syzbot


WARNING in rcu_note_context_switch (5)

Status: upstream: reported on 2025/12/26 16:54
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+84d4a405ed798b40c96d@syzkaller.appspotmail.com
First crash: 71d, last: 6d19h
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] WARNING in rcu_note_context_switch (5) 0 (1) 2025/12/26 16:54
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in rcu_note_context_switch (4) net -1 1 245d 245d 0/29 closed as invalid on 2025/09/01 08:35
upstream WARNING in rcu_note_context_switch (3) net -1 1 478d 474d 0/29 auto-obsoleted due to no activity on 2025/02/18 17:10
upstream WARNING in rcu_note_context_switch kernel -1 C done 1 2346d 2346d 13/29 fixed on 2019/10/15 23:40
upstream WARNING in rcu_note_context_switch (2) rcu -1 C 13 594d 590d 0/29 auto-obsoleted due to no activity on 2024/09/25 21:55

Sample crash report:
------------[ cut here ]------------
Voluntary context switch within RCU read-side critical section!
WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0xcac/0xf40 kernel/rcu/tree_plugin.h:332, CPU#0: syz.2.2800/16601
Modules linked in:
CPU: 0 UID: 0 PID: 16601 Comm: syz.2.2800 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:rcu_note_context_switch+0xcac/0xf40 kernel/rcu/tree_plugin.h:332
Code: 00 41 c6 45 00 00 48 8b 3d c1 d6 65 0e 48 81 c4 b8 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d e9 4b 63 ff ff 48 8d 3d 24 b4 69 0e <67> 48 0f b9 3a e9 1b f4 ff ff 90 0f 0b 90 45 84 e4 0f 84 ea f3 ff
RSP: 0018:ffffc9000f7b6bf0 EFLAGS: 00010002
RAX: 0000000000000000 RBX: ffff88802896bc80 RCX: 0000000080000002
RDX: 0000000000000000 RSI: ffffffff8c27a860 RDI: ffffffff90150910
RBP: dffffc0000000000 R08: ffffffff90117db7 R09: 1ffffffff2022fb6
R10: dffffc0000000000 R11: fffffbfff2022fb7 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8880b863bd40 R15: ffff88802896c104
FS:  00007f12fc3a66c0(0000) GS:ffff888125466000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c361fae CR3: 0000000040b2e000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 000000000000000c DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __schedule+0x2ff/0x5340 kernel/sched/core.c:6791
 __schedule_loop kernel/sched/core.c:6989 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7004
 netlink_broadcast_filtered+0xfa1/0x1020 net/netlink/af_netlink.c:1547
 nlmsg_multicast_filtered include/net/netlink.h:1165 [inline]
 nlmsg_multicast include/net/netlink.h:1184 [inline]
 nlmsg_notify+0xf0/0x1a0 net/netlink/af_netlink.c:2593
 __ip6_del_rt_siblings+0x5fc/0x7d0 net/ipv6/route.c:4066
 ip6_route_del+0x1047/0x1100 net/ipv6/route.c:4206
 inet6_rtm_delroute+0x5d7/0x6d0 net/ipv6/route.c:5639
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
 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: 0033:0x7f12fb59c629
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:00007f12fc3a6028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f12fb816090 RCX: 00007f12fb59c629
RDX: 0000000000000000 RSI: 0000200000000280 RDI: 000000000000000a
RBP: 00007f12fb632b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f12fb816128 R14: 00007f12fb816090 R15: 00007f12fb93fa48
 </TASK>
----------------
Code disassembly (best guess):
   0:	00 41 c6             	add    %al,-0x3a(%rcx)
   3:	45 00 00             	add    %r8b,(%r8)
   6:	48 8b 3d c1 d6 65 0e 	mov    0xe65d6c1(%rip),%rdi        # 0xe65d6ce
   d:	48 81 c4 b8 00 00 00 	add    $0xb8,%rsp
  14:	5b                   	pop    %rbx
  15:	41 5c                	pop    %r12
  17:	41 5d                	pop    %r13
  19:	41 5e                	pop    %r14
  1b:	41 5f                	pop    %r15
  1d:	5d                   	pop    %rbp
  1e:	e9 4b 63 ff ff       	jmp    0xffff636e
  23:	48 8d 3d 24 b4 69 0e 	lea    0xe69b424(%rip),%rdi        # 0xe69b44e
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 1b f4 ff ff       	jmp    0xfffff44f
  34:	90                   	nop
  35:	0f 0b                	ud2
  37:	90                   	nop
  38:	45 84 e4             	test   %r12b,%r12b
  3b:	0f                   	.byte 0xf
  3c:	84 ea                	test   %ch,%dl
  3e:	f3                   	repz
  3f:	ff                   	.byte 0xff

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/22 18:56 upstream 32a92f8c8932 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in rcu_note_context_switch
2026/02/25 15:34 upstream 7dff99b35460 c162cde9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in rcu_note_context_switch
2025/12/22 16:43 upstream 9448598b22c5 d1b870e1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in rcu_note_context_switch
* Struck through repros no longer work on HEAD.