syzbot


INFO: rcu detected stall in msync

Status: auto-obsoleted due to no activity on 2026/01/24 15:00
Subsystems: block
[Documentation on labels]
First crash: 116d, last: 101d

Sample crash report:
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:9e:7e:4e:b2:13:61, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10597/2:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=40445, q=3133 ncpus=1)
task:syz.0.790       state:R  running task     stack:27616 pid:10597 tgid:10583 ppid:5840   task_flags:0x20400040 flags:0x00080003
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7256
 irqentry_exit+0x36/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:deref_stack_reg arch/x86/kernel/unwind_orc.c:406 [inline]
RIP: 0010:unwind_next_frame+0xd10/0x20a0 arch/x86/kernel/unwind_orc.c:585
Code: 34 4c 89 ef 4c 89 44 24 28 48 89 4c 24 20 48 89 74 24 18 e8 f2 f0 ff ff 84 c0 0f 84 7c f6 ff ff 48 8b 7c 24 18 e8 d0 e8 ff ff <48> 89 ee 48 8b 4c 24 20 48 ba 00 00 00 00 00 fc ff df 48 c1 ee 03
RSP: 0018:ffffc9000433f0c8 EFLAGS: 00000202
RAX: ffffffff81a77e5e RBX: 0000000000000001 RCX: ffffc90004340000
RDX: ffffc9000433f201 RSI: ffffc9000433f220 RDI: ffffc9000433f220
RBP: ffffc9000433f1d0 R08: ffffffff9114a66a R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000006291 R12: ffffc9000433f1d8
R13: ffffc9000433f188 R14: ffffc9000433f228 R15: ffffc9000433f1bc
 __unwind_start+0x45f/0x7f0 arch/x86/kernel/unwind_orc.c:758
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0x73/0x100 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:559
 slab_free_hook mm/slub.c:2500 [inline]
 slab_free mm/slub.c:6630 [inline]
 kmem_cache_free+0x15e/0x6c0 mm/slub.c:6740
 mempool_free+0x102/0x750 mm/mempool.c:576
 bio_put_percpu_cache block/bio.c:805 [inline]
 bio_put+0x355/0x5b0 block/bio.c:824
 bio_endio+0x713/0x860 block/bio.c:1672
 blk_update_request+0x93e/0x15f0 block/blk-mq.c:998
 blk_mq_end_request+0x4f/0x90 block/blk-mq.c:1160
 blk_mq_complete_request block/blk-mq.c:1338 [inline]
 blk_mq_complete_request+0x8b/0xb0 block/blk-mq.c:1335
 nullb_complete_cmd drivers/block/null_blk/main.c:1402 [inline]
 null_handle_cmd drivers/block/null_blk/main.c:1454 [inline]
 null_queue_rq+0xb69/0xfd0 drivers/block/null_blk/main.c:1693
 null_queue_rqs+0xe9/0x2f0 drivers/block/null_blk/main.c:1707
 __blk_mq_flush_list block/blk-mq.c:2837 [inline]
 __blk_mq_flush_list+0x9a/0xc0 block/blk-mq.c:2833
 blk_mq_dispatch_queue_requests+0x184/0x7b0 block/blk-mq.c:2882
 blk_mq_flush_plug_list+0x1f2/0x600 block/blk-mq.c:2970
 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1225
 blk_finish_plug block/blk-core.c:1252 [inline]
 blk_finish_plug+0x53/0xa0 block/blk-core.c:1249
 blkdev_writepages+0xe9/0x140 block/fops.c:492
 do_writepages+0x27a/0x600 mm/page-writeback.c:2604
 filemap_fdatawrite_wbc mm/filemap.c:389 [inline]
 filemap_fdatawrite_wbc+0x104/0x160 mm/filemap.c:379
 __filemap_fdatawrite_range+0xb9/0x100 mm/filemap.c:422
 file_write_and_wait_range+0xca/0x140 mm/filemap.c:797
 blkdev_fsync+0x6c/0xd0 block/fops.c:623
 vfs_fsync_range+0x139/0x220 fs/sync.c:187
 __do_sys_msync+0x3cb/0x5c0 mm/msync.c:96
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f78b138efc9
RSP: 002b:00007f78af1f4038 EFLAGS: 00000246 ORIG_RAX: 000000000000001a
RAX: ffffffffffffffda RBX: 00007f78b15e6270 RCX: 00007f78b138efc9
RDX: 0000000000000006 RSI: 00000000000000e0 RDI: 0000000000000000
RBP: 00007f78b1411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f78b15e6308 R14: 00007f78b15e6270 R15: 00007fff3cfe6198
 </TASK>
rcu: rcu_preempt kthread starved for 684 jiffies! g40445 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:28552 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7026
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 3411 Comm: kworker/R-bat_e Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_tt_purge
RIP: 0010:debug_lockdep_rcu_enabled+0xa/0x40 kernel/rcu/update.c:320
Code: eb b6 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 8b 05 76 26 25 05 <85> c0 74 20 8b 05 e0 55 25 05 85 c0 74 16 65 48 8b 05 b8 f8 43 08
RSP: 0018:ffffc90000006a00 EFLAGS: 00000246
