syzbot


general protection fault in loopback_jiffies_timer_pos_update

Status: upstream: reported on 2026/05/18 14:08
Reported-by: syzbot+ab669cc0b6618d92cadc@syzkaller.appspotmail.com
First crash: 3d10h, last: 3d10h
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in loopback_jiffies_timer_pos_update sound 2 1 1017d 1013d 0/29 auto-obsoleted due to no activity on 2023/11/06 13:26
linux-6.6 general protection fault in loopback_jiffies_timer_pos_update origin:upstream missing-backport 2 syz error 3 77d 272d 0/2 upstream: reported syz repro on 2025/08/22 01:56
upstream general protection fault in loopback_jiffies_timer_pos_update (2) sound 2 1 298d 294d 0/29 auto-obsoleted due to no activity on 2025/10/25 12:37
upstream BUG: unable to handle kernel NULL pointer dereference in loopback_jiffies_timer_pos_update sound 10 1 1340d 1336d 0/29 auto-obsoleted due to no activity on 2022/12/18 13:48

Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc0000000009: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f]
CPU: 0 PID: 5504 Comm: kworker/u4:14 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: netns cleanup_net
RIP: 0010:loopback_jiffies_timer_pos_update+0x138/0x1250 sound/drivers/aloop.c:619
Code: 9e 7d f9 44 89 f8 83 e0 02 44 89 7c 24 3c 75 0a e8 4d 9b 7d f9 45 31 ff eb 27 e8 43 9b 7d f9 49 8d 5d 48 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 08 48 89 df e8 6a a7 ce f9 4d 89 f7 4c 2b 3b 4c 89
RSP: 0018:ffffc90000007a88 EFLAGS: 00010006
RAX: 0000000000000009 RBX: 0000000000000048 RCX: ffff88802eba5940
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffffffff8e1ffbef R09: 1ffffffff1c3ff7d
R10: dffffc0000000000 R11: fffffbfff1c3ff7e R12: 0000000000000000
R13: 0000000000000000 R14: 00000000ffffce1a R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000088000 CR3: 00000000571e0000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 loopback_jiffies_timer_function+0x5e/0x240 sound/drivers/aloop.c:662
 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:2023
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:preempt_schedule_irq+0xb6/0x160 kernel/sched/core.c:6874
Code: 00 00 43 c6 44 37 04 f8 74 0b 0f 0b 48 f7 03 08 00 00 00 74 7f bf 01 00 00 00 e8 65 65 22 f7 e8 70 59 52 f7 fb bf 01 00 00 00 <e8> 75 b9 ff ff 43 c6 44 37 08 00 48 c7 44 24 40 00 00 00 00 9c 8f
RSP: 0018:ffffc90003d6f5c0 EFLAGS: 00000282
RAX: c5e073e22f54ae00 RBX: 0000000000000000 RCX: c5e073e22f54ae00
RDX: dffffc0000000000 RSI: ffffffff8a8c19a0 RDI: 0000000000000001
RBP: ffffc90003d6f660 R08: ffffffff90afa24f R09: 1ffffffff215f449
R10: dffffc0000000000 R11: fffffbfff215f44a R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff920007adeb8
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:696
RIP: 0010:lockdep_unregister_key+0x4e8/0x550 kernel/locking/lockdep.c:6370
Code: a1 aa 90 48 c7 c6 70 f7 64 81 e8 73 a8 07 00 e8 de bb 07 00 e9 5c fc ff ff e8 d4 fe c8 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b eb 88 0f 0b e9 f8 fe ff ff 0f 0b e9 45 ff ff ff
RSP: 0018:ffffc90003d6f720 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: c5e073e22f54ae00
RDX: 0000000000000001 RSI: ffffffff8a8c2680 RDI: ffffffff8adf1ba0
RBP: ffffc90003d6f800 R08: ffffffff90acbdd7 R09: 1ffffffff21597ba
R10: dffffc0000000000 R11: fffffbfff21597bb R12: 0000000000000207
R13: ffff88802a7e3a99 R14: ffffffff90aca1a8 R15: 1ffff920007adee8
 __qdisc_destroy+0x128/0x430 net/sched/sch_generic.c:1081
 netdev_for_each_tx_queue include/linux/netdevice.h:2465 [inline]
 dev_shutdown+0x92/0x440 net/sched/sch_generic.c:1465
 unregister_netdevice_many_notify+0xa76/0x19c0 net/core/dev.c:11014
 unregister_netdevice_many net/core/dev.c:11077 [inline]
 default_device_exit_batch+0x9ea/0xa80 net/core/dev.c:11549
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x791/0xba0 net/core/net_namespace.c:640
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:loopback_jiffies_timer_pos_update+0x138/0x1250 sound/drivers/aloop.c:619
Code: 9e 7d f9 44 89 f8 83 e0 02 44 89 7c 24 3c 75 0a e8 4d 9b 7d f9 45 31 ff eb 27 e8 43 9b 7d f9 49 8d 5d 48 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 08 48 89 df e8 6a a7 ce f9 4d 89 f7 4c 2b 3b 4c 89
RSP: 0018:ffffc90000007a88 EFLAGS: 00010006
RAX: 0000000000000009 RBX: 0000000000000048 RCX: ffff88802eba5940
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffffffff8e1ffbef R09: 1ffffffff1c3ff7d
R10: dffffc0000000000 R11: fffffbfff1c3ff7e R12: 0000000000000000
R13: 0000000000000000 R14: 00000000ffffce1a R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000088000 CR3: 00000000571e0000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
   0:	9e                   	sahf
   1:	7d f9                	jge    0xfffffffc
   3:	44 89 f8             	mov    %r15d,%eax
   6:	83 e0 02             	and    $0x2,%eax
   9:	44 89 7c 24 3c       	mov    %r15d,0x3c(%rsp)
   e:	75 0a                	jne    0x1a
  10:	e8 4d 9b 7d f9       	call   0xf97d9b62
  15:	45 31 ff             	xor    %r15d,%r15d
  18:	eb 27                	jmp    0x41
  1a:	e8 43 9b 7d f9       	call   0xf97d9b62
  1f:	49 8d 5d 48          	lea    0x48(%r13),%rbx
  23:	48 89 d8             	mov    %rbx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	48 89 df             	mov    %rbx,%rdi
  33:	e8 6a a7 ce f9       	call   0xf9cea7a2
  38:	4d 89 f7             	mov    %r14,%r15
  3b:	4c 2b 3b             	sub    (%rbx),%r15
  3e:	4c                   	rex.WR
  3f:	89                   	.byte 0x89

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/18 14:07 linux-6.1.y c27210688955 55156e84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan general protection fault in loopback_jiffies_timer_pos_update
* Struck through repros no longer work on HEAD.