------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 0 PID: 32719 at lib/refcount.c:25 refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 32719 Comm: syz-executor.1 Not tainted 5.12.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25 Code: 09 31 ff 89 de e8 c7 5e a5 fd 84 db 0f 85 36 ff ff ff e8 0a 58 a5 fd 48 c7 c7 c0 a6 c2 89 c6 05 fa 8d e5 09 01 e8 4a 81 05 05 <0f> 0b e9 17 ff ff ff e8 eb 57 a5 fd 0f b6 1d df 8d e5 09 31 ff 89 RSP: 0018:ffffc9001763fd20 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000040000 RSI: ffffffff815ccd65 RDI: fffff52002ec7f96 RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815c6bce R11: 0000000000000000 R12: ffff88806e874000 R13: ffffc9001763fe34 R14: ffffc9001763fe40 R15: 0000000000000001 FS: 00007f958ecc8700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004e4da5 CR3: 0000000029c7a000 CR4: 00000000001506e0 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+0x68b/0x920 net/can/j1939/main.c:250 j1939_sk_bind+0x426/0xeb0 net/can/j1939/socket.c:479 __sys_bind+0x1e9/0x250 net/socket.c:1637 __do_sys_bind net/socket.c:1648 [inline] __se_sys_bind net/socket.c:1646 [inline] __x64_sys_bind+0x6f/0xb0 net/socket.c:1646 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 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:00007f958ecc8188 EFLAGS: 00000246 ORIG_RAX: 0000000000000031 RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665d9 RDX: 0000000000000018 RSI: 0000000020000240 RDI: 0000000000000008 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c038 R13: 00007ffd084faebf R14: 00007f958ecc8300 R15: 0000000000022000