[v6.1] INFO: rcu detected stall in br_ioctl_stub (3)
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syzbot
Jul 29, 2026, 9:42:24 AMJul 29
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1168caa9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=289d0c8c3fa41622e6a9
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/20011e25c344/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/da97f6113bb4/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3d98353da44a/bzImage-dc5c83b7.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+289d0c...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2670 jiffies s: 63709 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 16218 Comm: syz.3.4178 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__nr_to_section include/linux/mmzone.h:1695 [inline]
RIP: 0010:__pfn_to_section include/linux/mmzone.h:1803 [inline]
RIP: 0010:pfn_valid include/linux/mmzone.h:1856 [inline]
RIP: 0010:__virt_addr_valid+0x134/0x540 arch/x86/mm/physaddr.c:65
Code: 20 00 74 0c 48 c7 c7 20 00 c7 96 e8 56 72 99 00 48 8b 05 bf 11 8d 15 48 85 c0 74 42 48 89 d9 48 c1 e9 22 4c 8d 34 c8 4c 89 f0 <48> c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 29 72 99 00 4d 8b 3e
RSP: 0018:ffffc900001e05e0 EFLAGS: 00000046
RAX: ffff88823ffef000 RBX: 00000000b8f3bbf0 RCX: 0000000000000000
RDX: 0000000000000100 RSI: 00000000b8f3bbf0 RDI: 00003fffffffffff
RBP: 0000000000000001 R08: ffff8880b8f3bbfb R09: 1ffff110171e777f
R10: dffffc0000000000 R11: ffffed10171e7780 R12: dffffc0000000000
R13: dffffc0000000001 R14: ffff88823ffef000 R15: 0000000000000000
FS: 00007ff27d3af6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff27c5eb580 CR3: 000000013febe000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
kasan_addr_to_slab+0x9/0xc0 mm/kasan/common.c:36
__kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:471
irq_work_queue_on+0x10f/0x260 kernel/irq_work.c:140
rcu_read_unlock_special+0x3c9/0x510 kernel/rcu/tree_plugin.h:678
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
trace_call_bpf+0x5bb/0x6b0 kernel/trace/bpf_trace.c:137
perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:10027
perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
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 a2 7c 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0ae0 EFLAGS: 00000206
RAX: 2b95d2ab9ab3e600 RBX: 1ffff9200003c164 RCX: 2b95d2ab9ab3e600
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adf5de0
RBP: ffffc900001e0bd0 R08: ffffffff90b0f24f R09: 1ffffffff2161e49
R10: dffffc0000000000 R11: fffffbfff2161e4a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3bb00 R15: 0000000000000002
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1751 [inline]
__hrtimer_run_queues+0x522/0xc90 kernel/time/hrtimer.c:1815
hrtimer_run_softirq+0x173/0x290 kernel/time/hrtimer.c:1832
handle_softirqs+0x291/0x910 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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:244 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x4/0x80 kernel/kcov.c:313
Code: 77 22 89 ff 89 f6 49 ff c0 4c 89 01 48 c7 44 11 08 03 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 48 8b 04 24 <65> 48 8b 15 e4 37 80 7e 65 8b 0d e5 37 80 7e 81 e1 00 01 ff 00 74
RSP: 0018:ffffc90003dd76f8 EFLAGS: 00000246
RAX: ffffffff8205baaf RBX: ffffffff8b981280 RCX: 0000000000000072
RDX: 000000000000000c RSI: 00000000fffffffc RDI: 0000000000000000
RBP: ffff888058ad5150 R08: 0000000000000000 R09: ffff888058ad56b8
R10: dffffc0000000000 R11: ffffed100b15aad9 R12: 000000000000000c
R13: 00000000fffffffc R14: ffff888058ad5078 R15: 00000000fffffff0
namecmp fs/proc/proc_sysctl.c:114 [inline]
insert_entry fs/proc/proc_sysctl.c:172 [inline]
insert_header+0x98f/0xdb0 fs/proc/proc_sysctl.c:252
__register_sysctl_table+0xdde/0xed0 fs/proc/proc_sysctl.c:1385
__addrconf_sysctl_register+0x271/0x3e0 net/ipv6/addrconf.c:7165
addrconf_sysctl_register+0x15c/0x1b0 net/ipv6/addrconf.c:7212
ipv6_add_dev+0xbd4/0x1110 net/ipv6/addrconf.c:451
addrconf_notify+0x634/0xf60 net/ipv6/addrconf.c:3602
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
call_netdevice_notifiers_extack net/core/dev.c:2052 [inline]
call_netdevice_notifiers net/core/dev.c:2066 [inline]
register_netdevice+0x16a8/0x1b80 net/core/dev.c:10276
br_add_bridge+0x9f/0xe0 net/bridge/br_if.c:473
br_ioctl_stub+0x5e2/0xcf0 net/bridge/br_ioctl.c:442
br_ioctl_call net/socket.c:1176 [inline]
sock_ioctl+0x453/0x700 net/socket.c:1275
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff27c59de99
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:00007ff27d3af028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff27c825fa0 RCX: 00007ff27c59de99
RDX: 0000200000000080 RSI: 00000000000089a0 RDI: 000000000000000e
RBP: 00007ff27c633eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff27c826038 R14: 00007ff27c825fa0 R15: 00007ffec6cc7648
</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 syzk...@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 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
