------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28, CPU#0: syz.4.2149/13495
Modules linked in:
CPU: 0 UID: 0 PID: 13495 Comm: syz.4.2149 Tainted: G             L      syzkaller #0 PREEMPT 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
lr : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
sp : ffff80008e987b40
x29: ffff80008e987b40 x28: dfff800000000000 x27: ffff700011d30f84
x26: ffff80008897beb8 x25: dfff800000000000 x24: ffff0000d49d8940
x23: 0000000000000001 x22: ffff0000ddfa0000 x21: 0000000000000000
x20: ffff0000de61d020 x19: ffff800089fbd000 x18: 00000000ffffffff
x17: ffff80008a186c80 x16: ffff80008a5f3e58 x15: ffff0000d2bd8b50
x14: ffff0000d2bd8b30 x13: 0000000000000001 x12: 0000000000000000
x11: 0000000000002197 x10: 0000000000ff0100 x9 : acd1c77677ad5300
x8 : acd1c77677ad5300 x7 : ffff80008047caa0 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff8000802f1374
x2 : 0000000100000101 x1 : ffff0000d2bd8000 x0 : 0000000000000000
Call trace:
 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 (P)
 __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+0x130/0x170 net/sctp/transport.c:476
 sctp_generate_t3_rtx_event+0x230/0x320 net/sctp/sm_sideeffect.c:264
 call_timer_fn+0x194/0xa3c kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers kernel/time/timer.c:2374 [inline]
 __run_timer_base+0x52c/0x74c kernel/time/timer.c:2386
 run_timer_base+0x84/0x1b8 kernel/time/timer.c:2395
 run_timer_softirq+0x20/0x48 kernel/time/timer.c:2405
 handle_softirqs+0x2e4/0xd34 kernel/softirq.c:622
 __do_softirq+0x14/0x20 kernel/softirq.c:656
 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
 call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:889
 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
 invoke_softirq kernel/softirq.c:503 [inline]
 __irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
 irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
 __el1_irq arch/arm64/kernel/entry-common.c:514 [inline]
 el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:526
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:531
 el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:590
 __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline] (P)
 _raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198 (P)
 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline]
 __skb_try_recv_datagram+0x12c/0x3fc net/core/datagram.c:267
 __unix_dgram_recvmsg+0x238/0x898 net/unix/af_unix.c:2587
 unix_dgram_recvmsg+0xcc/0xe4 net/unix/af_unix.c:2686
 sock_recvmsg_nosec+0x90/0xe8 net/socket.c:1137
 ____sys_recvmsg+0x4f8/0x604 net/socket.c:2916
 ___sys_recvmsg+0x16c/0x1f4 net/socket.c:2960
 do_recvmmsg+0x2a8/0x7e8 net/socket.c:3055
 __sys_recvmmsg+0x1e0/0x270 net/socket.c:3129
 __do_sys_recvmmsg net/socket.c:3152 [inline]
 __se_sys_recvmmsg net/socket.c:3145 [inline]
 __arm64_sys_recvmmsg+0xd0/0xf8 net/socket.c:3145
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:740
 el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:759
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594
irq event stamp: 414375
hardirqs last  enabled at (414374): [<ffff8000867a27cc>] irqentry_exit_to_kernel_mode_after_preempt include/linux/irq-entry-common.h:507 [inline]
hardirqs last  enabled at (414374): [<ffff8000867a27cc>] arm64_exit_to_kernel_mode+0x80/0x94 arch/arm64/kernel/entry-common.c:62
hardirqs last disabled at (414375): [<ffff80008679e6f8>] el1_brk64+0x20/0x54 arch/arm64/kernel/entry-common.c:429
softirqs last  enabled at (414212): [<ffff800080309080>] softirq_handle_end kernel/softirq.c:468 [inline]
softirqs last  enabled at (414212): [<ffff800080309080>] handle_softirqs+0xbc4/0xd34 kernel/softirq.c:650
softirqs last disabled at (414233): [<ffff8000800204b0>] __do_softirq+0x14/0x20 kernel/softirq.c:656
---[ end trace 0000000000000000 ]---