RAX: 0000000000000002 RBX: ffff88805ee71000 RCX: ffffffff8a08973c
RDX: ffff888030c7bc80 RSI: ffffffff8a089811 RDI: ffff88805ee32008
RBP: dffffc0000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88805ee32064
R13: ffffc90000006d10 R14: 0000000000000000 R15: ffff88805ee320c8
FS:  0000000000000000(0000) GS:ffff888124a10000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000d48000 CR3: 0000000077c60000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 __find_rr_leaf+0x23f/0xe00 net/ipv6/route.c:833
 find_rr_leaf net/ipv6/route.c:889 [inline]
 rt6_select net/ipv6/route.c:933 [inline]
 fib6_table_lookup+0x57c/0xa30 net/ipv6/route.c:2233
 ip6_pol_route+0x1cc/0x1230 net/ipv6/route.c:2269
 pol_lookup_func include/net/ip6_fib.h:617 [inline]
 fib6_rule_lookup+0x536/0x720 net/ipv6/fib6_rules.c:120
 ip6_route_input_lookup net/ipv6/route.c:2338 [inline]
 ip6_route_input+0x662/0xc70 net/ipv6/route.c:2641
 ip6_rcv_finish_core.constprop.0+0x1a0/0x5d0 net/ipv6/ip6_input.c:66
 ip6_rcv_finish+0x130/0x580 net/ipv6/ip6_input.c:77
 ip_sabotage_in+0x21e/0x290 net/bridge/br_netfilter_hooks.c:990
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xbe/0x200 net/netfilter/core.c:623
 nf_hook.constprop.0+0x424/0x750 include/linux/netfilter.h:273
 NF_HOOK include/linux/netfilter.h:316 [inline]
 ipv6_rcv+0xa4/0x650 net/ipv6/ip6_input.c:311
 __netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:6079
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
 netif_receive_skb_internal net/core/dev.c:6278 [inline]
 netif_receive_skb+0x137/0x7b0 net/core/dev.c:6337
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 br_pass_frame_up+0x346/0x490 net/bridge/br_input.c:70
 br_handle_frame_finish+0x10b7/0x1ec0 net/bridge/br_input.c:235
 br_nf_hook_thresh+0x307/0x410 net/bridge/br_netfilter_hooks.c:1167
 br_nf_pre_routing_finish_ipv6+0x76a/0xfc0 net/bridge/br_netfilter_ipv6.c:154
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x3cd/0x8c0 net/bridge/br_netfilter_ipv6.c:184
 br_nf_pre_routing+0x860/0x15b0 net/bridge/br_netfilter_hooks.c:508
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0xad8/0x14b0 net/bridge/br_input.c:442
 __netif_receive_skb_core.constprop.0+0xa25/0x4bd0 net/core/dev.c:5966
 __netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:6077
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
 process_backlog+0x439/0x15e0 net/core/dev.c:6544
 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7594
 napi_poll net/core/dev.c:7657 [inline]
 net_rx_action+0x97f/0xef0 net/core/dev.c:7784
 handle_softirqs+0x219/0x8e0 kernel/softirq.c:622
 do_softirq kernel/softirq.c:523 [inline]
 do_softirq+0xb2/0xf0 kernel/softirq.c:510
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:450
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 batadv_tt_global_purge net/batman-adv/translation-table.c:2250 [inline]
 batadv_tt_purge+0x25f/0xb80 net/batman-adv/translation-table.c:3510
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 rescuer_thread+0x620/0xea0 kernel/workqueue.c:3523
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
net_ratelimit: 4674 callbacks suppressed
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:9e:7e:4e:b2:13:61, 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)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:9e:7e:4e:b2:13:61, 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)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:9e:7e:4e:b2:13:61, vlan:0)
net_ratelimit: 5558 callbacks suppressed
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:9e:7e:4e:b2:13:61, 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)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:9e:7e:4e:b2:13:61, 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)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:9e:7e:4e:b2:13:61, vlan:0)

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/26 14:50 upstream 72761a7e3122 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in msync
2025/10/12 05:57 upstream 98906f9d850e ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in msync
* Struck through repros no longer work on HEAD.