INFO: rcu detected stall in kcm_sendmsg

Status: auto-obsoleted due to no activity on 2026/07/11 07:25
Subsystems: mm
Labels: prio:high
[Documentation on labels]
First crash: 132d, last: 132d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
45840000 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ INFO: rcu detected stall in kcm_sendmsg 2026/05/21 18:07 2026/05/21 18:07 2026/05/21 19:03 d5742584

Sample crash report:
sched: DL replenish lagged too much
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10558/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=55473, q=877613 ncpus=2)
task:syz.5.1333      state:R  running task     stack:26208 pid:10558 tgid:10546 ppid:9845   task_flags:0x400040 flags:0x00080002
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:__orc_find arch/x86/kernel/unwind_orc.c:103 [inline]
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:238 [inline]
RIP: 0010:unwind_next_frame+0x528/0x23c0 arch/x86/kernel/unwind_orc.c:510
Code: 4c 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 75 27 49 63 07 4c 01 f8 49 8d 4f 04 4c 39 e0 48 0f 46 e9 <49> 8d 47 fc 48 0f 47 d8 4d 0f 46 ef 48 39 dd 76 a2 e9 76 fd ff ff
RSP: 0018:ffffc9000c31ed38 EFLAGS: 00000202
RAX: ffffffff8252f59c RBX: ffffffff90356684 RCX: ffffffff90356670
RDX: ffffffff90356654 RSI: ffffffff90b7286c RDI: ffffffff8c27d520
RBP: ffffffff90356654 R08: 000000000000000d R09: ffffffff8e75e5a0
R10: ffffc9000c31ee58 R11: ffffffff81b0db30 R12: ffffffff8252f580
R13: ffffffff90356654 R14: ffffc9000c31ee08 R15: ffffffff9035666c
 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 save_stack+0x122/0x230 mm/page_owner.c:165
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
 __slab_free+0x263/0x2b0 mm/slub.c:5573
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 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
 kmalloc_reserve net/core/skbuff.c:613 [inline]
 __alloc_skb+0x27d/0x7d0 net/core/skbuff.c:713
 alloc_skb include/linux/skbuff.h:1383 [inline]
 kcm_sendmsg+0x952/0x2b60 net/kcm/kcmsock.c:818
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 sock_sendmsg+0x3fb/0x450 net/socket.c:765
 splice_to_socket+0xae2/0x11f0 fs/splice.c:884
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x101/0x160 fs/splice.c:1159
 splice_direct_to_actor+0x53a/0xc70 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x195/0x290 fs/splice.c:1228
 do_sendfile+0x535/0x7d0 fs/read_write.c:1372
 __do_sys_sendfile64 fs/read_write.c:1433 [inline]
 __se_sys_sendfile64+0x144/0x1a0 fs/read_write.c:1419
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb8c399c819
RSP: 002b:00007fb8c47ff028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fb8c3c16270 RCX: 00007fb8c399c819
RDX: 0000000000000000 RSI: 000000000000000d RDI: 000000000000000c
RBP: 00007fb8c3a32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 000000008000fb00 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb8c3c16308 R14: 00007fb8c3c16270 R15: 00007fb8c3d3fa48
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/12 07:15 upstream e753c16cb3dd 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in kcm_sendmsg
* Struck through repros no longer work on HEAD.