From: syzbot <syzbot+80dfcb1a2235b3efc877@syzkaller.appspotmail.com>
To: davem@davemloft.net, edumazet@google.com, horms@kernel.org,
kuba@kernel.org, linux-kernel@vger.kernel.org,
linux-sctp@vger.kernel.org, lucien.xin@gmail.com,
marcelo.leitner@gmail.com, netdev@vger.kernel.org,
pabeni@redhat.com, syzkaller-bugs@googlegroups.com
Subject: [syzbot] [sctp?] WARNING: refcount bug in sctp_transport_put (6)
Date: Thu, 13 Aug 2026 01:59:31 -0700 [thread overview]
Message-ID: <6a7d8773.c5ad36c8.12f49d.002e.GAE@google.com> (raw)
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: syzbot+80dfcb1a2235b3efc877@syzkaller.appspotmail.com
------------[ 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
---
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reply other threads:[~2026-08-13 8:59 UTC|newest]
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