EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback. ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 8546 at lib/refcount.c:28 refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 Modules linked in: CPU: 0 UID: 0 PID: 8546 Comm: syz.0.338 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 : ffff80009dbc76e0 x29: ffff80009dbc76e0 x28: 0000000000000001 x27: 00000000ffffffff x26: 1fffe000198ca498 x25: dfff800000000000 x24: 0000000000000000 x23: ffff0000cdc6b4a4 x22: ffff80008a63b670 x21: 0000000000000003 x20: ffff0000cdc6b4a4 x19: ffff800092b74000 x18: 1fffe000366c3876 x17: ffff80008f8cd000 x16: ffff800080355c58 x15: 0000000000000001 x14: 1fffe000366c6320 x13: ffff80009dbc8000 x12: 0000000000000003 x11: 0000000000000001 x10: 0000000000000003 x9 : 671597cc2ab3dd00 x8 : 671597cc2ab3dd00 x7 : ffff8000802c419c x6 : 0000000000000000 x5 : 0000000000000001 x4 : 0000000000000001 x3 : 0000000000000000 x2 : 0000000000000006 x1 : ffff80008b6c4000 x0 : ffff800123dfd000 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] ____sys_sendmsg+0x56c/0x840 net/socket.c:2607 ___sys_sendmsg net/socket.c:2661 [inline] __sys_sendmsg+0x26c/0x33c net/socket.c:2690 __do_sys_sendmsg net/socket.c:2699 [inline] __se_sys_sendmsg net/socket.c:2697 [inline] __arm64_sys_sendmsg+0x80/0x94 net/socket.c:2697 __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: 5026 hardirqs last enabled at (5025): [] raw_spin_rq_unlock_irq kernel/sched/sched.h:1518 [inline] hardirqs last enabled at (5025): [] finish_lock_switch+0xbc/0x1e4 kernel/sched/core.c:5082 hardirqs last disabled at (5026): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:488 softirqs last enabled at (4998): [] softirq_handle_end kernel/softirq.c:400 [inline] softirqs last enabled at (4998): [] handle_softirqs+0xa38/0xbf8 kernel/softirq.c:582 softirqs last disabled at (4915): [] __do_softirq+0x14/0x20 kernel/softirq.c:588 ---[ end trace 0000000000000000 ]---