syzbot
INFO: rcu detected stall in sys_recvmsg (2)
Status:
upstream: reported on 2026/10/04 09:06
Reported-by: syzbot+5348e6432ebe90254dd1@syzkaller.appspotmail.com
First crash: 4d06h, last: 4d06h
Sample crash report:
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P15540/1:b..l
rcu: (detected by 1, t=10503 jiffies, g=118957, q=322 ncpus=2)
task:syz-executor state:R running task stack:21800 pid:15540 ppid:15520 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6868
preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6892
preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
unwind_next_frame+0x201c/0x2990 arch/x86/kernel/unwind_orc.c:672
arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
save_stack+0x125/0x230 mm/page_owner.c:128
__reset_page_owner+0x4e/0x190 mm/page_owner.c:149
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1182 [inline]
free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
__slab_free+0x35a/0x400 mm/slub.c:3736
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
____kasan_kmalloc mm/kasan/common.c:341 [inline]
__kasan_kmalloc+0x22/0xa0 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slab_common.c:1007 [inline]
__kmalloc+0xb7/0x240 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
kzalloc include/linux/slab.h:721 [inline]
tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
tomoyo_encode+0x2ad/0x570 security/tomoyo/realpath.c:80
tomoyo_realpath_from_path+0x57c/0x5c0 security/tomoyo/realpath.c:283
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_check_open_permission+0x224/0x460 security/tomoyo/file.c:771
security_file_open+0x62/0xa0 security/security.c:2968
do_dentry_open+0x32b/0x14b0 fs/open.c:916
do_open fs/namei.c:3683 [inline]
path_openat+0x284f/0x3270 fs/namei.c:3844
do_filp_open+0x1f2/0x430 fs/namei.c:3871
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f575839d47c
RSP: 002b:00007fffea861300 EFLAGS: 00000206 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f57584344bb RCX: 00007f575839d47c
RDX: 0000000000090800 RSI: 00007fffea8624b0 RDI: 00000000ffffff9c
RBP: 00007fffea86249c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fffea8624b0
R13: 00007f57584344bb R14: 00000000000e25ae R15: 00007fffea8624f0
</TASK>
rcu: rcu_preempt kthread starved for 1013 jiffies! g118957 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:R running task stack:25320 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x30d/0x1590 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 19136 Comm: syz.1.4272 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:__sanitizer_cov_trace_switch+0x46/0xe0 kernel/kcov.c:-1
Code: 48 0f bc c8 48 83 c1 fd 48 83 f9 03 0f 87 b0 00 00 00 48 8b 06 48 85 c0 0f 84 a4 00 00 00 41 57 41 56 41 54 53 48 8d 4c 09 01 <48> 8b 54 24 20 65 4c 8b 05 3d 22 7c 7e 45 31 c9 eb 08 49 ff c1 4c
RSP: 0018:ffffc900000069f0 EFLAGS: 00000206
RAX: 0000000000000003 RBX: ffffffff8f9a598d RCX: 0000000000000003
RDX: 000000000000001f RSI: ffffffff8cfa0950 RDI: 0000000000000002
RBP: ffffc900000077c0 R08: ffff8880275cbc00 R09: 0000000000000008
R10: 0000000000000009 R11: 0000000000000100 R12: ffffffff8f9a598c
R13: ffffc90000006ae8 R14: 0000000000000002 R15: dffffc0000000000
FS: 00007f28bd7246c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555ffaf4e8 CR3: 000000005ee7c000 CR4: 00000000003506f0
DR0: 0100000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
unwind_next_frame+0xe42/0x2990 arch/x86/kernel/unwind_orc.c:581
arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519
skb_ext_maybe_cow net/core/skbuff.c:6709 [inline]
skb_ext_add+0x1b3/0x8e0 net/core/skbuff.c:6783
nf_bridge_unshare net/bridge/br_netfilter_hooks.c:165 [inline]
br_nf_forward_ip+0xc6/0x10d0 net/bridge/br_netfilter_hooks.c:713
nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
nf_hook include/linux/netfilter.h:259 [inline]
NF_HOOK+0x23e/0x3e0 include/linux/netfilter.h:302
__br_forward+0x433/0x610 net/bridge/br_forward.c:115
deliver_clone net/bridge/br_forward.c:131 [inline]
maybe_deliver+0xb5/0x150 net/bridge/br_forward.c:191
br_flood+0x317/0x670 net/bridge/br_forward.c:237
br_handle_frame_finish+0xf2d/0x15c0 net/bridge/br_input.c:215
br_nf_hook_thresh+0x3cd/0x4a0 net/bridge/br_netfilter_hooks.c:1188
br_nf_pre_routing_finish_ipv6+0x9e5/0xd20 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:304 [inline]
br_nf_pre_routing_ipv6+0x34d/0x6a0 net/bridge/br_netfilter_ipv6.c:184
nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
br_handle_frame+0x1240/0x14d0 net/bridge/br_input.c:424
__netif_receive_skb_core+0xf94/0x3ac0 net/core/dev.c:5564
__netif_receive_skb_one_core net/core/dev.c:5668 [inline]
__netif_receive_skb+0x74/0x290 net/core/dev.c:5784
process_backlog+0x380/0x710 net/core/dev.c:6112
__napi_poll+0xbb/0x460 net/core/dev.c:6674
napi_poll net/core/dev.c:6741 [inline]
net_rx_action+0x65f/0xcc0 net/core/dev.c:6877
handle_softirqs+0x27d/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:preempt_schedule+0x92/0xd0 kernel/sched/core.c:6893
Code: 48 b8 04 00 00 00 00 fc ff df c6 04 03 00 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 c6 04 03 f8 75 29 <48> c7 04 24 0e 36 e0 45 4a c7 04 33 00 00 00 00 65 48 8b 04 25 28
RSP: 0018:ffffc9000e8efba0 EFLAGS: 00000246
RAX: 1ffff11004eb9780 RBX: 1ffff92001d1df74 RCX: 67d34a580a942300
RDX: dffffc0000000000 RSI: ffffffff8acacce0 RDI: ffffffff8b1d4020
RBP: ffffc9000e8efc18 R08: ffffffff8e8c626f R09: 1ffffffff1d18c4d
R10: dffffc0000000000 R11: fffffbfff1d18c4e R12: dffffc0000000000
R13: ffff8880275cbc00 R14: dffffc0000000000 R15: 000000002b5c0000
preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
rcu_read_unlock_sched include/linux/rcupdate.h:901 [inline]
pfn_valid include/linux/mmzone.h:2021 [inline]
__virt_addr_valid+0x325/0x380 arch/x86/mm/physaddr.c:65
kasan_addr_to_slab+0xd/0xd0 mm/kasan/common.c:36
__kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:477
task_work_add+0xdd/0x470 kernel/task_work.c:82
fput+0xdd/0x1a0 fs/file_table.c:474
fput_light include/linux/file.h:34 [inline]
__sys_recvmsg net/socket.c:2888 [inline]
__do_sys_recvmsg net/socket.c:2896 [inline]
__se_sys_recvmsg net/socket.c:2893 [inline]
__x64_sys_recvmsg+0x278/0x2f0 net/socket.c:2893
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f28bc79e159
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:00007f28bd724028 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 00007f28bca25fa0 RCX: 00007f28bc79e159
RDX: 0000000000000000 RSI: 00002000000003c0 RDI: 000000000000001a
RBP: 00007f28bc83506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f28bca26038 R14: 00007f28bca25fa0 R15: 00007fff3aee3fb8
</TASK>
net_ratelimit: 1014 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:0e:cb:c5:36:b5:f5, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
net_ratelimit: 4455 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:0e:cb:c5:36:b5:f5, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
* Struck through repros no longer work on HEAD.