[Android 5.10] BUG: soft lockup in tc_modify_qdisc (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dce613ec61e0 Revert "net: vlan: fix VLAN 0 refcount imbala..
git tree: android13-5.10-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=146f087c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a0215b31c33ff34
dashboard link: https://syzkaller.appspot.com/bug?extid=2261107a6ec25094b776
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15587162580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=144f4962580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8222eacbe410/disk-dce613ec.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/35b1d08ca0b5/vmlinux-dce613ec.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4cd30bfc3355/bzImage-dce613ec.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+226110...@syzkaller.appspotmail.com

RBP: 00007f9fb3e90e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9fb4044fa0 R14: 00007f9fb4044fa0 R15: 0000000000000003
watchdog: BUG: soft lockup - CPU#1 stuck for 123s! [syz.2.17:381]
Modules linked in:
CPU: 1 PID: 381 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
RIP: 0010:qdisc_dev include/net/sch_generic.h:603 [inline]
RIP: 0010:qdisc_match_from_root net/sched/sch_api.c:263 [inline]
RIP: 0010:qdisc_lookup+0x81/0x4e0 net/sched/sch_api.c:304
Code: 4d 8d 66 40 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 df d0 f2 fd 4d 8b 24 24 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 <74> 08 4c 89 e7 e8 c5 d0 f2 fd 4d 8b 3c 24 4d 85 ff 74 7b 4d 8d 66
RSP: 0018:ffffc9000435eee8 EFLAGS: 00000246
RAX: 1ffff11021d7d400 RBX: 00000000ffff0000 RCX: 0000000000000000
RDX: ffff888128d262c0 RSI: 00000000ffff0000 RDI: 0000000000000000
RBP: ffffc9000435ef18 R08: ffff888128d262c0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000000 R12: ffff88810ebea000
R13: dffffc0000000000 R14: ffff888128f0f000 R15: ffff88810fdab040
FS: 000055557558c500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001200 CR3: 000000010fce0000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
qdisc_tree_reduce_backlog+0x111/0x340 net/sched/sch_api.c:793
fq_change+0xb9e/0x10a0 net/sched/sch_fq.c:915
fq_init+0x3e3/0x5d0 net/sched/sch_fq.c:963
qdisc_create+0x780/0x1040 net/sched/sch_api.c:1265
tc_modify_qdisc+0x8da/0x14c0 net/sched/sch_api.c:1725
rtnetlink_rcv_msg+0x9db/0xb90 net/core/rtnetlink.c:5610
netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2503
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5628
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x88d/0xb30 net/netlink/af_netlink.c:1914
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2376
___sys_sendmsg+0x1f0/0x260 net/socket.c:2430
__sys_sendmsg net/socket.c:2459 [inline]
__do_sys_sendmsg net/socket.c:2468 [inline]
__se_sys_sendmsg net/socket.c:2466 [inline]
__x64_sys_sendmsg+0x1e2/0x2a0 net/socket.c:2466
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f9fb3e0dbe9
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:00007ffd68ee66d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f9fb4044fa0 RCX: 00007f9fb3e0dbe9
RDX: 0000000000000010 RSI: 0000200000001200 RDI: 0000000000000006
RBP: 00007f9fb3e90e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9fb4044fa0 R14: 00007f9fb4044fa0 R15: 0000000000000003
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0x12/0x20 arch/x86/kernel/process.c:717


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