------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 6980 at lib/refcount.c:28 refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 Modules linked in: CPU: 1 UID: 0 PID: 6980 Comm: syz.1.164 Not tainted 6.12.0-syzkaller-g7b1d1d4cfac0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 lr : refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 sp : ffff8000a1657540 x29: ffff8000a1657540 x28: 0000000000000001 x27: 00000000ffffffff x26: 1fffe0001ab5fc18 x25: dfff800000000000 x24: 0000000000000000 x23: ffff0000c64db4a4 x22: ffff80008a63b670 x21: 0000000000000003 x20: ffff0000c64db4a4 x19: ffff800092b74000 x18: 1fffe000366c8076 x17: ffff80008f8cd000 x16: ffff800080355c58 x15: 0000000000000001 x14: 1fffe000366cab20 x13: ffff8000a1658000 x12: 0000000000000003 x11: 0000000000000001 x10: 0000000000000003 x9 : 7ea2aa182c4fa400 x8 : 7ea2aa182c4fa400 x7 : ffff8000802c419c x6 : 0000000000000000 x5 : 0000000000000001 x4 : 0000000000000001 x3 : 0000000000000000 x2 : 0000000000000006 x1 : ffff80008b6c4000 x0 : ffff800123e21000 Call trace: refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 (P) refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 (L) __refcount_sub_and_test include/linux/refcount.h:275 [inline] __refcount_dec_and_test include/linux/refcount.h:307 [inline] refcount_dec_and_test include/linux/refcount.h:325 [inline] skb_unref include/linux/skbuff.h:1232 [inline] __sk_skb_reason_drop net/core/skbuff.c:1213 [inline] sk_skb_reason_drop+0x210/0x43c net/core/skbuff.c:1241 kfree_skb_reason include/linux/skbuff.h:1262 [inline] kfree_skb include/linux/skbuff.h:1271 [inline] j1939_session_destroy net/can/j1939/transport.c:282 [inline] __j1939_session_release net/can/j1939/transport.c:294 [inline] kref_put include/linux/kref.h:65 [inline] j1939_session_put+0x1c8/0x460 net/can/j1939/transport.c:299 j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline] j1939_sk_sendmsg+0xe88/0x10d0 net/can/j1939/socket.c:1277 sock_sendmsg_nosec net/socket.c:729 [inline] __sock_sendmsg net/socket.c:744 [inline] sock_write_iter+0x2d8/0x448 net/socket.c:1165 do_iter_readv_writev+0x490/0x6d4 vfs_writev+0x410/0xbc8 fs/read_write.c:1064 do_writev+0x178/0x304 fs/read_write.c:1111 __do_sys_writev fs/read_write.c:1184 [inline] __se_sys_writev fs/read_write.c:1181 [inline] __arm64_sys_writev+0x80/0x94 fs/read_write.c:1181 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 irq event stamp: 390 hardirqs last enabled at (389): [] raw_spin_rq_unlock_irq kernel/sched/sched.h:1518 [inline] hardirqs last enabled at (389): [] finish_lock_switch+0xbc/0x1e4 kernel/sched/core.c:5082 hardirqs last disabled at (390): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:488 softirqs last enabled at (360): [] softirq_handle_end kernel/softirq.c:400 [inline] softirqs last enabled at (360): [] handle_softirqs+0xa38/0xbf8 kernel/softirq.c:582 softirqs last disabled at (329): [] __do_softirq+0x14/0x20 kernel/softirq.c:588 ---[ end trace 0000000000000000 ]---