refcount_t: addition on 0; use-after-free. WARNING: CPU: 0 PID: 9985 at lib/refcount.c:25 refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 9985 Comm: syz-executor.1 Not tainted 5.14.0-rc1-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 RIP: 0010:refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25 Code: 09 31 ff 89 de e8 47 d6 9e fd 84 db 0f 85 36 ff ff ff e8 8a ce 9e fd 48 c7 c7 c0 d1 e2 89 c6 05 40 b1 81 09 01 e8 42 8c 11 05 <0f> 0b e9 17 ff ff ff e8 6b ce 9e fd 0f b6 1d 25 b1 81 09 31 ff 89 RSP: 0018:ffffc90002957d20 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000040000 RSI: ffffffff815c9ca5 RDI: fffff5200052af96 RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815c3aae R11: 0000000000000000 R12: ffff88800ee38000 R13: ffff88800ee38000 R14: ffff8880770e0568 R15: ffff88800ee98050 FS: 00007fd8c568b700(0000) GS:ffff88802cd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000541198 CR3: 000000004dcd8000 CR4: 0000000000150ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_add include/linux/refcount.h:199 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] kref_get include/linux/kref.h:45 [inline] j1939_netdev_start+0x806/0x920 net/can/j1939/main.c:275 j1939_sk_bind+0x426/0xeb0 net/can/j1939/socket.c:482 __sys_bind+0x1e9/0x250 net/socket.c:1679 __do_sys_bind net/socket.c:1690 [inline] __se_sys_bind net/socket.c:1688 [inline] __x64_sys_bind+0x6f/0xb0 net/socket.c:1688 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4665d9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fd8c568b188 EFLAGS: 00000246 ORIG_RAX: 0000000000000031 RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9 RDX: 0000000000000018 RSI: 0000000020000200 RDI: 0000000000000003 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007ffe8323ff3f R14: 00007fd8c568b300 R15: 0000000000022000