* [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2)
@ 2025-08-29 18:38 syzbot
2025-08-30 0:06 ` syzbot
2025-08-30 0:45 ` Hillf Danton
0 siblings, 2 replies; 6+ messages in thread
From: syzbot @ 2025-08-29 18:38 UTC (permalink / raw)
To: linux-kernel, linux-sound, perex, syzkaller-bugs, tiwai
Hello,
syzbot found the following issue on:
HEAD commit: 07d9df80082b Merge tag 'perf-tools-fixes-for-v6.17-2025-08..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17333fbc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
dashboard link: https://syzkaller.appspot.com/bug?extid=10b4363fb0f46527f3f3
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=160e9262580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17ed0242580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cdf0bbb7922b/disk-07d9df80.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d1975bf771ed/vmlinux-07d9df80.xz
kernel image: https://storage.googleapis.com/syzbot-assets/942416e1bedd/bzImage-07d9df80.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+10b4363fb0f46527f3f3@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.48/6160 is trying to acquire lock:
ffff8880b8923d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
ffff8880b8923d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168
but task is already holding lock:
ffff88802f930150 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&group->lock#2){+.+.}-{3:3}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56
spin_lock include/linux/spinlock_rt.h:44 [inline]
_snd_pcm_stream_lock_irqsave+0x7c/0xa0 sound/core/pcm_native.c:171
class_pcm_stream_lock_irqsave_constructor include/sound/pcm.h:682 [inline]
snd_pcm_period_elapsed+0x1e/0x80 sound/core/pcm_lib.c:1938
dummy_hrtimer_callback+0x80/0x180 sound/drivers/dummy.c:386
__run_hrtimer kernel/time/hrtimer.c:1761 [inline]
__hrtimer_run_queues+0x54f/0xd40 kernel/time/hrtimer.c:1825
hrtimer_run_softirq+0x1a3/0x2e0 kernel/time/hrtimer.c:1842
handle_softirqs+0x22c/0x710 kernel/softirq.c:579
__do_softirq kernel/softirq.c:613 [inline]
run_ktimerd+0xcf/0x190 kernel/softirq.c:1043
smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #1 (&base->softirq_expiry_lock){+...}-{3:3}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56
spin_lock include/linux/spinlock_rt.h:44 [inline]
hrtimer_cpu_base_lock_expiry kernel/time/hrtimer.c:1383 [inline]
hrtimer_run_softirq+0x7c/0x2e0 kernel/time/hrtimer.c:1838
handle_softirqs+0x22c/0x710 kernel/softirq.c:579
__do_softirq kernel/softirq.c:613 [inline]
run_ktimerd+0xcf/0x190 kernel/softirq.c:1043
smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #0 ((softirq_ctrl.lock)){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385
__lock_release kernel/locking/lockdep.c:5574 [inline]
lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889
__local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228
hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491
dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410
snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525
snd_pcm_action_single sound/core/pcm_native.c:1305 [inline]
snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388
__snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180
snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224
snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493
snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline]
__snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326
snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241
snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795
vfs_write+0x284/0xb40 fs/read_write.c:684
ksys_write+0x14b/0x260 fs/read_write.c:738
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:
(softirq_ctrl.lock) --> &base->softirq_expiry_lock --> &group->lock#2
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&group->lock#2);
lock(&base->softirq_expiry_lock);
lock(&group->lock#2);
lock((softirq_ctrl.lock));
*** DEADLOCK ***
2 locks held by syz.0.48/6160:
#0: ffff88802f930150 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1bb/0x2c0 kernel/locking/spinlock_rt.c:57
stack backtrace:
CPU: 1 UID: 0 PID: 6160 Comm: syz.0.48 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385
__lock_release kernel/locking/lockdep.c:5574 [inline]
lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889
__local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228
hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491
dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410
snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525
snd_pcm_action_single sound/core/pcm_native.c:1305 [inline]
snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388
__snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180
snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224
snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493
snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline]
__snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326
snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241
snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795
vfs_write+0x284/0xb40 fs/read_write.c:684
ksys_write+0x14b/0x260 fs/read_write.c:738
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: 0033:0x7f0e7a70ebe9
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:00007ffe73a3cd48 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f0e7a935fa0 RCX: 00007f0e7a70ebe9
RDX: 000000000000fc36 RSI: 0000200000000500 RDI: 0000000000000003
RBP: 00007f0e7a791e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0e7a935fa0 R14: 00007f0e7a935fa0 R15: 0000000000000003
</TASK>
---
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@googlegroups.com.
