syzbot

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refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 20874 at lib/refcount.c:25 refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25
Modules linked in:
CPU: 1 PID: 20874 Comm: syz-executor.0 Not tainted 5.14.0-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 77 37 9f fd 84 db 0f 85 36 ff ff ff e8 2a 31 9f fd 48 c7 c7 a0 76 e3 89 c6 05 a8 9e 81 09 01 e8 95 b8 11 05 <0f> 0b e9 17 ff ff ff e8 0b 31 9f fd 0f b6 1d 8d 9e 81 09 31 ff 89
RSP: 0018:ffffc9000a697d20 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88802e710000 RSI: ffffffff815d8625 RDI: fffff520014d2f96
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815d245e R11: 0000000000000000 R12: ffff88803d1f8000
R13: ffffc9000a697e34 R14: ffffc9000a697e40 R15: 0000000000000001
FS:  00007f67dc2a5700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe3cf7e3000 CR3: 0000000012bfe000 CR4: 00000000001506f0
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:254
 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: 0033:0x4665f9
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:00007f67dc2a5188 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665f9
RDX: 0000000000000018 RSI: 0000000020000240 RDI: 0000000000000004
RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffdf3844b0f R14: 00007f67dc2a5300 R15: 0000000000022000