------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 11810 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28 Modules linked in: CPU: 1 PID: 11810 Comm: syz-executor.1 Not tainted 5.12.0-rc8-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28 Code: e9 db fe ff ff 48 89 df e8 7c dd ee fd e9 8a fe ff ff e8 32 22 ab fd 48 c7 c7 80 db c1 89 c6 05 1e 1e e8 09 01 e8 58 85 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:ffffc9002a9c7ae0 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff888014743880 RSI: ffffffff815c4d25 RDI: fffff52005538f4e RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815bdabe R11: 0000000000000000 R12: 0000000000000000 R13: ffff888019fdf018 R14: ffffffff8daa2cc0 R15: ffff888023d5ceb0 FS: 0000000000000000(0000) GS:ffff88802cb00000(0063) knlGS:000000000ad85380 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 00007f85cf473020 CR3: 0000000070626000 CR4: 0000000000150ee0 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 __do_fast_syscall_32+0x62/0x90 arch/x86/entry/common.c:143 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c RIP: 0023:0xf7f7e549 Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 RSP: 002b:00000000ffc14c10 EFLAGS: 00000286 ORIG_RAX: 0000000000000006 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000000002 RDX: 0000000000000000 RSI: 000000000816c000 RDI: 0000000000000000 RBP: 000000000816c000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000