BUG: corrupted list in bt_accept

BUG: corrupted list in bt_accept_unlink
Status: upstream: reported syz repro on 2020/08/14 23:30
Reported-by: syzbot+7f4d3ecf4d3480301722@syzkaller.appspotmail.com
First crash: 399d, last: 399d

Cause bisection: failed (bisect log)

Fix bisection: failed (bisect log)

similar bugs (1):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	BUG: corrupted list in bt_accept_unlink	syz		unreliable	1	285d	405d	0/1	upstream: reported syz repro on 2020/08/09 08:38

Sample crash report:

list_del corruption. prev->next should be ffff8880913ab4b8, but was ffff8880890c54b8
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:51!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 17 Comm: kworker/1:0 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events l2cap_chan_timeout
RIP: 0010:__list_del_entry_valid.cold+0xf/0x55 lib/list_debug.c:51
Code: e8 5a ab bf fd 0f 0b 48 89 f1 48 c7 c7 40 ff 93 88 4c 89 e6 e8 46 ab bf fd 0f 0b 48 89 ee 48 c7 c7 e0 00 94 88 e8 35 ab bf fd <0f> 0b 4c 89 ea 48 89 ee 48 c7 c7 20 00 94 88 e8 21 ab bf fd 0f 0b
RSP: 0018:ffffc90000d8fb18 EFLAGS: 00010282
RAX: 0000000000000054 RBX: ffff8880913ab4b8 RCX: 0000000000000000
RDX: ffff8880a968a480 RSI: ffffffff815dbc57 RDI: fffff520001b1f55
RBP: ffff8880913ab4b8 R08: 0000000000000054 R09: ffff8880ae7318e7
R10: 0000000000000000 R11: 00000000000c3a18 R12: ffff8880890c54b8
R13: ffff88809914f4b8 R14: ffff88809914f000 R15: 0000000000000008
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000081570f0 CR3: 00000000a6dc2000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __list_del_entry include/linux/list.h:132 [inline]
 list_del_init include/linux/list.h:204 [inline]
 bt_accept_unlink+0x26/0x280 net/bluetooth/af_bluetooth.c:187
 l2cap_sock_teardown_cb+0x197/0x400 net/bluetooth/l2cap_sock.c:1544
 l2cap_chan_del+0xad/0x1300 net/bluetooth/l2cap_core.c:618
 l2cap_chan_close+0x118/0xb10 net/bluetooth/l2cap_core.c:823
 l2cap_chan_timeout+0x173/0x450 net/bluetooth/l2cap_core.c:436
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Modules linked in:
---[ end trace ea2f8b77c156d63d ]---
RIP: 0010:__list_del_entry_valid.cold+0xf/0x55 lib/list_debug.c:51
Code: e8 5a ab bf fd 0f 0b 48 89 f1 48 c7 c7 40 ff 93 88 4c 89 e6 e8 46 ab bf fd 0f 0b 48 89 ee 48 c7 c7 e0 00 94 88 e8 35 ab bf fd <0f> 0b 4c 89 ea 48 89 ee 48 c7 c7 20 00 94 88 e8 21 ab bf fd 0f 0b
RSP: 0018:ffffc90000d8fb18 EFLAGS: 00010282
RAX: 0000000000000054 RBX: ffff8880913ab4b8 RCX: 0000000000000000
RDX: ffff8880a968a480 RSI: ffffffff815dbc57 RDI: fffff520001b1f55
RBP: ffff8880913ab4b8 R08: 0000000000000054 R09: ffff8880ae7318e7
R10: 0000000000000000 R11: 00000000000c3a18 R12: ffff8880890c54b8
R13: ffff88809914f4b8 R14: ffff88809914f000 R15: 0000000000000008
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000080f0b38 CR3: 0000000009a8d000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce-386	2020/08/14 19:26	upstream	a1d21081a60d	424dd8e7	.config	log	report	syz