_mutex);

*** DEADLOCK ***

3 locks held by kworker/u4:1/13:
#0: ffff888000b13148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
#0: ffff888000b13148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_scheduled_works+0x9b1/0x17a0 kernel/workqueue.c:3319
#1: ffffc900001f7c60 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
#1: ffffc900001f7c60 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ec/0x17a0 kernel/workqueue.c:3319
#2: ffff888053877188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

stack backtrace:
CPU: 0 UID: 0 PID: 13 Comm: kworker/u4:1 Not tainted 6.15.0-syzkaller-g914873bc7df9-dirty #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: nbd-del nbd_dev_remove_work
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819
nbd_dev_remove drivers/block/nbd.c:268 [inline]
nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284
process_one_work kernel/workqueue.c:3238 [inline]

process_scheduled_works+0xade/0x17a0 kernel/workqueue.c:3319
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x4e/0x80 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50


Tested on:

commit: 914873bc Merge tag 'x86-build-2025-05-25' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=141fbdf4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=eeb82b5d1d67d535

dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

patch: https://syzkaller.appspot.com/x/patch.diff?x=13f7bdf4580000

[Hillf Danton]

> Date: Mon, 26 May 2025 20:12:27 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: ddddf9d64f73 Merge tag 'perf-core-2025-05-25' of git://git..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12f87882580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=fd18a1001092f95b
> dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
> compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11825df4580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fb7ad4580000

#syz test

--- x/block/bdev.c
+++ y/block/bdev.c
@@ -1137,12 +1137,12 @@ void bdev_release(struct file *bdev_file
* from userland - e.g. eject(1).
*/
disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
+ mutex_unlock(&disk->open_mutex);

if (bdev_is_partition(bdev))
blkdev_put_part(bdev);
else
blkdev_put_whole(bdev);
- mutex_unlock(&disk->open_mutex);

module_put(disk->fops->owner);
put_no_open:

--- l/drivers/block/nbd.c
+++ y/drivers/block/nbd.c
@@ -1700,21 +1700,23 @@ static int nbd_open(struct gendisk *disk

config = nbd_get_config_unlocked(nbd);
if (!config) {
+ mutex_unlock(&nbd_index_mutex);
mutex_lock(&nbd->config_lock);
if (refcount_inc_not_zero(&nbd->config_refs)) {
mutex_unlock(&nbd->config_lock);
- goto out;
+ retuen 0;
}
ret = nbd_alloc_and_init_config(nbd);
if (ret) {
mutex_unlock(&nbd->config_lock);
- goto out;
+ retuen ret;
}

refcount_inc(&nbd->refs);
mutex_unlock(&nbd->config_lock);
if (max_part)
set_bit(GD_NEED_PART_SCAN, &disk->state);
+ retuen 0;
} else if (nbd_disconnected(config)) {
if (max_part)
set_bit(GD_NEED_PART_SCAN, &disk->state);
--

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

drivers/block/nbd.c:1707:4: error: use of undeclared identifier 'retuen'
drivers/block/nbd.c:1712:4: error: use of undeclared identifier 'retuen'; did you mean 'return'?
drivers/block/nbd.c:1719:3: error: use of undeclared identifier 'retuen'


Tested on:

commit: feacb177 Merge tag 'sched_ext-for-6.16' of git://git.k..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=fd18a1001092f95b
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

patch: https://syzkaller.appspot.com/x/patch.diff?x=11e70bf4580000

[Hillf Danton]

> Date: Mon, 26 May 2025 20:12:27 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: ddddf9d64f73 Merge tag 'perf-core-2025-05-25' of git://git..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12f87882580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=fd18a1001092f95b
> dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
> compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11825df4580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fb7ad4580000

+ return 0;

}
ret = nbd_alloc_and_init_config(nbd);
if (ret) {
mutex_unlock(&nbd->config_lock);
- goto out;

+ return ret;

}

refcount_inc(&nbd->refs);
mutex_unlock(&nbd->config_lock);
if (max_part)
set_bit(GD_NEED_PART_SCAN, &disk->state);

+ return 0;

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __del_gendisk

======================================================
WARNING: possible circular locking dependency detected

6.15.0-syzkaller-g90b83efa6701-dirty #0 Not tainted
------------------------------------------------------
kworker/u4:2/31 is trying to acquire lock:
ffff888000617358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x129/0x9e0 block/genhd.c:706

but task is already holding lock:

ffff88803f055188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&set->update_nr_hwq_lock){++++}-{4:4}:

lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
blk_mq_update_nr_hw_queues+0x3b/0x14c0 block/blk-mq.c:5041
nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476

nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2203
genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115

genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210

netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534

genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]

netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339

netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:727
____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&nbd->config_lock){+.+.}-{4:4}:

lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746

nbd_open+0x2c3/0x5f0 drivers/block/nbd.c:1704

blkdev_get_whole+0x98/0x510 block/bdev.c:730
bdev_open+0x31e/0xd30 block/bdev.c:957
blkdev_open+0x3a8/0x510 block/fops.c:676

do_dentry_open+0xdf0/0x1970 fs/open.c:964

vfs_open+0x3b/0x340 fs/open.c:1094
do_open fs/namei.c:3887 [inline]
path_openat+0x2ee5/0x3830 fs/namei.c:4046
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94

entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&disk->open_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819
nbd_dev_remove drivers/block/nbd.c:268 [inline]
nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284
process_one_work kernel/workqueue.c:3238 [inline]

process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
&disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(&set->update_nr_hwq_lock);
lock(&nbd->config_lock);
lock(&set->update_nr_hwq_lock);
lock(&disk->open_mutex);

