syzbot


INFO: rcu detected stall in __unix_dgram_recvmsg

Status: upstream: reported on 2025/07/03 10:08
Reported-by: syzbot+c7179bc6a35fd11c39b9@syzkaller.appspotmail.com
First crash: 57d, last: 15d
Similar bugs (3)
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 813d 881d 0/29 auto-obsoleted due to no activity on 2023/09/05 23:13
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (3) net 1 1 607d 607d 0/29 closed as invalid on 2024/02/12 15:20
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (2) net 1 2 715d 718d 0/29 auto-obsoleted due to no activity on 2023/12/13 22:00

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=3fcc/1/0x4000000000000000 softirq=72451/72451 fqs=1
rcu: 	(detected by 1, t=10503 jiffies, g=90185, q=195 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 16986 Comm: syz.6.3527 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:lockdep_recursion_inc kernel/locking/lockdep.c:462 [inline]
RIP: 0010:lock_acquire+0x151/0x410 kernel/locking/lockdep.c:5753
Code: 01 00 00 41 83 3e 00 0f 85 01 01 00 00 48 c7 84 24 a0 00 00 00 00 00 00 00 9c 8f 84 24 a0 00 00 00 4c 8b b4 24 a0 00 00 00 fa <48> c7 c7 20 c7 aa 8a e8 53 25 06 09 65 ff 05 74 80 9b 7e 45 31 c9
RSP: 0018:ffffc90000007b80 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 45dca8ad4f333800
RDX: 0000000000000000 RSI: ffffffff8afc6760 RDI: ffffffff8afc6720
RBP: ffffc90000007c88 R08: ffffffff8e4a84ef R09: 1ffffffff1c9509d
R10: dffffc0000000000 R11: fffffbfff1c9509e R12: 1ffff92000000f7c
R13: ffff8880b8e2b958 R14: 0000000000000046 R15: dffffc0000000000
FS:  00007f589c8816c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe23a7f5d98 CR3: 000000004bec5000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0xa3/0xe0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1759 [inline]
 __hrtimer_run_queues+0x5e3/0xc40 kernel/time/hrtimer.c:1819
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1881
 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:lock_acquire+0x1f2/0x410 kernel/locking/lockdep.c:5758
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 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 66 43 c7 44 3c 09 00 00 43 c6 44 3c 0b 00
RSP: 0018:ffffc9000f8df480 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 45dca8ad4f333800
RDX: 0000000000000000 RSI: ffffffff8aaacbc0 RDI: ffffffff8afc6780
RBP: ffffc9000f8df588 R08: dffffc0000000000 R09: 1ffffffff21b46b9
R10: dffffc0000000000 R11: fffffbfff21b46ba R12: 1ffff92001f1be9c
R13: ffff888030b50590 R14: 0000000000000246 R15: dffffc0000000000
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
 __unix_dgram_recvmsg+0x1e3/0xd60 net/unix/af_unix.c:2407
 sock_recvmsg_nosec+0x82/0xd0 net/socket.c:1046
 ____sys_recvmsg+0x49b/0x5b0 net/socket.c:2812
 ___sys_recvmsg+0x1b6/0x510 net/socket.c:2856
 do_recvmmsg+0x360/0x7d0 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+0x191/0x240 net/socket.c:3045
 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: 0033:0x7f589b98ebe9
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:00007f589c881038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f589bbb6090 RCX: 00007f589b98ebe9
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007f589ba11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f589bbb6128 R14: 00007f589bbb6090 R15: 00007fffde302798
 </TASK>
rcu: rcu_preempt kthread starved for 10501 jiffies! g90185 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:27304 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 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:
CPU: 1 PID: 16992 Comm: syz.1.3532 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xddf/0x1130 kernel/smp.c:855
Code: 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 da d6 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 15 d3 0a 00 eb 38 f3 90 <42> 0f b6 04 2b 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 f9 d2
RSP: 0018:ffffc9000f7c7900 EFLAGS: 00000293
RAX: ffffffff817ac297 RBX: 1ffff110171c87d9 RCX: ffff888029c69e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000f7c7a80 R08: ffffffff90da3527 R09: 1ffffffff21b46a4
R10: dffffc0000000000 R11: fffffbfff21b46a5 R12: ffff8880b8e43ec8
R13: dffffc0000000000 R14: ffff8880b8f3d588 R15: 0000000000000000
FS:  000055559103f500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3eec29 CR3: 000000002ef54000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1023
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
 text_poke_bp_batch+0x318/0x930 arch/x86/kernel/alternative.c:2432
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_disable_cpuslocked+0xc5/0x1a0 kernel/jump_label.c:237
 static_key_disable+0x1a/0x20 kernel/jump_label.c:245
 tracepoint_remove_func kernel/tracepoint.c:417 [inline]
 tracepoint_probe_unregister+0x6ad/0x930 kernel/tracepoint.c:551
 bpf_raw_tp_link_release+0x63/0x90 kernel/bpf/syscall.c:3369
 bpf_link_free+0x131/0x310 kernel/bpf/syscall.c:2912
 bpf_link_put_direct kernel/bpf/syscall.c:2952 [inline]
 bpf_link_release+0x6e/0x80 kernel/bpf/syscall.c:2959
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdf1358ebe9
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:00007ffc84308108 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00000000000fff58 RCX: 00007fdf1358ebe9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fdf137b7da0 R08: 0000000000000001 R09: 00000004843083ff
R10: 0000001b33c20000 R11: 0000000000000246 R12: 00007fdf137b5fac
R13: 00007fdf137b5fa0 R14: ffffffffffffffff R15: 00007ffc84308220
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/14 21:32 linux-6.6.y 3a8ababb8b6a 5d8c2ac2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2025/07/19 00:45 linux-6.6.y d96eb99e2f0e 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2025/07/03 10:07 linux-6.6.y 3f5b4c104b7d 115ceea7 .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.