syzbot found the following issue on:
HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1168caa9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=289d0c8c3fa41622e6a9
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/20011e25c344/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/da97f6113bb4/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3d98353da44a/bzImage-dc5c83b7.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+289d0c...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2670 jiffies s: 63709 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 16218 Comm: syz.3.4178 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__nr_to_section include/linux/mmzone.h:1695 [inline]
RIP: 0010:__pfn_to_section include/linux/mmzone.h:1803 [inline]
RIP: 0010:pfn_valid include/linux/mmzone.h:1856 [inline]
RIP: 0010:__virt_addr_valid+0x134/0x540 arch/x86/mm/physaddr.c:65
Code: 20 00 74 0c 48 c7 c7 20 00 c7 96 e8 56 72 99 00 48 8b 05 bf 11 8d 15 48 85 c0 74 42 48 89 d9 48 c1 e9 22 4c 8d 34 c8 4c 89 f0 <48> c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 29 72 99 00 4d 8b 3e
RSP: 0018:ffffc900001e05e0 EFLAGS: 00000046
RAX: ffff88823ffef000 RBX: 00000000b8f3bbf0 RCX: 0000000000000000
RDX: 0000000000000100 RSI: 00000000b8f3bbf0 RDI: 00003fffffffffff
RBP: 0000000000000001 R08: ffff8880b8f3bbfb R09: 1ffff110171e777f
R10: dffffc0000000000 R11: ffffed10171e7780 R12: dffffc0000000000
R13: dffffc0000000001 R14: ffff88823ffef000 R15: 0000000000000000
FS: 00007ff27d3af6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff27c5eb580 CR3: 000000013febe000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
kasan_addr_to_slab+0x9/0xc0 mm/kasan/common.c:36
__kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:471
irq_work_queue_on+0x10f/0x260 kernel/irq_work.c:140
rcu_read_unlock_special+0x3c9/0x510 kernel/rcu/tree_plugin.h:678
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
trace_call_bpf+0x5bb/0x6b0 kernel/trace/bpf_trace.c:137
perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:10027
perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
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 a2 7c 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0ae0 EFLAGS: 00000206
RAX: 2b95d2ab9ab3e600 RBX: 1ffff9200003c164 RCX: 2b95d2ab9ab3e600
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adf5de0
RBP: ffffc900001e0bd0 R08: ffffffff90b0f24f R09: 1ffffffff2161e49
R10: dffffc0000000000 R11: fffffbfff2161e4a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3bb00 R15: 0000000000000002
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1751 [inline]
__hrtimer_run_queues+0x522/0xc90 kernel/time/hrtimer.c:1815
hrtimer_run_softirq+0x173/0x290 kernel/time/hrtimer.c:1832
handle_softirqs+0x291/0x910 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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:244 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x4/0x80 kernel/kcov.c:313
Code: 77 22 89 ff 89 f6 49 ff c0 4c 89 01 48 c7 44 11 08 03 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 48 8b 04 24 <65> 48 8b 15 e4 37 80 7e 65 8b 0d e5 37 80 7e 81 e1 00 01 ff 00 74
RSP: 0018:ffffc90003dd76f8 EFLAGS: 00000246
RAX: ffffffff8205baaf RBX: ffffffff8b981280 RCX: 0000000000000072
RDX: 000000000000000c RSI: 00000000fffffffc RDI: 0000000000000000
RBP: ffff888058ad5150 R08: 0000000000000000 R09: ffff888058ad56b8
R10: dffffc0000000000 R11: ffffed100b15aad9 R12: 000000000000000c
R13: 00000000fffffffc R14: ffff888058ad5078 R15: 00000000fffffff0
namecmp fs/proc/proc_sysctl.c:114 [inline]
insert_entry fs/proc/proc_sysctl.c:172 [inline]
insert_header+0x98f/0xdb0 fs/proc/proc_sysctl.c:252
__register_sysctl_table+0xdde/0xed0 fs/proc/proc_sysctl.c:1385
__addrconf_sysctl_register+0x271/0x3e0 net/ipv6/addrconf.c:7165
addrconf_sysctl_register+0x15c/0x1b0 net/ipv6/addrconf.c:7212
ipv6_add_dev+0xbd4/0x1110 net/ipv6/addrconf.c:451
addrconf_notify+0x634/0xf60 net/ipv6/addrconf.c:3602
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
call_netdevice_notifiers_extack net/core/dev.c:2052 [inline]
call_netdevice_notifiers net/core/dev.c:2066 [inline]
register_netdevice+0x16a8/0x1b80 net/core/dev.c:10276
br_add_bridge+0x9f/0xe0 net/bridge/br_if.c:473
br_ioctl_stub+0x5e2/0xcf0 net/bridge/br_ioctl.c:442
br_ioctl_call net/socket.c:1176 [inline]
sock_ioctl+0x453/0x700 net/socket.c:1275
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff27c59de99
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:00007ff27d3af028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff27c825fa0 RCX: 00007ff27c59de99
RDX: 0000200000000080 RSI: 00000000000089a0 RDI: 000000000000000e
RBP: 00007ff27c633eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff27c826038 R14: 00007ff27c825fa0 R15: 00007ffec6cc7648
</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 syzk...@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 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
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