syzbot


INFO: rcu detected stall in llc_rcv

Status: upstream: reported on 2026/04/01 08:56
Reported-by: syzbot+df24ecf861bc428033e9@syzkaller.appspotmail.com
First crash: 70d, last: 12d
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in llc_rcv (2) net bpf 1 1 630d 630d 0/29 auto-obsoleted due to no activity on 2024/12/17 08:05
upstream INFO: rcu detected stall in llc_rcv kernel 1 1 747d 747d 0/29 auto-obsoleted due to no activity on 2024/07/23 07:44

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2633 jiffies s: 1201 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4405 Comm: syz.3.14 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__lock_acquire+0xdaf/0x7d10 kernel/locking/lockdep.c:5019
Code: 00 48 c7 c0 40 41 c0 96 48 c1 e8 03 49 b8 00 00 00 00 00 fc ff df 42 0f b6 04 00 84 c0 0f 85 54 5c 00 00 83 3d 11 e0 5b 15 00 <48> 8b 84 24 a8 00 00 00 75 34 48 63 d8 48 89 d8 48 c1 e8 06 48 8d
RSP: 0018:ffffc900001e0020 EFLAGS: 00000046
RAX: 0000000000000004 RBX: ffffffff90488879 RCX: ffffffff96c04103
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90afd248
RBP: ffffc900001e0270 R08: dffffc0000000000 R09: 1ffffffff215fa49
R10: dffffc0000000000 R11: fffffbfff215fa4a R12: ffff88807adc1dc0
R13: 0000000000000008 R14: ffff88807adc28f0 R15: ffff88807adc2910
FS:  00007f4aae4f16c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000031000 CR3: 0000000057be6000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 seqcount_lockdep_reader_access+0xcd/0x1d0 include/linux/seqlock.h:102
 ktime_get+0x31/0x270 kernel/time/timekeeping.c:846
 clockevents_program_event+0xe2/0x310 kernel/time/clockevents.c:326
 hrtimer_interrupt+0x59d/0x9c0 kernel/time/hrtimer.c:1886
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 3f 4e 20 f7 65 8b 05 40 c0 c9 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900001e0720 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 3251d92c8b83b000
RDX: dffffc0000000000 RSI: ffffffff8a8c19a0 RDI: 0000000000000001
RBP: ffffc900001e07a0 R08: ffffffff90afd277 R09: 1ffffffff215fa4e
R10: dffffc0000000000 R11: fffffbfff215fa4f R12: dffffc0000000000
R13: ffff888029357140 R14: ffffffff96e2bc48 R15: 1ffff9200003c0e4
 __debug_check_no_obj_freed lib/debugobjects.c:988 [inline]
 debug_check_no_obj_freed+0x515/0x530 lib/debugobjects.c:1009
 slab_free_hook mm/slub.c:1704 [inline]
 slab_free_freelist_hook+0xd2/0x1a0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free+0xf7/0x290 mm/slub.c:3709
 llc_rcv+0x755/0xc60 net/llc/llc_input.c:-1
 __netif_receive_skb_list_ptype net/core/dev.c:5667 [inline]
 __netif_receive_skb_list_core+0x6e6/0x750 net/core/dev.c:5710
 __netif_receive_skb_list net/core/dev.c:5762 [inline]
 netif_receive_skb_list_internal+0x93f/0xca0 net/core/dev.c:5853
 netif_receive_skb_list+0x51/0x4e0 net/core/dev.c:5905
 ieee80211_rx_napi+0x357/0x3d0 net/mac80211/rx.c:5342
 ieee80211_rx include/net/mac80211.h:4849 [inline]
 ieee80211_handle_queued_frames+0x105/0x1b0 net/mac80211/main.c:317
 tasklet_action_common+0x2fe/0x4d0 kernel/softirq.c:827
 handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5124
Code: 0f 84 3b 01 00 00 48 85 db 0f 85 5a 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 a0 eb de 08 e8 5b 2d 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc90004a27118 EFLAGS: 00000286
RAX: 3251d92c8b83b000 RBX: 0000000000000000 RCX: 3251d92c8b83b000
RDX: dffffc0000000000 RSI: ffffffff8a8c19a0 RDI: ffffffff8adf1b60
RBP: ffffc90004a27170 R08: ffffffff90afd277 R09: 1ffffffff215fa4e
R10: dffffc0000000000 R11: fffffbfff215fa4f R12: ffff88807adc1dc0
R13: dffffc0000000000 R14: ffff88807cd23b80 R15: ffff8880b8f3b5d0