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2)
2025-08-29 18:38 [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2) syzbot
@ 2025-08-30 0:06 ` syzbot
2025-08-30 0:45 ` Hillf Danton
1 sibling, 0 replies; 6+ messages in thread
From: syzbot @ 2025-08-30 0:06 UTC (permalink / raw)
To: bigeasy, bp, dave.hansen, hpa, linux-kernel, linux-sound, mingo,
perex, syzkaller-bugs, tglx, tiwai, x86
syzbot has bisected this issue to:
commit d2d6422f8bd17c6bb205133e290625a564194496
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri Sep 6 10:59:04 2024 +0000
x86: Allow to enable PREEMPT_RT.
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12db5634580000
start commit: 07d9df80082b Merge tag 'perf-tools-fixes-for-v6.17-2025-08..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=11db5634580000
console output: https://syzkaller.appspot.com/x/log.txt?x=16db5634580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
dashboard link: https://syzkaller.appspot.com/bug?extid=10b4363fb0f46527f3f3
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10307262580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17110242580000
Reported-by: syzbot+10b4363fb0f46527f3f3@syzkaller.appspotmail.com
Fixes: d2d6422f8bd1 ("x86: Allow to enable PREEMPT_RT.")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2)
2025-08-29 18:38 [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2) syzbot
2025-08-30 0:06 ` syzbot
@ 2025-08-30 0:45 ` Hillf Danton
2025-08-30 3:03 ` syzbot
1 sibling, 1 reply; 6+ messages in thread
From: Hillf Danton @ 2025-08-30 0:45 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
> Date: Fri, 29 Aug 2025 11:38:35 -0700 [thread overview]
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 07d9df80082b Merge tag 'perf-tools-fixes-for-v6.17-2025-08..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17333fbc580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
> dashboard link: https://syzkaller.appspot.com/bug?extid=10b4363fb0f46527f3f3
> compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=160e9262580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17ed0242580000
#syz test
--- x/kernel/time/hrtimer.c
+++ y/kernel/time/hrtimer.c
@@ -1718,7 +1718,7 @@ EXPORT_SYMBOL_GPL(hrtimer_active);
static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
struct hrtimer_clock_base *base,
struct hrtimer *timer, ktime_t *now,
- unsigned long flags) __must_hold(&cpu_base->lock)
+ unsigned long flags, bool soft) __must_hold(&cpu_base->lock)
{
enum hrtimer_restart (*fn)(struct hrtimer *);
bool expires_in_hardirq;
@@ -1755,6 +1755,8 @@ static void __run_hrtimer(struct hrtimer
* is dropped.
*/
raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+ if (soft)
+ hrtimer_cpu_base_unlock_expiry(cpu_base);
trace_hrtimer_expire_entry(timer, now);
expires_in_hardirq = lockdep_hrtimer_enter(timer);
@@ -1762,6 +1764,8 @@ static void __run_hrtimer(struct hrtimer
lockdep_hrtimer_exit(expires_in_hardirq);
trace_hrtimer_expire_exit(timer);
+ if (soft)
+ hrtimer_cpu_base_lock_expiry(cpu_base);
raw_spin_lock_irq(&cpu_base->lock);
/*
@@ -1822,7 +1826,8 @@ static void __hrtimer_run_queues(struct
if (basenow < hrtimer_get_softexpires_tv64(timer))
break;
- __run_hrtimer(cpu_base, base, timer, &basenow, flags);
+ __run_hrtimer(cpu_base, base, timer, &basenow, flags,
+ active_mask == HRTIMER_ACTIVE_SOFT);
if (active_mask == HRTIMER_ACTIVE_SOFT)
hrtimer_sync_wait_running(cpu_base, flags);
}
--
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2)
2025-08-30 0:45 ` Hillf Danton
@ 2025-08-30 3:03 ` syzbot
2025-08-30 6:56 ` Hillf Danton
0 siblings, 1 reply; 6+ messages in thread
From: syzbot @ 2025-08-30 3:03 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __snd_pcm_lib_xfer
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.46/6843 is trying to acquire lock:
ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168
but task is already holding lock:
ffff88814ccb7150 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&group->lock#2){+.+.}-{3:3}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56
spin_lock include/linux/spinlock_rt.h:44 [inline]
_snd_pcm_stream_lock_irqsave+0x7c/0xa0 sound/core/pcm_native.c:171
class_pcm_stream_lock_irqsave_constructor include/sound/pcm.h:682 [inline]
snd_pcm_period_elapsed+0x1e/0x80 sound/core/pcm_lib.c:1938
dummy_hrtimer_callback+0x80/0x180 sound/drivers/dummy.c:386
__run_hrtimer kernel/time/hrtimer.c:1763 [inline]
__hrtimer_run_queues+0x590/0xda0 kernel/time/hrtimer.c:1829
hrtimer_run_softirq+0x1a3/0x2e0 kernel/time/hrtimer.c:1847
