INFO: rcu detected stall in vfs_fallocate

Status: upstream: reported on 2026/07/04 08:45
Reported-by: syzbot+f66c0a164faccd9642e6@syzkaller.appspotmail.com
First crash: 38d, last: 38d
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in vfs_fallocate (4) ext4 1 1 781d 781d 0/29 auto-obsoleted due to no activity on 2024/09/20 02:24
upstream INFO: rcu detected stall in vfs_fallocate ext4 1 6 1804d 1832d 0/29 auto-closed as invalid on 2021/12/01 16:15
linux-4.19 INFO: rcu detected stall in vfs_fallocate 1 1 1481d 1481d 0/1 auto-obsoleted due to no activity on 2022/11/19 13:27
upstream INFO: rcu detected stall in vfs_fallocate (3) ext4 1 1 997d 997d 0/29 auto-obsoleted due to no activity on 2024/02/16 23:28
upstream INFO: rcu detected stall in vfs_fallocate (2) ext4 1 1 1674d 1674d 0/29 closed as invalid on 2022/02/08 10:00
linux-5.15 INFO: rcu detected stall in vfs_fallocate 1 1 679d 679d 0/3 auto-obsoleted due to no activity on 2025/01/09 21:31
upstream INFO: rcu detected stall in vfs_fallocate (5) mm 1 1 681d 681d 0/29 auto-obsoleted due to no activity on 2024/12/28 21:50
linux-4.19 BUG: soft lockup in vfs_fallocate 1 1 1913d 1913d 0/1 auto-closed as invalid on 2021/09/13 17:50
android-5-15 BUG: soft lockup in vfs_fallocate 1 4 765d 806d 0/2 auto-obsoleted due to no activity on 2024/10/05 14:54

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10418 ticks this GP) idle=69f4/1/0x4000000000000000 softirq=34900/34900 fqs=42
rcu: 	(t=10500 jiffies g=46285 q=294 ncpus=2)
rcu: rcu_preempt kthread starved for 10408 jiffies! g46285 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:26920 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 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: 11425 Comm: syz.1.2037 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:434 [inline]
RIP: 0010:__pv_queued_spin_lock_slowpath+0x52e/0x9c0 kernel/locking/qspinlock.c:511
Code: 8b 44 24 18 c6 00 00 48 8b 44 24 10 42 0f b6 04 28 84 c0 0f 85 1b 01 00 00 48 8d 43 01 c6 00 01 41 bc 00 80 ff ff eb 07 f3 90 <41> ff c4 74 47 43 0f b6 04 2e 84 c0 75 2b 80 3b 00 75 eb 48 89 df
RSP: 0018:ffffc900000079a0 EFLAGS: 00000206
RAX: 0000000000000000 RBX: ffff88802dfd8098 RCX: ffff88802b9a0000
RDX: 0000000000000100 RSI: ffffffff8acacb60 RDI: ffffffff8b1cf820
RBP: ffffc90000007a90 R08: ffffffff911e75c7 R09: 1ffffffff223ceb8
R10: dffffc0000000000 R11: fffffbfff223ceb9 R12: 00000000fffff075
R13: dffffc0000000000 R14: 1ffff11005bfb013 R15: ffff8880b8e30001
FS:  00007f5339bf66c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000023ab5000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:586 [inline]
 queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
 queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
 do_raw_spin_lock+0x23e/0x2b0 kernel/locking/spinlock_debug.c:115
 spin_lock include/linux/spinlock.h:351 [inline]
 tcp_write_timer+0x2d/0x280 net/ipv4/tcp_timer.c:707
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x570/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 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:console_flush_all+0x883/0xcf0 arch/x86/include/asm/irqflags.h:-1
Code: ed 01 00 00 e8 8e 74 1b 00 4d 85 ff 48 8b 5c 24 38 75 07 e8 7f 74 1b 00 eb 06 e8 78 74 1b 00 fb 49 bf 00 00 00 00 00 fc ff df <48> 8b 44 24 58 42 0f b6 04 38 84 c0 0f 85 2f 02 00 00 80 3b 01 0f
RSP: 0018:ffffc9000c9aed40 EFLAGS: 00000293
RAX: ffffffff816b70d8 RBX: ffffc9000c9aeebf RCX: ffff88802b9a0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000c9aee90 R08: ffffffff911e7507 R09: 1ffffffff223cea0
R10: dffffc0000000000 R11: fffffbfff223cea1 R12: ffffffff8d8cd3a0
R13: 1ffffffff19f96d8 R14: ffffffff8d8cd3f8 R15: dffffc0000000000
 console_unlock+0xad/0x350 kernel/printk/printk.c:3069
 vprintk_emit+0x497/0x610 kernel/printk/printk.c:2341
 _printk+0xde/0x130 kernel/printk/printk.c:2366
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail_ex+0x375/0x4c0 lib/fault-inject.c:153
 prepare_alloc_pages+0x1e1/0x5b0 mm/page_alloc.c:4273
 __alloc_pages+0x134/0x460 mm/page_alloc.c:4490
 __folio_alloc+0x10/0x20 mm/page_alloc.c:4533
 vma_alloc_folio+0x474/0x8f0 mm/mempolicy.c:2240
 shmem_alloc_folio+0x1a9/0x2a0 mm/shmem.c:1679
 shmem_alloc_and_acct_folio+0x1cb/0x6c0 mm/shmem.c:1704
 shmem_get_folio_gfp+0xe1d/0x2b40 mm/shmem.c:2041
 shmem_get_folio mm/shmem.c:2164 [inline]
 shmem_fallocate+0x8a8/0xfa0 mm/shmem.c:3141
 vfs_fallocate+0x585/0x6f0 fs/open.c:324
 ioctl_preallocate fs/ioctl.c:291 [inline]
 file_ioctl fs/ioctl.c:331 [inline]
 do_vfs_ioctl+0x19ef/0x1cc0 fs/ioctl.c:850
 __do_sys_ioctl fs/ioctl.c:869 [inline]
 __se_sys_ioctl+0x83/0x170 fs/ioctl.c:857
 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: 0033:0x7f533b99de59
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:00007f5339bf6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f533bc26090 RCX: 00007f533b99de59
RDX: 0000200000000040 RSI: 000000004030582a RDI: 0000000000000006
RBP: 00007f5339bf6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007f533bc26128 R14: 00007f533bc26090 R15: 00007fff054dc638
 </TASK>
CPU: 1 PID: 11414 Comm: syz.0.2035 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:seqcount_lockdep_reader_access+0x19a/0x1d0 include/linux/seqlock.h:105
Code: 00 4d 85 e4 75 16 e8 a5 bf 0f 00 eb 15 e8 9e bf 0f 00 e8 89 72 14 09 4d 85 e4 74 ea e8 8f bf 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 43 c7 44 3e 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900001ef3c0 EFLAGS: 00000246
RAX: ffffffff817725c1 RBX: 0000000000000000 RCX: ffff888021575a00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900001ef478 R08: ffffffff911e75c7 R09: 1ffffffff223ceb8
R10: dffffc0000000000 R11: fffffbfff223ceb9 R12: 0000000000000200
R13: 000001fb70472bf8 R14: 1ffff9200003de78 R15: dffffc0000000000
FS:  00007fc494b8c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000000 CR3: 000000005db0d000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 ktime_get_with_offset+0x94/0x330 kernel/time/timekeeping.c:889
 ktime_get_real include/linux/timekeeping.h:79 [inline]
 net_timestamp_set net/core/dev.c:2207 [inline]
 dev_queue_xmit_nit+0x8c9/0xba0 net/core/dev.c:2357
 xmit_one net/core/dev.c:3640 [inline]
 dev_hard_start_xmit+0x150/0x790 net/core/dev.c:3660
 sch_direct_xmit+0x251/0x4a0 net/sched/sch_generic.c:345
 __dev_xmit_skb net/core/dev.c:3881 [inline]
 __dev_queue_xmit+0x162a/0x3630 net/core/dev.c:4416
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 neigh_hh_output include/net/neighbour.h:527 [inline]
 neigh_output include/net/neighbour.h:541 [inline]
