syzbot


INFO: rcu detected stall in sys_sendto

Status: upstream: reported on 2025/08/26 10:53
Reported-by: syzbot+65b7d080de37a0d45cc4@syzkaller.appspotmail.com
First crash: 138d, last: 6d14h
Similar bugs (13)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_sendto (2) mm 1 93 2195d 2195d 0/29 closed as dup on 2020/01/08 06:15
upstream INFO: rcu detected stall in sys_sendto (6) net 1 1 780d 780d 0/29 closed as invalid on 2024/02/01 10:31
linux-6.1 INFO: rcu detected stall in sys_sendto origin:upstream 1 C error 1 492d 716d 0/3 auto-obsoleted due to no activity on 2025/10/30 02:21
linux-5.15 INFO: rcu detected stall in sys_sendto 1 1 515d 515d 0/3 auto-obsoleted due to no activity on 2024/11/22 09:09
upstream INFO: rcu detected stall in sys_sendto mm 1 357 2230d 2232d 0/29 closed as invalid on 2019/12/04 14:14
upstream INFO: rcu detected stall in sys_sendto (7) mm 1 C error 337 8h54m 600d 0/29 upstream: reported C repro on 2024/05/21 18:44
upstream INFO: rcu detected stall in sys_sendto (5) perf 1 7 1441d 1562d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_sendto (4) perf 1 1 2020d 2020d 0/29 auto-closed as invalid on 2020/09/29 07:17
linux-5.15 INFO: rcu detected stall in sys_sendto (2) origin:lts-only 1 syz done 2 314d 406d 0/3 upstream: reported syz repro on 2024/12/01 03:42
upstream INFO: rcu detected stall in sys_sendto (3) kernel 1 1 2098d 2098d 0/29 closed as invalid on 2020/05/21 18:32
linux-6.1 INFO: rcu detected stall in sys_sendto (2) origin:upstream 1 syz 1 30d 30d 0/3 upstream: reported syz repro on 2025/12/12 19:08
android-5-10 BUG: soft lockup in sys_sendto 1 2 879d 916d 0/2 auto-obsoleted due to no activity on 2023/11/14 13:19
android-5-15 BUG: soft lockup in sys_sendto 1 1 572d 572d 0/2 auto-obsoleted due to no activity on 2024/09/16 21:53

