WARNING in udp_v6_send_skb

Status: upstream: reported on 2026/07/30 00:10
Subsystems: net
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+ce13c07d96d04716eaa2@syzkaller.appspotmail.com
First crash: 5d06h, last: 3d18h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
8cbcb09d repro 💥 WARNING in udp_v6_send_skb 2026/07/30 09:10 2026/07/30 09:10 2026/07/30 09:44 2377cd3d
tool reproduce-crash failed: error: failed to collect 3 valid runs within 6 total attempts. Last infra error: failed to read coverage file /tmp/syz-cover-1785404632654909573_prog1.0 in VM: failed to r...
truncated to first 200 bytes; open job for full error
9402638d assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in udp_v6_send_skb 2026/07/27 00:00 2026/07/27 00:00 2026/07/27 00:52 492bab15

			
		
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] WARNING in udp_v6_send_skb 2 (3) 2026/07/30 14:10

Sample crash report:
------------[ cut here ]------------
len >= 65536u
WARNING: ./include/linux/udp.h:49 at udp_set_len_short include/linux/udp.h:49 [inline], CPU#0: syz.4.4430/24120
WARNING: ./include/linux/udp.h:49 at udp_v6_send_skb+0xd3b/0x13a0 net/ipv6/udp.c:1375, CPU#0: syz.4.4430/24120
Modules linked in:
CPU: 0 UID: 0 PID: 24120 Comm: syz.4.4430 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:udp_set_len_short include/linux/udp.h:49 [inline]
RIP: 0010:udp_v6_send_skb+0xd3b/0x13a0 net/ipv6/udp.c:1375
Code: 42 0f b6 04 38 84 c0 0f 85 37 06 00 00 41 0f b7 1e e9 60 f3 ff ff e8 04 c3 43 f7 90 0f 0b 90 e9 02 f4 ff ff e8 f6 c2 43 f7 90 <0f> 0b 90 e9 e9 f4 ff ff e8 e8 c2 43 f7 90 0f 0b 90 e9 94 f5 ff ff
RSP: 0018:ffffc9000e0a74c8 EFLAGS: 00010287
RAX: ffffffff8a833e8a RBX: ffff8880355e4a00 RCX: 0000000000080000
RDX: ffffc900100ca000 RSI: 00000000000049e3 RDI: 00000000000049e4
RBP: 000000000000244c R08: ffff888049ed5d00 R09: 0000000000000003
R10: 000000000000000b R11: 0000000000000002 R12: dffffc0000000000
R13: ffff888027cb0c80 R14: 0000000000010000 R15: ffff8880355e4a02
FS:  00007f2d4a07b6c0(0000) GS:ffff888124f54000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 0000000029d28000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 udp_v6_push_pending_frames+0xa2/0x140 net/ipv6/udp.c:1451
 udpv6_sendmsg+0xfa0/0x2610 net/ipv6/udp.c:1740
 sock_sendmsg_nosec+0x90/0x180 net/socket.c:775
 __sock_sendmsg net/socket.c:790 [inline]
 ____sys_sendmsg+0x54e/0x850 net/socket.c:2684
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2738
 __sys_sendmmsg+0x273/0x4d0 net/socket.c:2827
 __do_sys_sendmmsg net/socket.c:2854 [inline]
 __se_sys_sendmmsg net/socket.c:2851 [inline]
 __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2851
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2d4919de99
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:00007f2d4a07b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f2d49425fa0 RCX: 00007f2d4919de99
RDX: 0000000000000001 RSI: 0000200000006780 RDI: 0000000000000019
RBP: 00007f2d49233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2d49426038 R14: 00007f2d49425fa0 R15: 00007ffdc2399288
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/27 04:10 net-next 04026c998c24 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce WARNING in udp_v6_send_skb
2026/07/25 16:03 net-next 04026c998c24 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce WARNING in udp_v6_send_skb
* Struck through repros no longer work on HEAD.