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SubjectKASAN: use-after-free Read in hci_send_acl
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Hello,

syzbot found the following issue on:

HEAD commit: ac3a0c84 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13482904900000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0cfcf935bcc94d2
dashboard link: https://syzkaller.appspot.com/bug?extid=98228e7407314d2d4ba2
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=152f1904900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1482dfca900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98228e7407314d2d4ba2@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in hci_send_acl+0xabe/0xc60 net/bluetooth/hci_core.c:3991
Read of size 8 at addr ffff8880a6ff8818 by task kworker/u5:2/6855

CPU: 1 PID: 6855 Comm: kworker/u5:2 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: hci0 hci_rx_work
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
hci_send_acl+0xabe/0xc60 net/bluetooth/hci_core.c:3991
l2cap_send_cmd+0x6d5/0x8a0 net/bluetooth/l2cap_core.c:949
l2cap_send_move_chan_cfm_icid net/bluetooth/l2cap_core.c:4917 [inline]
l2cap_move_fail net/bluetooth/l2cap_core.c:5401 [inline]
l2cap_move_channel_rsp net/bluetooth/l2cap_core.c:5440 [inline]
l2cap_bredr_sig_cmd net/bluetooth/l2cap_core.c:5719 [inline]
l2cap_sig_channel net/bluetooth/l2cap_core.c:6418 [inline]
l2cap_recv_frame+0x6936/0xae10 net/bluetooth/l2cap_core.c:7660
l2cap_recv_acldata+0x7f6/0x8e0 net/bluetooth/l2cap_core.c:8313
hci_acldata_packet net/bluetooth/hci_core.c:4520 [inline]
hci_rx_work+0x4c7/0xb10 net/bluetooth/hci_core.c:4710
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Allocated by task 6855:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
hci_chan_create+0x9b/0x330 net/bluetooth/hci_conn.c:1692
l2cap_conn_add.part.0+0x1e/0xe10 net/bluetooth/l2cap_core.c:7699
l2cap_conn_add net/bluetooth/l2cap_core.c:8139 [inline]
l2cap_connect_cfm+0x23b/0x1090 net/bluetooth/l2cap_core.c:8097
hci_connect_cfm include/net/bluetooth/hci_core.h:1340 [inline]
hci_remote_features_evt net/bluetooth/hci_event.c:3210 [inline]
hci_event_packet+0x3e01/0x86f5 net/bluetooth/hci_event.c:6061
hci_rx_work+0x22e/0xb10 net/bluetooth/hci_core.c:4705
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Freed by task 6855:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x103/0x2c0 mm/slab.c:3757
hci_disconn_loglink_complete_evt net/bluetooth/hci_event.c:4999 [inline]
hci_event_packet+0x319a/0x86f5 net/bluetooth/hci_event.c:6188
hci_rx_work+0x22e/0xb10 net/bluetooth/hci_core.c:4705
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff8880a6ff8800
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 24 bytes inside of
128-byte region [ffff8880a6ff8800, ffff8880a6ff8880)
The buggy address belongs to the page:
page:ffffea00029bfe00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880a6ff8c00
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002934388 ffff8880aa001540 ffff8880aa000700
raw: ffff8880a6ff8c00 ffff8880a6ff8000 000000010000000c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a6ff8700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a6ff8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a6ff8800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a6ff8880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a6ff8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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@googlegroups.com.

syzbot will keep track of this issue. See:
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

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