Sample crash report:
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 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): P5128/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=31209, q=41461 ncpus=2)
task:klogd           state:R  running task     stack:24232 pid:5128  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:unwind_get_return_address+0x4b/0xc0 arch/x86/kernel/unwind_orc.c:369
Code: e8 03 42 0f b6 04 30 84 c0 75 6e 8b 2b 31 ff 89 ee e8 99 f2 4a 00 85 ed 74 4a 48 83 c3 48 49 89 df 49 c1 ef 03 43 80 3c 37 00 <74> 08 48 89 df e8 bb 5c a2 00 48 8b 3b e8 13 d8 1d 00 89 c5 31 ff
RSP: 0018:ffffc900032971e0 EFLAGS: 00000246
RAX: ffffffff813aa1d7 RBX: ffffc90003297250 RCX: 0000000000000000
RDX: ffff88807de00000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff88807de00000 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff81dc267e
R13: 1ffff92000652e6c R14: dffffc0000000000 R15: 1ffff92000652e4a
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 save_stack+0xf7/0x1f0 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:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x31d/0x410 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 __kmem_cache_alloc_node+0x13e/0x260 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa2/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x116/0x240 net/core/skbuff.c:584
 __alloc_skb+0x138/0x2c0 net/core/skbuff.c:653
 alloc_skb include/linux/skbuff.h:1284 [inline]
 alloc_skb_with_frags+0xca/0x7c0 net/core/skbuff.c:6332
 sock_alloc_send_pskb+0x857/0x990 net/core/sock.c:2821
 unix_dgram_sendmsg+0x5a1/0x1720 net/unix/af_unix.c:2001
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 __sys_sendto+0x46a/0x620 net/socket.c:2201
 __do_sys_sendto net/socket.c:2213 [inline]
 __se_sys_sendto net/socket.c:2209 [inline]
 __x64_sys_sendto+0xde/0xf0 net/socket.c:2209
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc95a328407
RSP: 002b:00007ffe590bcef0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fc95a1d8c80 RCX: 00007fc95a328407
RDX: 0000000000000097 RSI: 00007ffe590bd030 RDI: 0000000000000003
RBP: 00007ffe590bd460 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000004000 R11: 0000000000000202 R12: 00007ffe590bd478
R13: 00007ffe590bd030 R14: 000000000000007c R15: 00007ffe590bd030
 </TASK>
rcu: rcu_preempt kthread starved for 1129 jiffies! g31209 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:26456 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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: 9413 Comm: syz.4.897 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:arch_stack_walk+0x1f/0x190 arch/x86/kernel/stacktrace.c:17
Code: 09 cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 48 89 e5 41 57 41 56 41 54 53 48 83 ec 68 49 89 cf 49 89 d4 48 89 f3 49 89 fe <65> 48 8b 04 25 28 00 00 00 48 89 45 d8 e8 1f 74 53 00 4d 85 ff 74
RSP: 0018:ffffc90000005908 EFLAGS: 00000292
RAX: ffffc900000059c0 RBX: ffffc900000059c0 RCX: 0000000000000000
RDX: ffff8880211f5a00 RSI: ffffc900000059c0 RDI: ffffffff81746d20
RBP: ffffc90000005990 R08: dffffc0000000000 R09: 0000000000000000
R10: ffffc90000005a40 R11: fffffbfff21b28b9 R12: ffff8880211f5a00
R13: ffffc90000005d20 R14: ffffffff81746d20 R15: 0000000000000000
FS:  00007f629574d6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555572e155c8 CR3: 000000006b6e9000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 skb_kfree_head net/core/skbuff.c:949 [inline]
 skb_free_head net/core/skbuff.c:961 [inline]
 skb_release_data+0x634/0x800 net/core/skbuff.c:991
 skb_release_all net/core/skbuff.c:1057 [inline]
 __kfree_skb net/core/skbuff.c:1071 [inline]
 consume_skb+0xb2/0x110 net/core/skbuff.c:1287
 nsim_start_xmit+0x9e/0xc0 drivers/net/netdevsim/netdev.c:42
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3619 [inline]
 dev_hard_start_xmit+0x246/0x740 net/core/dev.c:3635
 __dev_queue_xmit+0x1a64/0x35a0 net/core/dev.c:4425
 __bond_start_xmit include/linux/netdevice.h:-1 [inline]
 bond_start_xmit+0x1250/0x1c00 drivers/net/bonding/bond_main.c:5528
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3619 [inline]
 dev_hard_start_xmit+0x246/0x740 net/core/dev.c:3635
 __dev_queue_xmit+0x1a64/0x35a0 net/core/dev.c:4425
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 br_dev_queue_push_xmit+0x6a6/0x850 net/bridge/br_forward.c:53
 ip_do_fragment+0x877/0x1760 net/ipv4/ip_output.c:916
 NF_HOOK+0x613/0x6a0 include/linux/netfilter.h:304
 br_nf_post_routing+0xb41/0xfb0 net/bridge/br_netfilter_hooks.c:977
 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+0x213/0x3d0 include/linux/netfilter.h:302
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:-1 [inline]
 br_nf_forward_finish+0xa33/0xe50 net/bridge/br_netfilter_hooks.c:684
 NF_HOOK+0x613/0x6a0 include/linux/netfilter.h:304
 br_nf_forward_ip+0xcc1/0x1110 net/bridge/br_netfilter_hooks.c:754
 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+0x213/0x3d0 include/linux/netfilter.h:302
 __br_forward+0x41f/0x600 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+0x31b/0x680 net/bridge/br_forward.c:237
 br_handle_frame_finish+0x143d/0x1950 net/bridge/br_input.c:215
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:1184 [inline]
 br_nf_pre_routing_finish+0x147f/0x1ec0 net/bridge/br_netfilter_hooks.c:447
 NF_HOOK+0x613/0x6a0 include/linux/netfilter.h:304
 br_nf_pre_routing+0xe72/0x1420 net/bridge/br_netfilter_hooks.c:556
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
 br_handle_frame+0x957/0x14c0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xf6b/0x3ac0 net/core/dev.c:5502
 __netif_receive_skb_one_core net/core/dev.c:5606 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5722
 process_backlog+0x380/0x6e0 net/core/dev.c:6050
 __napi_poll+0xc0/0x460 net/core/dev.c:6612
 napi_poll net/core/dev.c:6679 [inline]
 net_rx_action+0x5ea/0xbf0 net/core/dev.c:6815
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 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:__sanitizer_cov_trace_pc+0x45/0x60 kernel/kcov.c:221
Code: ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 1c 16 00 00 00 74 2c 8b 91 f8 15 00 00 83 fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 <48> 8d 7e 01 8b 89 fc 15 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2
RSP: 0018:ffffc900050ffaf8 EFLAGS: 00000246
RAX: ffffffff813c0911 RBX: ffff8880269bb6c0 RCX: ffff8880211f5a00
RDX: ffffc900053b9000 RSI: 0000000000003c60 RDI: ffff8880269bb6c0
RBP: ffff8880269bc000 R08: ffffffff90d9452f R09: 1ffffffff21b28a5
R10: dffffc0000000000 R11: fffffbfff21b28a6 R12: ffff888019a4cc80
R13: dffffc0000000000 R14: ffffffff81dd0dba R15: ffff888019a4cc80
 __phys_addr+0x11/0x170 arch/x86/mm/physaddr.c:16
 virt_to_folio include/linux/mm.h:1289 [inline]
 virt_to_slab mm/slab.h:218 [inline]
 ___cache_free+0x1a/0x140 mm/slub.c:3837
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 __kmem_cache_alloc_node+0x13e/0x260 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 find_get_pmu_context+0x81/0x9e0 kernel/events/core.c:4902
 __do_sys_perf_event_open kernel/events/core.c:12821 [inline]
 __se_sys_perf_event_open+0xb49/0x1c20 kernel/events/core.c:12567
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f629498f749
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:00007f629574d038 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f6294be5fa0 RCX: 00007f629498f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000500
RBP: 00007f6294a13f91 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6294be6038 R14: 00007f6294be5fa0 R15: 00007ffd93924648
 </TASK>
net_ratelimit: 1848 callbacks suppressed
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
net_ratelimit: 2834 callbacks suppressed
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/05 10:17 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_sendto
2025/12/18 05:01 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_sendto
2025/10/01 01:54 linux-6.6.y 147338df3487 65a0eece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_sendto
2025/08/26 10:53 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_sendto
* Struck through repros no longer work on HEAD.