netdev - [syzbot ci] Re: net: sched: refactor qdisc drop reasons into dedicated tracepoint

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Message-ID: <6985a70c.050a0220.3b3015.0034.GAE@google.com>
Date: Fri, 06 Feb 2026 00:32:12 -0800
From: syzbot ci <syzbot+ci335f183b8446659a@...kaller.appspotmail.com>
To: atenart@...hat.com, bpf@...r.kernel.org, carges@...udflare.com, 
	davem@...emloft.net, edumazet@...gle.com, eric.dumazet@...il.com, 
	hawk@...nel.org, horms@...nel.org, jhs@...atatu.com, jiri@...nulli.us, 
	kernel-team@...udflare.com, kuba@...nel.org, netdev@...r.kernel.org, 
	pabeni@...hat.com, toke@...e.dk, xiyou.wangcong@...il.com
Cc: syzbot@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: [syzbot ci] Re: net: sched: refactor qdisc drop reasons into
 dedicated tracepoint

syzbot ci has tested the following series

[v2] net: sched: refactor qdisc drop reasons into dedicated tracepoint
https://lore.kernel.org/all/177032644012.1975497.16411100029657607833.stgit@firesoul
* [PATCH net-next v2 1/6] net: sched: introduce qdisc-specific drop reason tracing
* [PATCH net-next v2 2/6] net: sched: sfq: convert to qdisc drop reasons
* [PATCH net-next v2 3/6] net: sched: sch_cake: use enum qdisc_drop_reason for cobalt_should_drop
* [PATCH net-next v2 4/6] net: sched: rename QDISC_DROP_CAKE_FLOOD to QDISC_DROP_FLOOD_PROTECTION
* [PATCH net-next v2 5/6] net: sched: rename QDISC_DROP_FQ_* to generic names
* [PATCH net-next v2 6/6] net: sched: sch_dualpi2: use qdisc_dequeue_drop() for dequeue drops

and found the following issue:
WARNING in __dev_queue_xmit

Full report is available here:
https://ci.syzbot.org/series/51381d54-6fc9-4542-a8cd-eac656a11965

***

WARNING in __dev_queue_xmit

tree:      net-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base:      7a4cd71fa4514cd85df39b3cf99da8142660cdcd
arch:      amd64
compiler:  Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config:    https://ci.syzbot.org/builds/17bc5e9e-8ccc-4afb-a291-312bbc43df20/config
C repro:   https://ci.syzbot.org/findings/20939160-05e8-4589-a6d5-6a253d5e39b0/c_repro
syz repro: https://ci.syzbot.org/findings/20939160-05e8-4589-a6d5-6a253d5e39b0/syz_repro

syzkaller0: entered promiscuous mode
syzkaller0: entered allmulticast mode
------------[ cut here ]------------
reason && reason < __QDISC_DROP_REASON
WARNING: net/sched/sch_generic.c:50 at tcf_kfree_skb_list+0xd6/0x100 net/sched/sch_generic.c:50, CPU#0: syz.0.17/5949
Modules linked in:
CPU: 0 UID: 0 PID: 5949 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:tcf_kfree_skb_list+0xd6/0x100 net/sched/sch_generic.c:50
Code: 89 e8 e8 5d 00 00 00 31 ff 4c 89 e6 ba 40 00 00 00 e8 be e6 d6 ff 4c 8b 24 24 4d 85 e4 74 27 e9 6e ff ff ff e8 1b f3 50 f8 90 <0f> 0b 90 eb c4 44 89 e9 80 e1 07 80 c1 03 38 c1 7c 96 4c 89 ef e8
RSP: 0018:ffffc90003e67360 EFLAGS: 00010293
RAX: ffffffff89718645 RBX: ffff8881133cc000 RCX: ffff8881738b9d40
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 000000000002ffff
RBP: 0000000000000001 R08: ffff88811571195b R09: 1ffff11022ae232b
R10: dffffc0000000000 R11: ffffed1022ae232c R12: ffff88810a9bca80
R13: 0000000000000002 R14: ffff888109569400 R15: ffff888115711800
FS:  000055558d217500(0000) GS:ffff88818e31a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001410 CR3: 0000000166b9c000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 __dev_xmit_skb net/core/dev.c:4272 [inline]
 __dev_queue_xmit+0x18e5/0x3180 net/core/dev.c:4797
 packet_snd net/packet/af_packet.c:3077 [inline]
 packet_sendmsg+0x3eb6/0x50f0 net/packet/af_packet.c:3109
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 ____sys_sendmsg+0x4d7/0x810 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+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6544b9acb9
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:00007ffc871586c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f6544e15fa0 RCX: 00007f6544b9acb9
RDX: 0000000000000004 RSI: 00002000000000c0 RDI: 0000000000000008
RBP: 00007f6544c08bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6544e15fac R14: 00007f6544e15fa0 R15: 00007f6544e15fa0
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@...kaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@...glegroups.com.