------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#0: ktimers/0/16
Modules linked in:
CPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25
Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 fb c3 32 fd 48 8d 3d 04 7b c1 0a 67 48 0f b9 3a eb 4a e8 e8 c3 32 fd 48 8d 3d 01 7b c1 0a <67> 48 0f b9 3a eb 37 e8 d5 c3 32 fd 48 8d 3d fe 7a c1 0a 67 48 0f
RSP: 0018:ffffc90000157968 EFLAGS: 00010246
RAX: ffffffff84907088 RBX: 0000000000000002 RCX: ffff88801c6ddac0
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffffffff8f51eb90
RBP: 0000000000000000 R08: ffff88801c6ddac0 R09: 0000000000000005
R10: 0000000000000100 R11: 0000000000000004 R12: dffffc0000000000
R13: 0000000000000001 R14: ffff888036cda004 R15: ffff888036cda640
FS: 0000000000000000(0000) GS:ffff8881265c9000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000404030 CR3: 000000000d9b4000 CR4: 00000000003526f0
Call Trace:
<TASK>
sctp_generate_timeout_event+0x1c8/0x390 net/sctp/sm_sideeffect.c:284
call_timer_fn+0x192/0x5a0 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers kernel/time/timer.c:2373 [inline]
__run_timer_base+0x6a3/0x9f0 kernel/time/timer.c:2385
run_timer_base kernel/time/timer.c:2394 [inline]
run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2404
handle_softirqs+0x1de/0x640 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
run_ktimerd+0x69/0x100 kernel/softirq.c:1138
smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
kthread+0x726/0x8b0 kernel/kthread.c:463
ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
----------------
Code disassembly (best guess):
0: eb 66 jmp 0x68
2: 85 db test %ebx,%ebx
4: 74 3e je 0x44
6: 83 fb 01 cmp $0x1,%ebx
9: 75 4c jne 0x57
b: e8 fb c3 32 fd call 0xfd32c40b
10: 48 8d 3d 04 7b c1 0a lea 0xac17b04(%rip),%rdi # 0xac17b1b
17: 67 48 0f b9 3a ud1 (%edx),%rdi
1c: eb 4a jmp 0x68
1e: e8 e8 c3 32 fd call 0xfd32c40b
23: 48 8d 3d 01 7b c1 0a lea 0xac17b01(%rip),%rdi # 0xac17b2b
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: eb 37 jmp 0x68
31: e8 d5 c3 32 fd call 0xfd32c40b
36: 48 8d 3d fe 7a c1 0a lea 0xac17afe(%rip),%rdi # 0xac17b3b
3d: 67 addr32
3e: 48 rex.W
3f: 0f .byte 0xf