handle_softirqs+0x22c/0x710 kernel/softirq.c:579
__do_softirq kernel/softirq.c:613 [inline]
run_ktimerd+0xcf/0x190 kernel/softirq.c:1043
smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #0 ((softirq_ctrl.lock)){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385
__lock_release kernel/locking/lockdep.c:5574 [inline]
lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889
__local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228
hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491
dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410
snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525
snd_pcm_action_single sound/core/pcm_native.c:1305 [inline]
snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388
__snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180
snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224
snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493
snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline]
__snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326
snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241
snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795
vfs_write+0x287/0xb40 fs/read_write.c:684
ksys_write+0x14b/0x260 fs/read_write.c:738
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:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&group->lock#2);
lock((softirq_ctrl.lock));
lock(&group->lock#2);
lock((softirq_ctrl.lock));
*** DEADLOCK ***
2 locks held by syz.0.46/6843:
#0: ffff88814ccb7150 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
#1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1bb/0x2c0 kernel/locking/spinlock_rt.c:57
stack backtrace:
CPU: 0 UID: 0 PID: 6843 Comm: syz.0.46 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385
__lock_release kernel/locking/lockdep.c:5574 [inline]
lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889
__local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228
hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491
dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410
snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525
snd_pcm_action_single sound/core/pcm_native.c:1305 [inline]
snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388
__snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180
snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224
snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493
snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline]
__snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326
snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241
snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795
vfs_write+0x287/0xb40 fs/read_write.c:684
ksys_write+0x14b/0x260 fs/read_write.c:738
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: 0033:0x7f9528fcebe9
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:00007f952863e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f95291f5fa0 RCX: 00007f9528fcebe9
RDX: 000000000000fc36 RSI: 0000200000000500 RDI: 0000000000000003
RBP: 00007f9529051e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f95291f6038 R14: 00007f95291f5fa0 R15: 00007ffe192e0268
</TASK>
Tested on:
commit: 11e7861d Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15d8d634580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bd9738e00c1bbfb4
dashboard link: https://syzkaller.appspot.com/bug?extid=10b4363fb0f46527f3f3
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=11b7fef0580000
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2)
2025-08-30 3:03 ` syzbot
@ 2025-08-30 6:56 ` Hillf Danton
2025-09-03 14:59 ` Sebastian Andrzej Siewior
0 siblings, 1 reply; 6+ messages in thread
From: Hillf Danton @ 2025-08-30 6:56 UTC (permalink / raw)
To: syzbot; +Cc: Sebastian Andrzej Siewior, linux-kernel, syzkaller-bugs
> Date: Fri, 29 Aug 2025 20:03:05 -0700
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> possible deadlock in __snd_pcm_lib_xfer
>
> ======================================================
> WARNING: possible circular locking dependency detected
> syzkaller #0 Not tainted
> ------------------------------------------------------
> syz.0.46/6843 is trying to acquire lock:
> ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
> ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168
>
Given softirq_ctrl is percpu, this report is false positive.
