------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 5312 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28 Modules linked in: CPU: 0 UID: 0 PID: 5312 Comm: syz.0.0 Not tainted 6.13.0-rc1-syzkaller-00002-gcdd30ebb1b9f #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:ffffc9000d347b58 EFLAGS: 00010246 RAX: 16c9c3526c763c00 RBX: ffff888032f99864 RCX: ffff888000e10000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000003 R08: ffffffff81601c02 R09: 1ffff11003f8519a R10: dffffc0000000000 R11: ffffed1003f8519b R12: ffff88804032c068 R13: ffff888032f99864 R14: 1ffff11008065818 R15: ffff88804032c000 FS: 000055555b296500(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f95282d49a0 CR3: 0000000042ec0000 CR4: 0000000000352ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: 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_queue_drop_all+0x191/0x240 net/can/j1939/socket.c:144 j1939_sk_release+0x2ae/0x670 net/can/j1939/socket.c:642 __sock_release net/socket.c:640 [inline] sock_close+0xbc/0x240 net/socket.c:1408 __fput+0x23c/0xa50 fs/file_table.c:450 task_work_run+0x24f/0x310 kernel/task_work.c:239 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop kernel/entry/common.c:114 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x13f/0x340 kernel/entry/common.c:218 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f952757ff19 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:00007fffd81c4578 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 0000000000013cb3 RCX: 00007f952757ff19 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007f9527747ba0 R08: 0000000000000001 R09: 00007fffd81c485f R10: 00007f95273ff02c R11: 0000000000000246 R12: 0000000000013d07 R13: 00007f9527745fa0 R14: 0000000000000032 R15: ffffffffffffffff