------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 24352 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28 Modules linked in: CPU: 1 PID: 24352 Comm: syz-executor.0 Not tainted 5.12.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28 Code: e9 db fe ff ff 48 89 df e8 bc de ee fd e9 8a fe ff ff e8 a2 23 ab fd 48 c7 c7 80 db c1 89 c6 05 5e 25 e8 09 01 e8 98 7a f9 04 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55 RSP: 0018:ffffc9000347fb10 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88801ff63880 RSI: ffffffff815c4d25 RDI: fffff5200068ff54 RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815bdabe R11: 0000000000000000 R12: 0000000000000000 R13: ffff888019ce0018 R14: ffffffff8daa2e40 R15: ffff88802ff97780 FS: 0000000002d58400(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055c232ddd000 CR3: 0000000072170000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_sub_and_test include/linux/refcount.h:283 [inline] __refcount_dec_and_test include/linux/refcount.h:315 [inline] refcount_dec_and_test include/linux/refcount.h:333 [inline] kref_put include/linux/kref.h:64 [inline] nfc_llcp_local_put net/nfc/llcp_core.c:183 [inline] nfc_llcp_local_put+0x1ab/0x200 net/nfc/llcp_core.c:178 llcp_sock_destruct+0x81/0x150 net/nfc/llcp_sock.c:950 __sk_destruct+0x4b/0x900 net/core/sock.c:1795 sk_destruct+0xbd/0xe0 net/core/sock.c:1839 __sk_free+0xef/0x3d0 net/core/sock.c:1850 sock_wfree+0x129/0x240 net/core/sock.c:2074 skb_release_head_state+0x9f/0x250 net/core/skbuff.c:712 skb_release_all net/core/skbuff.c:723 [inline] __kfree_skb net/core/skbuff.c:739 [inline] kfree_skb net/core/skbuff.c:757 [inline] kfree_skb+0xfa/0x3f0 net/core/skbuff.c:751 skb_queue_purge+0x14/0x30 net/core/skbuff.c:3133 nfc_llcp_socket_release+0x2e/0x870 net/nfc/llcp_core.c:73 local_cleanup+0x18/0xb0 net/nfc/llcp_core.c:155 local_release net/nfc/llcp_core.c:174 [inline] kref_put include/linux/kref.h:65 [inline] nfc_llcp_local_put net/nfc/llcp_core.c:183 [inline] nfc_llcp_local_put+0x18c/0x200 net/nfc/llcp_core.c:178 llcp_sock_destruct+0x81/0x150 net/nfc/llcp_sock.c:950 __sk_destruct+0x4b/0x900 net/core/sock.c:1795 sk_destruct+0xbd/0xe0 net/core/sock.c:1839 __sk_free+0xef/0x3d0 net/core/sock.c:1850 sk_free+0x78/0xa0 net/core/sock.c:1861 sock_put include/net/sock.h:1807 [inline] llcp_sock_release+0x3c9/0x580 net/nfc/llcp_sock.c:644 __sock_release+0xcd/0x280 net/socket.c:599 sock_close+0x18/0x20 net/socket.c:1258 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:140 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:208 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x41940b Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44 RSP: 002b:00007ffda8d6b160 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000005 RCX: 000000000041940b RDX: ffffffffffffffbc RSI: 0000000000000081 RDI: 0000000000000004 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000570700 R13: 00007ffda8d6b280 R14: 000000000056bf60 R15: 0000000000081b1d