INFO: rcu detected stall in sock_write_iter (3)

Status: upstream: reported on 2026/05/26 07:14
Reported-by: syzbot+404e8ee8fef0d60fa417@syzkaller.appspotmail.com
First crash: 135d, last: 9d08h
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sock_write_iter (4) origin:lts-only 1 syz done 12 53d 571d 0/3 upstream: reported syz repro on 2025/03/16 07:14
linux-6.6 INFO: rcu detected stall in sock_write_iter origin:upstream missing-backport 1 syz, C inconclusive 13 15d 400d 0/2 upstream: reported C repro on 2025/09/03 11:54
upstream INFO: rcu detected stall in sock_write_iter mm 1 1 2501d 2501d 0/29 closed as invalid on 2019/12/04 14:04
linux-5.15 INFO: rcu detected stall in sock_write_iter (3) 1 1 716d 716d 0/3 auto-obsoleted due to no activity on 2025/01/31 00:48
upstream INFO: rcu detected stall in sock_write_iter (3) net prio:low 1 syz, C done error 222 4d21h 884d 0/29 upstream: reported C repro on 2024/05/07 12:14
linux-5.15 INFO: rcu detected stall in sock_write_iter 1 1 1085d 1085d 0/3 auto-obsoleted due to no activity on 2024/01/28 05:21
linux-5.15 INFO: rcu detected stall in sock_write_iter (2) 1 1 902d 902d 0/3 auto-obsoleted due to no activity on 2024/07/28 08:46
linux-6.1 INFO: rcu detected stall in sock_write_iter 1 1 917d 917d 0/3 auto-obsoleted due to no activity on 2024/07/13 13:13
upstream INFO: rcu detected stall in sock_write_iter (2) netfilter 1 1 1070d 1070d 0/29 auto-obsoleted due to no activity on 2024/01/03 00:51
linux-6.1 INFO: rcu detected stall in sock_write_iter (2) 1 2 263d 327d 0/3 auto-obsoleted due to no activity on 2026/04/29 05:14
android-5-10 BUG: soft lockup in sock_write_iter 1 1 575d 575d 0/2 auto-obsoleted due to no activity on 2025/06/10 11:55
android-5-15 BUG: soft lockup in sock_write_iter 1 24 786d 922d 0/2 auto-obsoleted due to no activity on 2024/11/03 03:04

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2690 jiffies s: 18721 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: 7319 Comm: syz.1.1032 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:perf_trace_lock_acquire+0x34c/0x3f0 include/trace/events/lock.h:24
Code: 8b 4c 24 60 41 b8 01 00 00 00 4c 89 e7 44 89 ee 48 8b 4c 24 38 6a 00 ff 74 24 20 e8 ee 33 42 00 48 83 c4 10 43 c6 44 3e 08 f8 <43> c6 44 3e 04 f8 48 c7 44 24 40 0e 36 e0 45 4b c7 04 3e 00 00 00
RSP: 0018:ffffc900001dfbe0 EFLAGS: 00000046
RAX: 1ffffd1ffffa9c18 RBX: ffffe8ffffd4e0c0 RCX: 18ba11d68c461200
RDX: 0000000000000000 RSI: ffffffff8adf6880 RDI: ffffffff8adf6840
RBP: ffffc900001dfce0 R08: 0000000000000002 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1c4168e R12: ffffffff8c9f9640
R13: ffffe8ffffd4e0c0 R14: 1ffff9200003bf84 R15: dffffc0000000000
FS:  00007fd5de20c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fb23ffc CR3: 000000001968e000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0x452/0x4a0 kernel/locking/lockdep.c:5649
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 __perf_output_begin kernel/events/ring_buffer.c:163 [inline]
 perf_output_begin_forward+0xc3/0xa70 kernel/events/ring_buffer.c:272
 __perf_event_output kernel/events/core.c:7742 [inline]
 perf_event_output_forward+0x1ad/0x2f0 kernel/events/core.c:7760
 __perf_event_overflow+0x457/0x630 kernel/events/core.c:9506
 perf_swevent_overflow kernel/events/core.c:9589 [inline]
 perf_swevent_event+0x315/0x570 kernel/events/core.c:9640
 perf_tp_event+0x36b/0xc10 kernel/events/core.c:10074
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10042
 perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
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 32 7b 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0660 EFLAGS: 00000206
RAX: 18ba11d68c461200 RBX: 1ffff9200003c0d4 RCX: 18ba11d68c461200
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: ffffffff8adf68a0
RBP: ffffc900001e0760 R08: ffffffff90b0f2ff R09: 1ffffffff2161e5f
R10: dffffc0000000000 R11: fffffbfff2161e60 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3bb00 R15: 0000000000000002
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 ip_route_output_key_hash+0x275/0x330 net/ipv4/route.c:2707
 __ip_route_output_key include/net/route.h:137 [inline]
 ip_route_output_flow+0x26/0x150 net/ipv4/route.c:2936
 ip_route_output_ports include/net/route.h:174 [inline]
 inet_sk_rebuild_header+0x93d/0x1ad0 net/ipv4/af_inet.c:1339
 __tcp_retransmit_skb+0x1d3/0x1450 net/ipv4/tcp_output.c:3241
 tcp_retransmit_skb+0x2e/0x350 net/ipv4/tcp_output.c:3340
 tcp_retransmit_timer+0x154a/0x27c0 net/ipv4/tcp_timer.c:574
 tcp_write_timer+0x126/0x280 net/ipv4/tcp_timer.c:676
 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x291/0x910 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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:240 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x4/0x80 kernel/kcov.c:309
Code: 77 22 89 ff 89 f6 49 ff c0 4c 89 01 48 c7 44 11 08 03 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 48 8b 04 24 <65> 48 8b 15 f4 38 80 7e 65 8b 0d f5 38 80 7e 81 e1 00 01 ff 00 74
RSP: 0018:ffffc900062ff950 EFLAGS: 00000206
RAX: ffffffff81d39138 RBX: ffffffff96ca0390 RCX: 0000000000080000
RDX: ffffc90005969000 RSI: 00000000000000aa RDI: 00000000000000aa
RBP: ffff88823bcf6f65 R08: ffffffff96cdb307 R09: 1ffffffff2d9b660
R10: dffffc0000000000 R11: fffffbfff2d9b661 R12: 1ffffffff2d94080
R13: ffff88823bcf7000 R14: dffffc0000000000 R15: 00000000000000aa
 check_canary_byte mm/kfence/core.c:316 [inline]
 for_each_canary mm/kfence/core.c:352 [inline]
 kfence_guarded_free+0x398/0x7b0 mm/kfence/core.c:501
 do_slab_free mm/slub.c:3641 [inline]
 slab_free mm/slub.c:3688 [inline]
 kmem_cache_free+0x199/0x2a0 mm/slub.c:3709
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x7b5/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ad/0xbd0 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 sock_write_iter+0x2d5/0x3e0 net/socket.c:1144
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x482/0x9a0 fs/read_write.c:584
 ksys_write+0x14d/0x260 fs/read_write.c:637
 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: 0033:0x7fd5dd39e159
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:00007fd5de20c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd5dd625fa0 RCX: 00007fd5dd39e159
RDX: 000000000000fe33 RSI: 0000200000000040 RDI: 000000000000000b
RBP: 00007fd5dd43506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd5dd626038 R14: 00007fd5dd625fa0 R15: 00007fffbad7fb18
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/29 22:16 linux-6.1.y 1a8763b93150 328436b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sock_write_iter
2026/08/09 12:07 linux-6.1.y e4f7d8be268e 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sock_write_iter
2026/07/18 15:13 linux-6.1.y 090666d3cc90 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sock_write_iter
2026/05/26 07:13 linux-6.1.y dcbcab9d7079 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sock_write_iter
* Struck through repros no longer work on HEAD.