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Date: Mon, 10 Jun 2024 19:15:03 -0700
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Subject: Re: [syzbot] [bluetooth?] general protection fault in l2cap_sock_recv_cb
From: syzbot <syzbot+b7f6f8c9303466e16c8a@syzkaller.appspotmail.com>
To: eadavis@qq.com, linux-kernel@vger.kernel.org, 
	syzkaller-bugs@googlegroups.com
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Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: refcount bug in l2cap_sock_recv_cb

------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 4478 at lib/refcount.c:25 refcount_warn_saturate+0x13a/0x1d0 lib/refcount.c:25
Modules linked in:
CPU: 1 PID: 4478 Comm: kworker/u9:1 Not tainted 6.10.0-rc1-syzkaller-00267-gcc8ed4d0a848-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Workqueue: hci0 hci_rx_work
RIP: 0010:refcount_warn_saturate+0x13a/0x1d0 lib/refcount.c:25
Code: c0 cb 1e 8c e8 c7 ae b1 fc 90 0f 0b 90 90 eb b9 e8 1b 80 ef fc c6 05 9a 04 f0 0a 01 90 48 c7 c7 20 cc 1e 8c e8 a7 ae b1 fc 90 <0f> 0b 90 90 eb 99 e8 fb 7f ef fc c6 05 7b 04 f0 0a 01 90 48 c7 c7
RSP: 0018:ffffc9000d40f440 EFLAGS: 00010246
RAX: 8178418b52383400 RBX: ffff88807498d080 RCX: ffff88802fa51e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffffffff815846c2 R09: 1ffff110172a519a
R10: dffffc0000000000 R11: ffffed10172a519b R12: ffff88807498e4a0
R13: ffff88807498e000 R14: dffffc0000000000 R15: 1ffff1100e931c94
FS:  0000000000000000(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbe77aafffc CR3: 000000000e132000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_inc include/linux/refcount.h:241 [inline]
 refcount_inc include/linux/refcount.h:258 [inline]
 sock_hold include/net/sock.h:774 [inline]
 l2cap_sock_recv_cb+0x53d/0x600 net/bluetooth/l2cap_sock.c:1509
 l2cap_conless_channel net/bluetooth/l2cap_core.c:6780 [inline]
 l2cap_recv_frame+0x8b6d/0x10670 net/bluetooth/l2cap_core.c:6833
 hci_acldata_packet net/bluetooth/hci_core.c:3842 [inline]
 hci_rx_work+0x50f/0xca0 net/bluetooth/hci_core.c:4079
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


Tested on:

commit:         cc8ed4d0 Merge tag 'drm-fixes-2024-06-01' of https://g..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=149a3bf6980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=47d282ddffae809f
dashboard link: https://syzkaller.appspot.com/bug?extid=b7f6f8c9303466e16c8a
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=106af454980000