 ip_finish_output2+0xd4f/0x1260 net/ipv4/ip_output.c:235
 NF_HOOK_COND include/linux/netfilter.h:293 [inline]
 ip_output+0x2a5/0x3a0 net/ipv4/ip_output.c:436
 dst_output include/net/dst.h:467 [inline]
 ip_local_out net/ipv4/ip_output.c:129 [inline]
 __ip_queue_xmit+0x1056/0x1960 net/ipv4/ip_output.c:540
 __tcp_transmit_skb+0x1dd6/0x3470 net/ipv4/tcp_output.c:1427
 tcp_transmit_skb net/ipv4/tcp_output.c:1445 [inline]
 tcp_write_xmit+0x1550/0x66f0 net/ipv4/tcp_output.c:2784
 __tcp_push_pending_frames+0x96/0x330 net/ipv4/tcp_output.c:2969
 tcp_push_pending_frames include/net/tcp.h:2012 [inline]
 tcp_data_snd_check net/ipv4/tcp_input.c:5658 [inline]
 tcp_rcv_established+0xfc5/0x1d70 net/ipv4/tcp_input.c:6092
 tcp_v4_do_rcv+0x6d3/0xba0 net/ipv4/tcp_ipv4.c:1735
 tcp_v4_rcv+0x2358/0x2a60 net/ipv4/tcp_ipv4.c:2167
 ip_protocol_deliver_rcu+0x20a/0x3f0 net/ipv4/ip_input.c:205
 ip_local_deliver_finish+0x2c3/0x510 net/ipv4/ip_input.c:233
 NF_HOOK+0x32d/0x3b0 include/linux/netfilter.h:304
 dst_input include/net/dst.h:477 [inline]
 ip_sublist_rcv_finish net/ipv4/ip_input.c:580 [inline]
 ip_list_rcv_finish net/ipv4/ip_input.c:631 [inline]
 ip_sublist_rcv+0xa36/0xd60 net/ipv4/ip_input.c:639
 ip_list_rcv+0x3ed/0x440 net/ipv4/ip_input.c:674
 __netif_receive_skb_list_ptype net/core/dev.c:5689 [inline]
 __netif_receive_skb_list_core+0x582/0x770 net/core/dev.c:5737
 __netif_receive_skb_list net/core/dev.c:5789 [inline]
 netif_receive_skb_list_internal+0x943/0xca0 net/core/dev.c:5880
 gro_normal_list include/net/gro.h:451 [inline]
 napi_complete_done+0x329/0x820 net/core/dev.c:6220
 virtqueue_napi_complete drivers/net/virtio_net.c:450 [inline]
 virtnet_poll+0xaa0/0x11e0 drivers/net/virtio_net.c:2236
 __napi_poll+0xbb/0x460 net/core/dev.c:6650
 napi_poll net/core/dev.c:6717 [inline]
 net_rx_action+0x65f/0xcc0 net/core/dev.c:6853
 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:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc9000c957920 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0985008783562800
RDX: 0000000000000000 RSI: ffffffff8acadce0 RDI: ffffffff8b1cf820
RBP: ffffc9000c957a40 R08: dffffc0000000000 R09: 1ffffffff223cebb
R10: dffffc0000000000 R11: fffffbfff223cebc R12: 1ffff9200192af30
R13: ffffc90000a2e420 R14: 0000000000000246 R15: dffffc0000000000
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 futex_q_lock+0x1aa/0x250 kernel/futex/core.c:542
 futex_wait_setup+0xed/0x270 kernel/futex/waitwake.c:607
 futex_wait+0x1bc/0x5c0 kernel/futex/waitwake.c:651
 do_futex+0x2ff/0x3e0 kernel/futex/syscalls.c:134
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x3a9/0x440 kernel/futex/syscalls.c:192
 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: 0033:0x7fc493d9de59
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:00007fc494b8c0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007fc494025fa8 RCX: 00007fc493d9de59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fc494025fa8
RBP: 00007fc494025fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc494026038 R14: 00007fff01a683c0 R15: 00007fff01a684a8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/04 08:45 linux-6.6.y d1cfde2d5d15 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in vfs_fallocate
* Struck through repros no longer work on HEAD.