------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 5313 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28 Modules linked in: CPU: 0 UID: 0 PID: 5313 Comm: syz.0.0 Not tainted 6.13.0-rc1-syzkaller-00005-gceb8bf2ceaa7 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28 Code: e0 1e 5f 8c e8 07 c1 95 fc 90 0f 0b 90 90 eb 99 e8 ab 19 d5 fc c6 05 ed 27 39 0b 01 90 48 c7 c7 40 1f 5f 8c e8 e7 c0 95 fc 90 <0f> 0b 90 90 e9 76 ff ff ff e8 88 19 d5 fc c6 05 c7 27 39 0b 01 90 RSP: 0018:ffffc9000d50f8e8 EFLAGS: 00010246 RAX: 47a91e9c01b72e00 RBX: ffff8880122e1ae4 RCX: 0000000000100000 RDX: ffffc9000e352000 RSI: 00000000000009ac RDI: 00000000000009ad RBP: 0000000000000003 R08: ffffffff81601c02 R09: 1ffff11003f8519a R10: dffffc0000000000 R11: ffffed1003f8519b R12: ffff888045a8d068 R13: ffff8880122e1ae4 R14: 1ffff11008b51a18 R15: ffff888045a8d000 FS: 00007f789176c6c0(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000040 CR3: 0000000011c50000 CR4: 0000000000352ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> kfree_skb_reason include/linux/skbuff.h:1263 [inline] kfree_skb include/linux/skbuff.h:1272 [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+0x1ed/0x440 net/can/j1939/transport.c:299 j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline] j1939_sk_sendmsg+0x121b/0x14c0 net/can/j1939/socket.c:1277 sock_sendmsg_nosec net/socket.c:711 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:726 ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2583 ___sys_sendmsg net/socket.c:2637 [inline] __sys_sendmsg+0x269/0x350 net/socket.c:2669 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f789097ff19 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f789176c058 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f7890b45fa0 RCX: 00007f789097ff19 RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000004 RBP: 00007f78909f3986 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f7890b45fa0 R15: 00007ffe85f577b8 </TASK>