syzbot


INFO: rcu detected stall in __unix_dgram_recvmsg (2)

Status: upstream: reported on 2026/04/17 08:34
Reported-by: syzbot+d01746b561934d3e1617@syzkaller.appspotmail.com
First crash: 73d, last: 13h11m
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in __unix_dgram_recvmsg net 1 3 1118d 1185d 0/29 auto-obsoleted due to no activity on 2023/09/05 23:13
linux-6.6 INFO: rcu detected stall in __unix_dgram_recvmsg 1 6 192d 361d 0/2 auto-obsoleted due to no activity on 2026/03/30 01:03
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (3) net 1 1 911d 911d 0/29 closed as invalid on 2024/02/12 15:20
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (2) net 1 2 1019d 1023d 0/29 auto-obsoleted due to no activity on 2023/12/13 22:00

Sample crash report:
ip6_tunnel: ip6gre1 xmit: Local address not yet configured!
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=9964/1/0x4000000000000000 softirq=98837/98839 fqs=0
rcu: 	(detected by 0, t=10502 jiffies, g=140073, q=45 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 22501 Comm: syz.1.4668 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline]
RIP: 0010:do_raw_spin_lock+0x79/0x2b0 kernel/locking/spinlock_debug.c:114
Code: 55 69 81 4c 8d 64 24 20 49 c1 ec 03 48 b8 f1 f1 f1 f1 f8 f3 f3 f3 4b 89 04 2c 4c 8d 77 04 4c 89 f0 48 c1 e8 03 42 0f b6 04 28 <84> c0 0f 85 c3 01 00 00 41 8b 06 3d ad 4e ad de 0f 85 14 01 00 00
RSP: 0018:ffffc900001f0c00 EFLAGS: 00000807
RAX: 0000000000000000 RBX: ffff8880b8f2b740 RCX: 7c0d11e4bf60aa00
RDX: 0000000000000000 RSI: ffffffff8acadce0 RDI: ffff8880b8f2b740
RBP: ffffc900001f0cb0 R08: dffffc0000000000 R09: 1ffffffff22378a1
R10: dffffc0000000000 R11: fffffbfff22378a2 R12: 1ffff9200003e184
R13: dffffc0000000000 R14: ffff8880b8f2b744 R15: dffffc0000000000
FS:  00007fc5455966c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000008b030 CR3: 00000000673f4000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:120 [inline]
 _raw_spin_lock_irq+0xbb/0xf0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1758 [inline]
 __hrtimer_run_queues+0x5da/0xc10 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x39d/0x980 kernel/time/hrtimer.c:1880
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/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:__skb_try_recv_datagram+0xe2/0x4e0 net/core/datagram.c:-1
Code: 44 24 08 31 c0 8b 74 24 04 83 e6 40 48 c7 c1 20 f7 70 88 48 0f 45 c8 48 89 4c 24 50 31 ff e8 05 56 12 f9 49 8d 8f f5 03 00 00 <49> 8d 97 f6 03 00 00 48 8d 73 08 48 89 6c 24 18 48 c1 ed 03 48 89
RSP: 0018:ffffc900056e7648 EFLAGS: 00000297
RAX: ffffffff887492fb RBX: ffff88805ab409b8 RCX: ffff88805ab40bf5
RDX: ffff888028c38000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88805ab40a30 R08: ffffc900056e7830 R09: ffffc900056e77e0
R10: dffffc0000000000 R11: fffffbfff1d15cbe R12: dffffc0000000000
R13: ffff88805ab409d0 R14: ffffc900056e77e0 R15: ffff88805ab40800
 __unix_dgram_recvmsg+0x2f9/0xd90 net/unix/af_unix.c:2412
 sock_recvmsg_nosec+0x82/0xd0 net/socket.c:1047
 ____sys_recvmsg+0x4d7/0x5d0 net/socket.c:2812
 ___sys_recvmsg+0x214/0x590 net/socket.c:2856
 do_recvmmsg+0x377/0x810 net/socket.c:2950
 __sys_recvmmsg net/socket.c:3029 [inline]
 __do_sys_recvmmsg net/socket.c:3052 [inline]
 __se_sys_recvmmsg net/socket.c:3045 [inline]
 __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3045
 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: 0033:0x7fc54479ce59
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:00007fc545596028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fc544a16270 RCX: 00007fc54479ce59
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007fc544832e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc544a16308 R14: 00007fc544a16270 R15: 00007ffff9607388
 </TASK>
rcu: rcu_preempt kthread starved for 10502 jiffies! g140073 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:27656 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:
CPU: 0 PID: 22504 Comm: syz.3.4670 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xd85/0x1190 kernel/smp.c:855
Code: 45 8b 34 24 44 89 f6 83 e6 01 31 ff e8 34 f1 0a 00 41 83 e6 01 49 be 00 00 00 00 00 fc ff df 75 07 e8 6f ed 0a 00 eb 38 f3 90 <42> 0f b6 04 33 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 53 ed
RSP: 0018:ffffc90005407a80 EFLAGS: 00000246
RAX: ffffffff817bf7fd RBX: 1ffff110171e82bd RCX: 0000000000080000
RDX: ffffc9000d57b000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc90005407bf0 R08: ffffffff8e8ae5ef R09: 1ffffffff1d15cbd
R10: dffffc0000000000 R11: fffffbfff1d15cbe R12: ffff8880b8f415e8
R13: ffff8880b8e3d3c0 R14: dffffc0000000000 R15: 0000000000000001
FS:  00007f599ddf66c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c312ab2 CR3: 0000000021d3d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 000000000000000c DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 clock_was_set+0x756/0x800 kernel/time/hrtimer.c:990
 do_settimeofday64+0x59b/0x750 kernel/time/timekeeping.c:1345
 __do_sys_clock_settime kernel/time/posix-timers.c:1130 [inline]
 __se_sys_clock_settime kernel/time/posix-timers.c:1114 [inline]
 __x64_sys_clock_settime+0x25e/0x2a0 kernel/time/posix-timers.c:1114
 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: 0033:0x7f599fb9ce59
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:00007f599ddf6028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007f599fe15fa0 RCX: 00007f599fb9ce59
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007f599fc32e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f599fe16038 R14: 00007f599fe15fa0 R15: 00007ffcd5fc8708
 </TASK>

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/29 15:23 linux-6.6.y d1cfde2d5d15 6a0c72dc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/26 19:32 linux-6.6.y d1cfde2d5d15 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/24 18:19 linux-6.6.y d1cfde2d5d15 302586aa .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/18 18:54 linux-6.6.y 924b4a879cbb a776b0d0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/05/07 21:55 linux-6.6.y 258cf62a6dfd cbf9e0fc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/04/20 23:46 linux-6.6.y 9760bf04666d e65da4ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/04/17 08:33 linux-6.6.y 8cee53b8eaeb de0a551d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
* Struck through repros no longer work on HEAD.