syzbot


INFO: rcu detected stall in sys_fdatasync

Status: auto-obsoleted due to no activity on 2026/02/22 10:38
Subsystems: modules
[Documentation on labels]
First crash: 126d, last: 126d

Sample crash report:
bridge0: received packet on veth0_to_bridge with own address as source address (addr:02:30:c6:0b:32:19, vlan:0)
bridge0: received packet on veth0_to_bridge 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): P13082/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=64765, q=1034 ncpus=1)
task:syz.0.2037      state:R  running task     stack:27576 pid:13082 tgid:13078 ppid:5826   task_flags:0x20400040 flags:0x00080001
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:__rcu_read_unlock+0x11b/0x550 kernel/rcu/tree_plugin.h:445
Code: 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 7d 01 00 00 8b 83 84 04 00 00 3d ff ff ff 3f 0f 87 51 01 00 00 5b 5d <41> 5c 41 5d 41 5e e9 9a 30 be 09 65 8b 1d 23 b9 fe 11 f7 c3 00 00
RSP: 0018:ffffc90004437118 EFLAGS: 00000293
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffc900044370fc
RDX: 0000000000000000 RSI: ffffffff8da0398a RDI: ffff8880252422c4
RBP: 00007f23d0f8f749 R08: f501fefe41178ce3 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888025241e40
R13: ffffc90004437258 R14: 0000000000000000 R15: ffff888025241e40
 rcu_read_unlock include/linux/rcupdate.h:899 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1195 [inline]
 is_module_text_address+0x152/0x220 kernel/module/main.c:3845
 kernel_text_address kernel/extable.c:119 [inline]
 kernel_text_address+0x81/0x100 kernel/extable.c:94
 __kernel_text_address+0xd/0x40 kernel/extable.c:79
 unwind_get_return_address+0x59/0xa0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0xa6/0x100 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
 kasan_save_track+0x14/0x30 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417
 kmalloc_noprof include/linux/slab.h:957 [inline]
 slab_free_hook mm/slub.c:2495 [inline]
 slab_free mm/slub.c:6642 [inline]
 kmem_cache_free+0x147/0x6c0 mm/slub.c:6752
 mempool_free+0x102/0x750 mm/mempool.c:596
 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
 vfs_fsync fs/sync.c:201 [inline]
 do_fsync+0x4b/0xa0 fs/sync.c:212
 __do_sys_fdatasync fs/sync.c:222 [inline]
 __se_sys_fdatasync fs/sync.c:220 [inline]
 __x64_sys_fdatasync+0x35/0x50 fs/sync.c:220
 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: 0033:0x7f23d0f8f749
RSP: 002b:00007f23d1dd5038 EFLAGS: 00000246 ORIG_RAX: 000000000000004b
RAX: ffffffffffffffda RBX: 00007f23d11e6090 RCX: 00007f23d0f8f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f23d1013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f23d11e6128 R14: 00007f23d11e6090 R15: 00007ffedd52c578
 </TASK>
rcu: rcu_preempt kthread starved for 747 jiffies! g64765 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: 3408 Comm: kworker/R-bat_e Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: bat_events batadv_dat_purge
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x70 kernel/kcov.c:210
Code: 46 81 56 00 48 89 df 5b e9 ed 2e 5c 00 be 03 00 00 00 5b e9 c2 93 e5 02 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 48 8b 34 24 65 48 8b 15 78 d8 e4 11 65 8b 05 89 d8 e4
RSP: 0018:ffffc900000073c0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: ffffffff8a086b5b
RDX: ffff888030b28000 RSI: ffffffff8a086d46 RDI: 0000000000000005
RBP: ffffc900000074e0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff88805c9e70df
R13: ffff88805c9e70c8 R14: 1ffff92000000e8a R15: ffff8880328cb000
FS:  0000000000000000(0000) GS:ffff888124a0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb1fe602e80 CR3: 000000007a0e4000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 lock_is_held include/linux/lockdep.h:249 [inline]
 lockdep_rtnl_is_held+0xa/0x40 net/core/rtnetlink.c:182
 __in6_dev_get include/net/addrconf.h:347 [inline]
 ip6_ignore_linkdown include/net/addrconf.h:443 [inline]
 find_match+0x34b/0x15d0 net/ipv6/route.c:780
 __find_rr_leaf+0x140/0xe00 net/ipv6/route.c:868
 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 net/ipv6/ip6_input.c:77 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ipv6_rcv+0x1e8/0x650 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
 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_dat_purge.part.0+0x279/0x3a0 net/batman-adv/distributed-arp-table.c:185
 __batadv_dat_purge net/batman-adv/distributed-arp-table.c:166 [inline]
 batadv_dat_purge+0x4b/0xa0 net/batman-adv/distributed-arp-table.c:204
 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: 8485 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 veth0_to_bridge with own address as source address (addr:02:30:c6:0b:32:19, 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 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:02:30:c6:0b:32:19, 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 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:02:30:c6:0b:32:19, vlan:0)
net_ratelimit: 8370 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 veth0_to_bridge with own address as source address (addr:02:30:c6:0b:32:19, 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 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:02:30:c6:0b:32:19, 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 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:02:30:c6:0b:32:19, vlan:0)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/24 10:29 upstream ac3fd01e4c1e bf6fe8fe .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_fdatasync
* Struck through repros no longer work on HEAD.