[syzbot] [net?] WARNING in rcuref_put_slowpath

[syzbot <syzbot+e14bc5d4942756023b77@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    4fa3f5fabb30 Add linux-next specific files for 20260616
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1427abd2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6c414e1864e61ef6
dashboard link: https://syzkaller.appspot.com/bug?extid=e14bc5d4942756023b77
compiler:       Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf5b803a695d/disk-4fa3f5fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/47871e7c589e/vmlinux-4fa3f5fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/53cd9ef32a2b/bzImage-4fa3f5fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e14bc5d4942756023b77@syzkaller.appspotmail.com

------------[ cut here ]------------
rcuref - imbalanced put()
WARNING: lib/rcuref.c:266 at rcuref_put_slowpath+0x16e/0x1d0 lib/rcuref.c:266, CPU#0: ktimers/0/16
Modules linked in:
CPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:rcuref_put_slowpath+0x16e/0x1d0 lib/rcuref.c:266
Code: c1 e8 03 42 0f b6 04 38 84 c0 75 48 c7 03 00 00 00 a0 31 c0 e9 6d ff ff ff e8 fe 13 80 06 e8 49 d7 14 fd 48 8d 3d 62 f3 e6 0a <67> 48 0f b9 3a 48 89 df be 04 00 00 00 e8 40 b3 80 fd 48 89 d8 48
RSP: 0018:ffffc90000157560 EFLAGS: 00010246
RAX: ffffffff84b04017 RBX: ffff888025328740 RCX: ffff88801d680000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffffffff8f973380
RBP: ffffc900001575e8 R08: 0000000000000000 R09: 0000000000000100
R10: dffffc0000000000 R11: ffffed1004a650e9 R12: 1ffff9200002aeac
R13: dffffc0000000000 R14: 00000000dfffffff R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888125ed3000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f67d5f2c558 CR3: 0000000026bb4000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __rcuref_put include/linux/rcuref.h:117 [inline]
 rcuref_put+0x15b/0x170 include/linux/rcuref.h:173
 dst_release+0x31/0x1b0 net/core/dst.c:251
 dst_cache_per_cpu_get+0x25a/0x2d0 net/core/dst_cache.c:57
 dst_cache_get+0x10d/0x1e0 net/core/dst_cache.c:75
 tipc_udp_xmit+0xcf/0xb30 net/tipc/udp_media.c:177
 tipc_bearer_xmit_skb+0x2b3/0x400 net/tipc/bearer.c:576
 tipc_disc_timeout+0x642/0x790 net/tipc/discover.c:338
 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers kernel/time/timer.c:2374 [inline]
 __run_timer_base+0x67b/0x9b0 kernel/time/timer.c:2386
 run_timer_base kernel/time/timer.c:2395 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405
 handle_softirqs+0x1d9/0x6c0 kernel/softirq.c:626
 __do_softirq kernel/softirq.c:660 [inline]
 run_ktimerd+0x69/0x100 kernel/softirq.c:1155
 smpboot_thread_fn+0x57c/0xa80 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess):
   0:	c1 e8 03             	shr    $0x3,%eax
   3:	42 0f b6 04 38       	movzbl (%rax,%r15,1),%eax
   8:	84 c0                	test   %al,%al
   a:	75 48                	jne    0x54
   c:	c7 03 00 00 00 a0    	movl   $0xa0000000,(%rbx)
  12:	31 c0                	xor    %eax,%eax
  14:	e9 6d ff ff ff       	jmp    0xffffff86
  19:	e8 fe 13 80 06       	call   0x680141c
  1e:	e8 49 d7 14 fd       	call   0xfd14d76c
  23:	48 8d 3d 62 f3 e6 0a 	lea    0xae6f362(%rip),%rdi        # 0xae6f38c
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	48 89 df             	mov    %rbx,%rdi
  32:	be 04 00 00 00       	mov    $0x4,%esi
  37:	e8 40 b3 80 fd       	call   0xfd80b37c
  3c:	48 89 d8             	mov    %rbx,%rax
  3f:	48                   	rex.W


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