*** DEADLOCK ***

3 locks held by kworker/u4:2/31:
#0: ffff88801f97e148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
#0: ffff88801f97e148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3321
#1: ffffc90000527bc0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
#1: ffffc90000527bc0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3321
#2: ffff88803f055188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818

stack backtrace:
CPU: 0 UID: 0 PID: 31 Comm: kworker/u4:2 Not tainted 6.15.0-syzkaller-g90b83efa6701-dirty #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: nbd-del nbd_dev_remove_work
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
__del_gendisk+0x129/0x9e0 block/genhd.c:706
del_gendisk+0xe8/0x160 block/genhd.c:819
nbd_dev_remove drivers/block/nbd.c:268 [inline]
nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284
process_one_work kernel/workqueue.c:3238 [inline]

process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


Tested on:

commit: 90b83efa Merge tag 'bpf-next-6.16' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16892482580000
kernel config: https://syzkaller.appspot.com/x/.config?x=262b2977ef00756b

dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

patch: https://syzkaller.appspot.com/x/patch.diff?x=1345dbf4580000

[syzbot]

syzbot has bisected this issue to:

commit f1be1788a32e8fa63416ad4518bbd1a85a825c9d
Author: Ming Lei <ming...@redhat.com>
Date: Fri Oct 25 00:37:20 2024 +0000

block: model freeze & enter queue as lock for supporting lockdep

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1024db0c580000
start commit: e0fca6f2cebf net: mana: Record doorbell physical address i..
git tree: net
final oops: https://syzkaller.appspot.com/x/report.txt?x=1224db0c580000
console output: https://syzkaller.appspot.com/x/log.txt?x=1424db0c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d11f52d3049c3790
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9e529ac0b319316453
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=132f8dd4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14aac182580000

Reported-by: syzbot+2e9e52...@syzkaller.appspotmail.com
Fixes: f1be1788a32e ("block: model freeze & enter queue as lock for supporting lockdep")

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

[Ming Lei]

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7bdc7eb808ea..aa249719fa7f 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1473,7 +1473,12 @@ static int nbd_start_device(struct nbd_device *nbd)
return -EINVAL;
}

- blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections);
+ mutex_unlock(&nbd->config_lock);
+ blk_mq_update_nr_hw_queues(&nbd->tag_set, num_connections);
+ mutex_lock(&nbd->config_lock);
+ if (config->num_connections != num_connections)
+ return -EINVAL;
+
nbd->pid = task_pid_nr(current);

nbd_parse_flags(nbd);

Thanks,
Ming

[syzbot]

For archival purposes, forwarding an incoming command email to
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***

Subject: Fix reported __del_gendisk deadlock
Author: ujwal....@gmail.com

#syz test

diff --git a/block/genhd.c b/block/genhd.c
index c26733f6324b..bad731186189 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -819,9 +819,11 @@ void del_gendisk(struct gendisk *disk)
disable_elv_switch(disk->queue);

memflags = memalloc_noio_save();
+ mutex_lock(&set->tag_list_lock);
down_read(&set->update_nr_hwq_lock);
__del_gendisk(disk);
up_read(&set->update_nr_hwq_lock);
+ mutex_unlock(&set->tag_list_lock);
memalloc_noio_restore(memflags);
}
}

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***

Subject: Re: Fix reported __del_gendisk deadlock

Author: ujwal....@gmail.com

#syz test

diff --git a/block/genhd.c b/block/genhd.c
index c26733f6324b..bad731186189 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -819,9 +819,11 @@ void del_gendisk(struct gendisk *disk)
disable_elv_switch(disk->queue);

memflags = memalloc_noio_save();
+ mutex_lock(&set->tag_list_lock);
down_read(&set->update_nr_hwq_lock);
__del_gendisk(disk);
up_read(&set->update_nr_hwq_lock);
+ mutex_unlock(&set->tag_list_lock);
memalloc_noio_restore(memflags);
}
}

--
2.30.2

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Subject: Re: [syzbot] [block?] possible deadlock in __del_gendisk
Author: ujwal....@gmail.com

#syz test

[syzbot]

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***

Subject: Fix unsafe locking scenario in del_gendisk
Author: ujwal....@gmail.com

#syz test

[syzbot]

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[syzbot]