syzbot
INFO: rcu detected stall in compat_sys_sendmmsg
Status: auto-obsoleted due to no activity on 2026/07/06 16:03
Subsystems:
net
Labels:
prio:high
[Documentation on labels]
First crash: 134d, last: 130d
Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P8317/1:b..l
rcu: (detected by 0, t=10505 jiffies, g=296633, q=448 ncpus=2)
task:syz.6.10512 state:R running task stack:24648 pid:8317 tgid:8316 ppid:5766 task_flags:0x400140 flags:0x08080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0x15dd/0x52d0 kernel/sched/core.c:6911
preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7238
irqentry_exit+0x599/0x620 kernel/entry/common.c:239
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:on_stack arch/x86/include/asm/stacktrace.h:55 [inline]
RIP: 0010:stack_access_ok arch/x86/kernel/unwind_orc.c:409 [inline]
RIP: 0010:deref_stack_reg arch/x86/kernel/unwind_orc.c:419 [inline]
RIP: 0010:unwind_next_frame+0xce5/0x23c0 arch/x86/kernel/unwind_orc.c:600
Code: 03 0f 84 f5 01 00 00 83 fe 02 0f 85 a8 07 00 00 4c 89 7c 24 28 4d 8d 7e 08 4c 89 fd 48 c1 ed 03 48 b8 00 00 00 00 00 fc ff df <80> 7c 05 00 00 74 08 4c 89 ff e8 1c 78 b9 00 4c 89 7c 24 68 48 89
RSP: 0000:ffffc90005d06a18 EFLAGS: 00000a02
RAX: dffffc0000000000 RBX: ffffffff912c4ba3 RCX: ffffffff90837e6c
RDX: ffffffff912c4b9e RSI: 0000000000000002 RDI: ffffffff8c27d4a0
RBP: 1ffff92000ba0d5e R08: 0000000000000003 R09: ffffffff8e75e5a0
R10: ffffc90005d06b38 R11: ffffffff81b0dbf0 R12: ffffc90005d071a0
R13: ffffc90005d06b38 R14: ffffc90005d06ae8 R15: ffffc90005d06af0
arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4538 [inline]
slab_alloc_node mm/slub.c:4866 [inline]
kmem_cache_alloc_node_noprof+0x384/0x690 mm/slub.c:4918
__alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
alloc_skb include/linux/skbuff.h:1383 [inline]
alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6763
sock_alloc_send_pskb+0x878/0x990 net/core/sock.c:2995
sock_alloc_send_skb include/net/sock.h:1894 [inline]
__ip_append_data+0x2bc5/0x3f30 net/ipv4/ip_output.c:1127
ip_make_skb+0x22e/0x450 net/ipv4/ip_output.c:1574
udp_sendmsg+0x19fb/0x22f0 net/ipv4/udp.c:1480
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x80a/0x9f0 net/socket.c:2592
___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
__sys_sendmmsg+0x2e7/0x4e0 net/socket.c:2728
__compat_sys_sendmmsg net/compat.c:360 [inline]
__do_compat_sys_sendmmsg net/compat.c:367 [inline]
__se_compat_sys_sendmmsg net/compat.c:364 [inline]
__ia32_compat_sys_sendmmsg+0xa2/0xc0 net/compat.c:364
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0x20d/0x640 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf70bef6c
RSP: 002b:00000000f54ad50c EFLAGS: 00000206 ORIG_RAX: 0000000000000159
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000080004d00
RDX: 0000000000000300 RSI: 0000000000000f00 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10504 jiffies! g296633 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=1 timer-softirq=114143
rcu: rcu_preempt kthread starved for 10505 jiffies! g296633 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27656 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0x15dd/0x52d0 kernel/sched/core.c:6911
__schedule_loop kernel/sched/core.c:6993 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7008
schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x312/0x11d0 kernel/rcu/tree.c:2095
rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2297
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 8309 Comm: syz.5.10510 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:num_possible_cpus include/linux/cpumask.h:1222 [inline]
RIP: 0010:mm_get_cid kernel/sched/sched.h:3853 [inline]
RIP: 0010:sched_mm_cid_fork+0x5b0/0x1120 kernel/sched/core.c:10679
Code: 00 00 31 ed 31 db e9 7b 01 00 00 49 c7 c4 98 4e 1b 8e 49 c1 ec 03 41 bd 00 00 00 80 eb 0a 89 e8 f7 d8 0f 81 e3 fe ff ff f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 84 c0 75 40 44 8b 35
RSP: 0000:ffffc90005f87c48 EFLAGS: 00000887
RAX: 0000000080000000 RBX: ffff8880284b6150 RCX: 0000000080000001
RDX: dffffc0000000000 RSI: 0000000000000002 RDI: ffff8880284b6150
RBP: 0000000080000000 R08: 1ffff11005096ad9 R09: 0000000000000000
R10: ffff8880284b5814 R11: fffff52000bf0f78 R12: 1ffffffff1c369d3
R13: 0000000080000000 R14: 0000000000000002 R15: ffff8880284b55c0
FS: 0000000000000000(0000) GS:ffff888125554000(0063) knlGS:00000000f53f6b40
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000034e10ff8 CR3: 0000000056778000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 000000000000000e DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bprm_execve+0xda1/0x1460 fs/exec.c:1771
do_execveat_common+0x50d/0x690 fs/exec.c:1846
__do_compat_sys_execveat fs/exec.c:1968 [inline]
__se_compat_sys_execveat fs/exec.c:1961 [inline]
__ia32_compat_sys_execveat+0xcd/0xf0 fs/exec.c:1961
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
do_int80_emulation+0x173/0x4d0 arch/x86/entry/syscall_32.c:172
asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:621
RIP: 0023:0xf7f32f6c
Code: 90 85 d2 74 0a 89 ce 81 e6 ff 0f 00 00 89 32 85 c0 74 05 c1 e9 0c 89 08 31 c0 5e 5d c3 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 58 b8
RSP: 002b:00000000f53f650c EFLAGS: 00000206 ORIG_RAX: 0000000000000166
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000080000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000001000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Struck through repros no longer work on HEAD.