syzbot

 sign-in | mailing list | source | docs
🐞 Open [847]
🐞 Fixed [87]
🐞 Invalid [1279]
⬇ Missing Backports [132]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

INFO: rcu detected stall in br_ioctl_stub

Status: upstream: reported on 2026/01/03 21:20
Reported-by: syzbot+2c418506f23547356f3b@syzkaller.appspotmail.com
First crash: 101d, last: 3d01h
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in br_ioctl_stub 1 1 182d 182d 0/3 auto-obsoleted due to no activity on 2026/01/22 19:15
linux-6.1 INFO: rcu detected stall in br_ioctl_stub (2) 1 1 75d 75d 0/3 upstream: reported on 2026/01/30 08:26
upstream INFO: rcu detected stall in br_ioctl_stub mm 1 1 274d 274d 0/29 auto-obsoleted due to no activity on 2025/10/13 06:56
android-5-15 BUG: soft lockup in br_ioctl_stub 1 4 649d 720d 0/2 auto-obsoleted due to no activity on 2024/10/02 18:03

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 GPs behind) idle=4dd/1/0x4000000000000002 softirq=36719/36722 fqs=2100 
	(detected by 1, t=10502 jiffies, g=50345, q=1160)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 14131 Comm: syz.4.2399 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:check_preemption_disabled+0x0/0x110 lib/smp_processor_id.c:13
Code: 00 00 48 c7 c7 20 e8 32 8a e8 2c 01 00 00 65 ff 0d a1 db 46 76 5b c3 00 00 cc 48 c7 c7 20 f9 79 8a 48 c7 c6 60 f9 79 8a eb 00 <55> 41 57 41 56 53 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 44
RSP: 0018:ffffc90000007598 EFLAGS: 00000046
RAX: 1ffffffff2c64fe1 RBX: 0000000000000014 RCX: ffff88801dc33b80
RDX: 0000000000000100 RSI: ffffffff8a79f960 RDI: ffffffff8a79f920
RBP: 0000000000000001 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffffff8be31820
R13: dffffc0000000000 R14: ffffffff96327f08 R15: 0000607f46a16000
FS:  00007f227b7fa6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f227b7b8d58 CR3: 000000006492f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_trace_buf_alloc+0x178/0x300 kernel/trace/trace_event_perf.c:420
 perf_trace_preemptirq_template+0x180/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 12 f2 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900000077a0 EFLAGS: 00000206
RAX: 923605ef20f93c00 RBX: 1ffff92000000ef8 RCX: 923605ef20f93c00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f980
RBP: ffffc90000007880 R08: ffffffff901d40cf R09: 1ffffffff203a819
R10: dffffc0000000000 R11: fffffbfff203a81a R12: ffffffff8c322f00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 netif_receive_skb_list_internal+0x961/0xbd0 net/core/dev.c:5786
 gro_normal_list net/core/dev.c:5939 [inline]
 napi_complete_done+0x378/0x850 net/core/dev.c:6677
 virtqueue_napi_complete drivers/net/virtio_net.c:357 [inline]
 virtnet_poll+0x955/0xf40 drivers/net/virtio_net.c:1624
 __napi_poll+0xc0/0x430 net/core/dev.c:7101
 napi_poll net/core/dev.c:7168 [inline]
 net_rx_action+0x4d4/0xa10 net/core/dev.c:7258
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__next_zones_zonelist+0x0/0x130 mm/mmzone.c:59
Code: 80 e1 07 80 c1 03 38 c1 0f 8c 6d ff ff ff 4c 89 f7 e8 14 43 16 00 e9 60 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <55> 41 57 41 56 41 55 41 54 53 89 f3 49 89 fe 48 bd 00 00 00 00 00
RSP: 0018:ffffc90003c27368 EFLAGS: 00000282
RAX: 1ffff92000784e85 RBX: ffffc90003c2743c RCX: 0000000000000000
RDX: ffff88801dc34e98 RSI: 0000000000000002 RDI: ffff88813fffd300
RBP: 0000000000000002 R08: dffffc0000000000 R09: 1ffffffff1b13c6d
R10: dffffc0000000000 R11: fffffbfff1b13c6e R12: 0000000000000000
R13: ffff88813fffd300 R14: ffffc90003c27428 R15: 1ffff92000784e84
 next_zones_zonelist include/linux/mmzone.h:1168 [inline]
 first_zones_zonelist include/linux/mmzone.h:1192 [inline]
 prepare_alloc_pages+0x368/0x5f0 mm/page_alloc.c:5290
 __alloc_pages+0x11b/0x480 mm/page_alloc.c:5490
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x195/0x290 mm/slub.c:3238
 kmem_cache_zalloc include/linux/slab.h:728 [inline]
 __kernfs_new_node+0xe3/0x6c0 fs/kernfs/dir.c:593
 kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:669
 __kernfs_create_file+0x47/0x2e0 fs/kernfs/file.c:985
 sysfs_add_file_mode_ns+0x2d4/0x3a0 fs/sysfs/file.c:317
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x495/0xd00 fs/sysfs/group.c:149
 internal_create_groups fs/sysfs/group.c:189 [inline]
 sysfs_create_groups+0x55/0x120 fs/sysfs/group.c:215
 device_add_groups drivers/base/core.c:2491 [inline]
 device_add_attrs+0x137/0x6a0 drivers/base/core.c:2650
 device_add+0x64b/0xfb0 drivers/base/core.c:3363
 netdev_register_kobject+0x184/0x320 net/core/net-sysfs.c:2014
 register_netdevice+0x1042/0x1710 net/core/dev.c:10423
 br_add_bridge+0x9f/0xe0 net/bridge/br_if.c:460
 br_ioctl_stub+0x4f5/0xbe0 net/bridge/br_ioctl.c:416
 br_ioctl_call net/socket.c:1121 [inline]
 sock_ioctl+0x494/0x710 net/socket.c:1220
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f227d5a0819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f227b7fa028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f227d819fa0 RCX: 00007f227d5a0819
RDX: 0000200000000080 RSI: 00000000000089a0 RDI: 000000000000000d
RBP: 00007f227d636c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f227d81a038 R14: 00007f227d819fa0 R15: 00007ffe7d5b5bd8
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/12 15:40 linux-5.15.y 91d48252ad4b 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in br_ioctl_stub
2026/01/03 21:19 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in br_ioctl_stub
* Struck through repros no longer work on HEAD.