> but task is already holding lock:
> ffff88814ccb7150 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&group->lock#2){+.+.}-{3:3}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
> rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56
> spin_lock include/linux/spinlock_rt.h:44 [inline]
> _snd_pcm_stream_lock_irqsave+0x7c/0xa0 sound/core/pcm_native.c:171
> class_pcm_stream_lock_irqsave_constructor include/sound/pcm.h:682 [inline]
> snd_pcm_period_elapsed+0x1e/0x80 sound/core/pcm_lib.c:1938
> dummy_hrtimer_callback+0x80/0x180 sound/drivers/dummy.c:386
> __run_hrtimer kernel/time/hrtimer.c:1763 [inline]
> __hrtimer_run_queues+0x590/0xda0 kernel/time/hrtimer.c:1829
> hrtimer_run_softirq+0x1a3/0x2e0 kernel/time/hrtimer.c:1847
> handle_softirqs+0x22c/0x710 kernel/softirq.c:579
> __do_softirq kernel/softirq.c:613 [inline]
> run_ktimerd+0xcf/0x190 kernel/softirq.c:1043
> smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
> kthread+0x711/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> -> #0 ((softirq_ctrl.lock)){+.+.}-{3:3}:
> check_prev_add kernel/locking/lockdep.c:3165 [inline]
> check_prevs_add kernel/locking/lockdep.c:3284 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
> reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385
> __lock_release kernel/locking/lockdep.c:5574 [inline]
> lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889
> __local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228
> hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491
> dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410
> snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525
> snd_pcm_action_single sound/core/pcm_native.c:1305 [inline]
> snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388
> __snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180
> snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224
> snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493
> snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline]
> __snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326
> snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241
> snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
> snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
> snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
> snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795
> vfs_write+0x287/0xb40 fs/read_write.c:684
> ksys_write+0x14b/0x260 fs/read_write.c:738
> 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:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&group->lock#2);
> lock((softirq_ctrl.lock));
> lock(&group->lock#2);
> lock((softirq_ctrl.lock));
>
> *** DEADLOCK ***
>
> 2 locks held by syz.0.46/6843:
> #0: ffff88814ccb7150 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319
> #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
> #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
> #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1bb/0x2c0 kernel/locking/spinlock_rt.c:57
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 6843 Comm: syz.0.46 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
> check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
> check_prev_add kernel/locking/lockdep.c:3165 [inline]
> check_prevs_add kernel/locking/lockdep.c:3284 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
> reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385
> __lock_release kernel/locking/lockdep.c:5574 [inline]
> lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889
> __local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228
> hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491
> dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410
> snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525
> snd_pcm_action_single sound/core/pcm_native.c:1305 [inline]
> snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388
> __snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180
> snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224
> snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493
> snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline]
> __snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326
> snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241
> snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
> snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
> snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
> snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795
> vfs_write+0x287/0xb40 fs/read_write.c:684
> ksys_write+0x14b/0x260 fs/read_write.c:738
> 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: 0033:0x7f9528fcebe9
> 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:00007f952863e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007f95291f5fa0 RCX: 00007f9528fcebe9
> RDX: 000000000000fc36 RSI: 0000200000000500 RDI: 0000000000000003
> RBP: 00007f9529051e19 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f95291f6038 R14: 00007f95291f5fa0 R15: 00007ffe192e0268
> </TASK>
>
>
> Tested on:
>
> commit: 11e7861d Merge tag 'for-linus' of git://git.kernel.org..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15d8d634580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=bd9738e00c1bbfb4
> dashboard link: https://syzkaller.appspot.com/bug?extid=10b4363fb0f46527f3f3
> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> patch: https://syzkaller.appspot.com/x/patch.diff?x=11b7fef0580000
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2)
2025-08-30 6:56 ` Hillf Danton
@ 2025-09-03 14:59 ` Sebastian Andrzej Siewior
0 siblings, 0 replies; 6+ messages in thread
From: Sebastian Andrzej Siewior @ 2025-09-03 14:59 UTC (permalink / raw)
To: Hillf Danton; +Cc: syzbot, linux-kernel, syzkaller-bugs
On 2025-08-30 14:56:37 [+0800], Hillf Danton wrote:
> > syz.0.46/6843 is trying to acquire lock:
> > ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
> > ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168
> >
> Given softirq_ctrl is percpu, this report is false positive.
No. This can happen on a single CPU.
Sebastian
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-09-03 14:59 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2025-08-29 18:38 [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2) syzbot
2025-08-30 0:06 ` syzbot
2025-08-30 0:45 ` Hillf Danton
2025-08-30 3:03 ` syzbot
2025-08-30 6:56 ` Hillf Danton
2025-09-03 14:59 ` Sebastian Andrzej Siewior
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