[syzbot] [block?] possible deadlock in elv_iosched_store

From: syzbot
Date: Fri Mar 28 2025 - 10:38:19 EST

Next message: syzbot: "[syzbot] [nilfs?] possible deadlock in nilfs_evict_inode (3)"
Previous message: Krzysztof Kozlowski: "Re: [PATCH v2 2/3] i3c: master: Add Qualcomm I3C controller driver"
Next in thread: Ming Lei: "Re: [syzbot] [block?] possible deadlock in elv_iosched_store"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hello,

syzbot found the following issue on:

HEAD commit: 1a9239bb4253 Merge tag 'net-next-6.15' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1384b43f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c7163a109ac459a8
dashboard link: https://syzkaller.appspot.com/bug?extid=4c7e0f9b94ad65811efb
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=178cfa4c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11a8ca4c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fc7dc9f0d9a7/disk-1a9239bb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f555a3ae03d3/vmlinux-1a9239bb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/55f6ea74eaf2/bzImage-1a9239bb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c7e0f9b94ad65811efb@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.14.0-syzkaller-05877-g1a9239bb4253 #0 Not tainted
------------------------------------------------------
syz-executor192/5823 is trying to acquire lock:
ffff888144302cd8 (&q->elevator_lock){+.+.}-{4:4}, at: elv_iosched_store+0x201/0x5f0 block/elevator.c:735

but task is already holding lock:
ffff8881443027a8 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&q->q_usage_counter(io)#58){++++}-{0:0}:
blk_alloc_queue+0x619/0x760 block/blk-core.c:461
blk_mq_alloc_queue+0x179/0x290 block/blk-mq.c:4349
__blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4396
nbd_dev_add+0x49d/0xbb0 drivers/block/nbd.c:1933
nbd_init+0x181/0x320 drivers/block/nbd.c:2670
do_one_initcall+0x120/0x6e0 init/main.c:1257
do_initcall_level init/main.c:1319 [inline]
do_initcalls init/main.c:1335 [inline]
do_basic_setup init/main.c:1354 [inline]
kernel_init_freeable+0x5c2/0x900 init/main.c:1567
kernel_init+0x1c/0x2b0 init/main.c:1457
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (fs_reclaim){+.+.}-{0:0}:
__fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:3867
might_alloc include/linux/sched/mm.h:318 [inline]
xa_insert include/linux/xarray.h:783 [inline]
blk_mq_init_hctx block/blk-mq.c:3924 [inline]
blk_mq_alloc_and_init_hctx+0x503/0x11c0 block/blk-mq.c:4457
blk_mq_realloc_hw_ctxs+0x8f6/0xc00 block/blk-mq.c:4486
blk_mq_init_allocated_queue+0x3af/0x1230 block/blk-mq.c:4540
blk_mq_alloc_queue+0x1c2/0x290 block/blk-mq.c:4353
__blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4396
loop_add+0x496/0xb70 drivers/block/loop.c:2067
loop_init+0x164/0x270 drivers/block/loop.c:2302
do_one_initcall+0x120/0x6e0 init/main.c:1257
do_initcall_level init/main.c:1319 [inline]
do_initcalls init/main.c:1335 [inline]
do_basic_setup init/main.c:1354 [inline]
kernel_init_freeable+0x5c2/0x900 init/main.c:1567
kernel_init+0x1c/0x2b0 init/main.c:1457
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (&q->elevator_lock){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3166 [inline]
check_prevs_add kernel/locking/lockdep.c:3285 [inline]
validate_chain kernel/locking/lockdep.c:3909 [inline]
__lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
lock_acquire kernel/locking/lockdep.c:5866 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
__mutex_lock_common kernel/locking/mutex.c:587 [inline]
__mutex_lock+0x19a/0xb00 kernel/locking/mutex.c:732
elv_iosched_store+0x201/0x5f0 block/elevator.c:735
queue_attr_store+0x270/0x310 block/blk-sysfs.c:799
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139
kernfs_fop_write_iter+0x349/0x510 fs/kernfs/file.c:334
iter_file_splice_write+0x91c/0x1150 fs/splice.c:738
do_splice_from fs/splice.c:935 [inline]
direct_splice_actor+0x18f/0x6c0 fs/splice.c:1158
splice_direct_to_actor+0x342/0xa30 fs/splice.c:1102
do_splice_direct_actor fs/splice.c:1201 [inline]
do_splice_direct+0x174/0x240 fs/splice.c:1227
do_sendfile+0xafd/0xe50 fs/read_write.c:1368
__do_sys_sendfile64 fs/read_write.c:1429 [inline]
__se_sys_sendfile64 fs/read_write.c:1415 [inline]
__x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1415
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x260 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:
&q->elevator_lock --> fs_reclaim --> &q->q_usage_counter(io)#58

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&q->q_usage_counter(io)#58);
lock(fs_reclaim);
lock(&q->q_usage_counter(io)#58);
lock(&q->elevator_lock);

*** DEADLOCK ***

5 locks held by syz-executor192/5823:
#0: ffff888035bd2420 (sb_writers#7){.+.+}-{0:0}, at: splice_direct_to_actor+0x342/0xa30 fs/splice.c:1102
#1: ffff888033e17088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x287/0x510 fs/kernfs/file.c:325
#2: ffff8880258933c8 (kn->active#47){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2aa/0x510 fs/kernfs/file.c:326
#3: ffff8881443027a8 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215
#4: ffff8881443027e0 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215

stack backtrace:
CPU: 0 UID: 0 PID: 5823 Comm: syz-executor192 Not tainted 6.14.0-syzkaller-05877-g1a9239bb4253 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079
check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2211
check_prev_add kernel/locking/lockdep.c:3166 [inline]
check_prevs_add kernel/locking/lockdep.c:3285 [inline]
validate_chain kernel/locking/lockdep.c:3909 [inline]
__lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
lock_acquire kernel/locking/lockdep.c:5866 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
__mutex_lock_common kernel/locking/mutex.c:587 [inline]
__mutex_lock+0x19a/0xb00 kernel/locking/mutex.c:732
elv_iosched_store+0x201/0x5f0 block/elevator.c:735
queue_attr_store+0x270/0x310 block/blk-sysfs.c:799
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139
kernfs_fop_write_iter+0x349/0x510 fs/kernfs/file.c:334
iter_file_splice_write+0x91c/0x1150 fs/splice.c:738
do_splice_from fs/splice.c:935 [inline]
direct_splice_actor+0x18f/0x6c0 fs/splice.c:1158
splice_direct_to_actor+0x342/0xa30 fs/splice.c:1102
do_splice_direct_actor fs/splice.c:1201 [inline]
do_splice_direct+0x174/0x240 fs/splice.c:1227
do_sendfile+0xafd/0xe50 fs/read_write.c:1368
__do_sys_sendfile64 fs/read_write.c:1429 [inline]
__se_sys_sendfile64 fs/read_write.c:1415 [inline]
__x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1415
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff2c3abb2e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffc4e88b88 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fffc4e88d58 RCX: 00007ff2c3abb2e9
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000003
RBP: 00007ff2c3b2e610 R08: 0000000000000000 R09: 00007fffc4e88d58
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fffc4e88d48 R14: 0000000000000001 R15: 0000

---
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.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

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

Next message: syzbot: "[syzbot] [nilfs?] possible deadlock in nilfs_evict_inode (3)"
Previous message: Krzysztof Kozlowski: "Re: [PATCH v2 2/3] i3c: master: Add Qualcomm I3C controller driver"
Next in thread: Ming Lei: "Re: [syzbot] [block?] possible deadlock in elv_iosched_store"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]