 context_switch kernel/sched/core.c:5248 [inline]
 __schedule+0x11d9/0x40e0 kernel/sched/core.c:6562
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__might_resched+0x1b3/0x630 kernel/sched/core.c:9934
Code: 0c f8 74 45 4c 8d 62 2c 4c 89 e0 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 9a 03 00 00 41 f6 04 24 02 75 26 4c 8d a2 70 0a 00 00 <4c> 89 e0 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 a0 03 00 00 41 83
RSP: 0018:ffffc90004a27480 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 1ffff92000944e98 RCX: 3251d92c8b83b000
RDX: ffff88807adc1dc0 RSI: ffffffff8a8c2b20 RDI: ffffffff8adf1b60
RBP: ffffc90004a27598 R08: dffffc0000000000 R09: 1ffffffff215fa4e
R10: dffffc0000000000 R11: fffffbfff215fa4f R12: ffff88807adc2830
R13: dffffc0000000000 R14: ffff88807adc21fc R15: 1ffff1100f5b843f
 get_mmap_lock_carefully mm/memory.c:5321 [inline]
 lock_mm_and_find_vma+0x61/0x2f0 mm/memory.c:5382
 do_user_addr_fault+0x2db/0xb10 arch/x86/mm/fault.c:1310
 handle_page_fault arch/x86/mm/fault.c:1429 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1482
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0010:copy_user_enhanced_fast_string+0xa/0x40 arch/x86/lib/copy_user_64.S:166
Code: ff c9 75 f2 89 d1 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 31 c0 0f 01 ca c3 8d 0c ca 89 ca eb 20 0f 01 cb 83 fa 40 72 38 89 d1 <f3> a4 31 c0 0f 01 ca c3 89 ca eb 0a 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90004a27788 EFLAGS: 00050206
RAX: ffffffff840f4a01 RBX: 0000000000033fe0 RCX: 0000000000003020
RDX: 0000000000033fe0 RSI: 0000200000031000 RDI: ffffc90004b21fc0
RBP: 0000000000000000 R08: ffffc90004b24fdf R09: 1ffff920009649fb
R10: dffffc0000000000 R11: fffff520009649fc R12: 00007ffffffcb020
R13: 0000000000000000 R14: 0000200000000040 R15: ffffc90004af1000
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_from_user arch/x86/include/asm/uaccess_64.h:52 [inline]
 copyin+0xe7/0x120 lib/iov_iter.c:183
 _copy_from_iter+0x447/0x1130 lib/iov_iter.c:631
 copy_from_iter include/linux/uio.h:187 [inline]
 copy_from_iter_full include/linux/uio.h:194 [inline]
 memcpy_from_msg include/linux/skbuff.h:4076 [inline]
 netlink_sendmsg+0x755/0xbd0 net/netlink/af_netlink.c:1857
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x5be/0x970 net/socket.c:2518
 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2572
 __sys_sendmsg net/socket.c:2601 [inline]
 __do_sys_sendmsg net/socket.c:2610 [inline]
 __se_sys_sendmsg+0x1bb/0x2a0 net/socket.c:2608
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4aad59ce59
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:00007f4aae4f1028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f4aad815fa0 RCX: 00007f4aad59ce59
RDX: 0000000000000000 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007f4aad632d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4aad816038 R14: 00007f4aad815fa0 R15: 00007ffea4f06658
 </TASK>

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/30 01:21 linux-6.1.y dcbcab9d7079 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in llc_rcv
2026/05/19 15:44 linux-6.1.y c27210688955 223544dc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in llc_rcv
2026/04/26 10:58 linux-6.1.y 7c87defbd336 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in llc_rcv
2026/04/01 08:55 linux-6.1.y 1989cd3d56e2 fb8b2c26 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in llc_rcv
2026/04/29 05:40 linux-6.1.y 7c87defbd336 95008c03 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf BUG: soft lockup in llc_rcv
* Struck through repros no longer work on HEAD.