[syzbot] [sctp?] WARNING: refcount bug in sctp_transport_put (6)

Hello,

syzbot found the following issue on:

HEAD commit:    3d6d817622b0 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b9f479580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=80dfcb1a2235b3efc877
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/025cec82d3d2/disk-3d6d8176.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9200091a0c2f/vmlinux-3d6d8176.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b47828829039/bzImage-3d6d8176.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xf4/0x130 lib/refcount.c:28, CPU#1: swapper/1/0
Modules linked in:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:refcount_warn_saturate+0xf4/0x130 lib/refcount.c:28
Code: cc e8 10 93 ec fc 48 8d 3d 09 be 0e 0c 67 48 0f b9 3a e8 ff 92 ec fc 5b 5d e9 d8 23 a0 06 e8 f3 92 ec fc 48 8d 3d fc bd 0e 0c <67> 48 0f b9 3a e8 e2 92 ec fc 5b 5d c3 cc cc cc cc e8 d6 92 ec fc
RSP: 0018:ffffc90000a08c28 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88802afce820 RCX: ffffffff851ddffb
RDX: ffff88801eaca540 RSI: ffffffff851de08d RDI: ffffffff912c9e90
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000003 R11: 0000000000000000 R12: ffff88802afce820
R13: 1ffff9200014118e R14: ffffffff8af14810 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888123eec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe49ed8e10 CR3: 000000005416b000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 sctp_transport_put+0x134/0x180 net/sctp/transport.c:476
 call_timer_fn+0x19a/0x610 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers+0x757/0xb00 kernel/time/timer.c:2374
 __run_timer_base kernel/time/timer.c:2386 [inline]
 __run_timer_base kernel/time/timer.c:2378 [inline]
 run_timer_base+0x114/0x190 kernel/time/timer.c:2395
 run_timer_softirq+0x1a/0x50 kernel/time/timer.c:2405
 handle_softirqs+0x1ea/0x9b0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 55 8c 02 e9 83 4b 03 00 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 83 cf 10 00 fb f4 <c3> cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffc90000197e00 EFLAGS: 00000246
RAX: 0000000002ec63ed RBX: ffff88801eaca540 RCX: ffffffff8bbad335
RDX: 0000000000000000 RSI: ffffffff8e1a9419 RDI: ffffffff8c400480
RBP: ffffed1003d594a8 R08: 0000000000000001 R09: ffffed10170a678d
R10: ffff8880b8533c6b R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 1ffff92000032fc4 R15: dffffc0000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:62 [inline]
 default_idle+0x9/0x10 arch/x86/kernel/process.c:768
 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:199 [inline]
 do_idle+0x3a7/0x5b0 kernel/sched/idle.c:355
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:454
 start_secondary+0x21d/0x2d0 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x158
 </TASK>
----------------
Code disassembly (best guess):
   0:	cc                   	int3
   1:	e8 10 93 ec fc       	call   0xfcec9316
   6:	48 8d 3d 09 be 0e 0c 	lea    0xc0ebe09(%rip),%rdi        # 0xc0ebe16
   d:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  12:	e8 ff 92 ec fc       	call   0xfcec9316
  17:	5b                   	pop    %rbx
  18:	5d                   	pop    %rbp
  19:	e9 d8 23 a0 06       	jmp    0x6a023f6
  1e:	e8 f3 92 ec fc       	call   0xfcec9316
  23:	48 8d 3d fc bd 0e 0c 	lea    0xc0ebdfc(%rip),%rdi        # 0xc0ebe26
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e8 e2 92 ec fc       	call   0xfcec9316
  34:	5b                   	pop    %rbx
  35:	5d                   	pop    %rbp
  36:	c3                   	ret
  37:	cc                   	int3
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	e8 d6 92 ec fc       	call   0xfcec9316


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup