Hello, syzbot found the following issue on: HEAD commit: 75887e88 Merge branch '40GbE' of git://git.kernel.org/pub/.. git tree: net console output: https://syzkaller.appspot.com/x/log.txt?x=131a634ed00000 kernel config: https://syzkaller.appspot.com/x/.config?x=5adab0bdee099d7a dashboard link: https://syzkaller.appspot.com/bug?extid=0aabbccfb4ec7b744ffd syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15bcd6f6d00000 The issue was bisected to: commit 997acaf6b4b59c6a9c259740312a69ea549cc684 Author: Mark Rutland <mark.rutland@xxxxxxx> Date: Mon Jan 11 15:37:07 2021 +0000 lockdep: report broken irq restoration bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12279b4ed00000 final oops: https://syzkaller.appspot.com/x/report.txt?x=11279b4ed00000 console output: https://syzkaller.appspot.com/x/log.txt?x=16279b4ed00000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0aabbccfb4ec7b744ffd@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 997acaf6b4b5 ("lockdep: report broken irq restoration") ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 11133 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28 Modules linked in: CPU: 1 PID: 11133 Comm: syz-executor.0 Not tainted 5.12.0-rc4-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 fc ee ee fd e9 8a fe ff ff e8 42 44 ab fd 48 c7 c7 c0 d8 c1 89 c6 05 eb 44 e9 09 01 e8 7c 9b fc 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:ffffc900033f7b10 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff888040038000 RSI: ffffffff815c4d15 RDI: fffff5200067ef54 RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815bdaae R11: 0000000000000000 R12: 0000000000000000 R13: ffff88814429f018 R14: ffffffff8dab2ec0 R15: ffff888030b20d38 FS: 0000000001fa6400(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000540198 CR3: 00000000142c1000 CR4: 00000000001506e0 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 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches
