syzbot


WARNING in em_nbyte_match

Status: upstream: reported C repro on 2025/12/06 11:53
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+1b33c093b885ba7c41ea@syzkaller.appspotmail.com
First crash: 7d08h, last: 4d17h
Bug presence (2)
Date Name Commit Repro Result
2025/12/09 linux-6.1.y (ToT) 50cbba13faa2 C [report] WARNING in em_nbyte_match
2025/12/09 upstream (ToT) cfd4039213e7 C Didn't crash
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in em_nbyte_match net -1 C done 7 7d08h 22d 26/29 upstream: reported C repro on 2025/11/21 15:29
linux-6.6 WARNING in em_nbyte_match origin:lts-only -1 C 3 6d14h 7d08h 0/2 upstream: reported C repro on 2025/12/06 11:58

Sample crash report:
device syzkaller0 entered promiscuous mode
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4431 at include/linux/skbuff.h:2844 skb_transport_header include/linux/skbuff.h:2844 [inline]
WARNING: CPU: 0 PID: 4431 at include/linux/skbuff.h:2844 tcf_get_base_ptr include/net/pkt_cls.h:529 [inline]
WARNING: CPU: 0 PID: 4431 at include/linux/skbuff.h:2844 em_nbyte_match+0x2cc/0x3e0 net/sched/em_nbyte.c:43
Modules linked in:
CPU: 0 PID: 4431 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:skb_transport_header include/linux/skbuff.h:2844 [inline]
RIP: 0010:tcf_get_base_ptr include/net/pkt_cls.h:529 [inline]
RIP: 0010:em_nbyte_match+0x2cc/0x3e0 net/sched/em_nbyte.c:43
Code: c0 eb 07 e8 86 11 28 f9 31 c0 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 70 11 28 f9 0f 0b e9 e5 fe ff ff e8 64 11 28 f9 <0f> 0b e9 00 fe ff ff 89 d1 80 e1 07 fe c1 38 c1 0f 8c 7a fd ff ff
RSP: 0018:ffffc90003517138 EFLAGS: 00010293
RAX: ffffffff8858c4fc RBX: ffff888029bb8640 RCX: ffff88807a1b3b80
RDX: 0000000000000000 RSI: 000000000000ffff RDI: 000000000000ffff
RBP: 000000000000ffff R08: ffff88807a1b3b80 R09: 0000000000000003
R10: 0000000000000002 R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff110053770de R14: ffff88802ebb8ac8 R15: 1ffff11005d77159
FS:  00005555674f6500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000012c0 CR3: 000000002f425000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 tcf_em_match net/sched/ematch.c:494 [inline]
 __tcf_em_tree_match+0x1a4/0x760 net/sched/ematch.c:520
 tcf_em_tree_match include/net/pkt_cls.h:502 [inline]
 basic_classify+0x111/0x2c0 net/sched/cls_basic.c:48
 __tcf_classify net/sched/cls_api.c:1569 [inline]
 tcf_classify+0x331/0xbf0 net/sched/cls_api.c:1635
 multiq_classify net/sched/sch_multiq.c:39 [inline]
 multiq_enqueue+0xf6/0x480 net/sched/sch_multiq.c:66
 dev_qdisc_enqueue+0x4c/0x2b0 net/core/dev.c:3875
 __dev_xmit_skb net/core/dev.c:3964 [inline]
 __dev_queue_xmit+0xf8e/0x3760 net/core/dev.c:4312
 packet_snd net/packet/af_packet.c:3127 [inline]
 packet_sendmsg+0x3be8/0x4ea0 net/packet/af_packet.c:3158
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x59b/0x970 net/socket.c:2519
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5a7f18f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc8341b138 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f5a7f3e5fa0 RCX: 00007f5a7f18f749
RDX: 0000000000000004 RSI: 00002000000000c0 RDI: 0000000000000007
RBP: 00007f5a7f213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5a7f3e5fa0 R14: 00007f5a7f3e5fa0 R15: 0000000000000003
 </TASK>

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/06 14:05 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan WARNING in em_nbyte_match
2025/12/06 14:30 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in em_nbyte_match
2025/12/06 13:38 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in em_nbyte_match
2025/12/06 12:46 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in em_nbyte_match
2025/12/06 12:16 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan WARNING in em_nbyte_match
2025/12/06 12:14 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan WARNING in em_nbyte_match
2025/12/06 11:55 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in em_nbyte_match
2025/12/06 11:53 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in em_nbyte_match
2025/12/06 11:53 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in em_nbyte_match
* Struck through repros no longer work on HEAD.