INFO: rcu detected stall in __alloc_skb

Status: upstream: reported on 2026/09/25 10:19
Reported-by: syzbot+91415b9428f909ffe029@syzkaller.appspotmail.com
First crash: 18d, last: 18d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in __alloc_skb net 1 2 2956d 2955d 0/29 closed as invalid on 2018/09/11 09:33
upstream INFO: rcu detected stall in __alloc_skb (2) fs mm 1 3 1631d 1631d 0/29 auto-closed as invalid on 2022/06/24 21:19
upstream INFO: rcu detected stall in __alloc_skb (4) kasan mm 1 1 346d 346d 0/29 auto-obsoleted due to no activity on 2026/01/30 03:22
upstream INFO: rcu detected stall in __alloc_skb (3) net 1 1 1426d 1426d 0/29 auto-obsoleted due to no activity on 2023/01/16 19:06
upstream BUG: soft lockup in __alloc_skb mm 1 1 1277d 1277d 0/29 auto-obsoleted due to no activity on 2023/08/19 06:32

Sample crash report:
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 GPs behind) idle=9ab/1/0x4000000000000002 softirq=99597/99598 fqs=2071 
	(detected by 1, t=10502 jiffies, g=132077, q=1491)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 1596 Comm: syz.8.7892 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:check_kcov_mode kernel/kcov.c:171 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:226 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x13/0x80 kernel/kcov.c:292
Code: 4a 89 7c 02 10 4a 89 74 02 18 4a 89 44 02 20 48 ff c1 48 89 0a c3 90 48 8b 04 24 65 48 8b 0d b4 57 89 7e 65 8b 15 b5 57 89 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 5b 83 b9 34 16 00 00
RSP: 0018:ffffc900000078f8 EFLAGS: 00000046
RAX: ffffffff8180f184 RBX: 0000000000000014 RCX: ffff888020e6bb80
RDX: 0000000000000102 RSI: 0000000000000014 RDI: 0000000000002000
RBP: ffffc90000007a08 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffe8ffffc35e00
R13: ffffffff8c369e60 R14: ffffc90000007980 R15: ffffc900000079a0
FS:  00007f49c86216c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd4326d4ff8 CR3: 000000002fd9f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_trace_buf_alloc+0x24/0x300 kernel/trace/trace_event_perf.c:409
 perf_trace_preemptirq_template+0x180/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 42 0b 9d 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007b00 EFLAGS: 00000206
RAX: 8bfced6cf4f43900 RBX: 1ffff92000000f64 RCX: 8bfced6cf4f43900
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a48c0
RBP: ffffc90000007bd8 R08: ffffffff901f10d7 R09: 1ffffffff203e21a
R10: dffffc0000000000 R11: fffffbfff203e21b R12: ffffffff8c323400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:strlen+0x1b/0x60 lib/string.c:581
Code: e4 4c 89 f7 e8 e6 80 b2 fd eb da 0f 1f 40 00 41 57 41 56 41 54 53 48 c7 c0 ff ff ff ff 49 be 00 00 00 00 00 fc ff df 48 89 fb <49> 89 c7 48 89 d8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 11 48 ff c3
RSP: 0018:ffffc90002dcf3f8 EFLAGS: 00000202
RAX: 000000000000001e RBX: ffffffff8a35733f RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8c3ef560 RDI: ffffffff8a357320
RBP: ffffc90002dcf520 R08: 0000000000000000 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1b163de R12: ffffffff8c3ef560
R13: 1ffff920005b9e8c R14: dffffc0000000000 R15: 000000000000001d
 trace_event_get_offsets_lock_acquire include/trace/events/lock.h:23 [inline]
 perf_trace_lock_acquire+0xc6/0x3f0 include/trace/events/lock.h:13
 trace_lock_acquire include/trace/events/lock.h:13 [inline]
 lock_acquire+0x3d7/0x400 kernel/locking/lockdep.c:5596
 fs_reclaim_acquire+0x91/0x100 mm/page_alloc.c:4597
 might_alloc include/linux/sched/mm.h:206 [inline]
 slab_pre_alloc_hook+0x20/0xc0 mm/slab.h:492
 slab_alloc_node mm/slub.c:3139 [inline]
 kmem_cache_alloc_node+0x47/0x2c0 mm/slub.c:3261
 __alloc_skb+0xf4/0x750 net/core/skbuff.c:415
 alloc_skb include/linux/skbuff.h:1162 [inline]
 netlink_dump+0x1cc/0xdd0 net/netlink/af_netlink.c:2250
 netlink_recvmsg+0x685/0xe50 net/netlink/af_netlink.c:2002
 ____sys_recvmsg+0x2ca/0x5b0 net/socket.c:-1
 ___sys_recvmsg+0x213/0x5c0 net/socket.c:2707
 __sys_recvmsg net/socket.c:2737 [inline]
 __do_sys_recvmsg net/socket.c:2747 [inline]
 __se_sys_recvmsg net/socket.c:2744 [inline]
 __x64_sys_recvmsg+0x201/0x2d0 net/socket.c:2744
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f49ca3c9159
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:00007f49c8621028 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 00007f49ca650fa0 RCX: 00007f49ca3c9159
RDX: 0000000000010000 RSI: 0000200000000340 RDI: 0000000000000003
RBP: 00007f49ca46006b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f49ca651038 R14: 00007f49ca650fa0 R15: 00007ffd8d8c2478
 </TASK>
net_ratelimit: 9480 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
net_ratelimit: 9214 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/25 10:19 linux-5.15.y 0248c33e835e f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __alloc_skb
* Struck through repros no longer work on HEAD.