[syzbot] KASAN: use-after-free Read in l2cap_conn_del

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syzbot

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Sep 26, 2022, 12:43:43 PMSep 26
to da...@davemloft.net, edum...@google.com, johan....@gmail.com, ku...@kernel.org, linux-b...@vger.kernel.org, linux-...@vger.kernel.org, luiz....@gmail.com, mar...@holtmann.org, net...@vger.kernel.org, pab...@redhat.com, syzkall...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: aaa11ce2ffc8 Add linux-next specific files for 20220923
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14b32754880000
kernel config: https://syzkaller.appspot.com/x/.config?x=186d1ff305f10294
dashboard link: https://syzkaller.appspot.com/bug?extid=03450dacbc626061c3a3
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12d389c4880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14269e38880000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+03450d...@syzkaller.appspotmail.com

Bluetooth: hci0: hardware error 0xff
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: use-after-free in atomic_long_read include/linux/atomic/atomic-instrumented.h:1265 [inline]
BUG: KASAN: use-after-free in __mutex_unlock_slowpath+0xa6/0x5e0 kernel/locking/mutex.c:916
Read of size 8 at addr ffff888020ab34b8 by task kworker/u5:0/49

CPU: 0 PID: 49 Comm: kworker/u5:0 Not tainted 6.0.0-rc6-next-20220923-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
Workqueue: hci0 hci_error_reset
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:284 [inline]
print_report+0x15e/0x45d mm/kasan/report.c:395
kasan_report+0xbb/0x1f0 mm/kasan/report.c:495
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:72 [inline]
atomic_long_read include/linux/atomic/atomic-instrumented.h:1265 [inline]
__mutex_unlock_slowpath+0xa6/0x5e0 kernel/locking/mutex.c:916
l2cap_chan_unlock include/net/bluetooth/l2cap.h:860 [inline]
l2cap_conn_del+0x404/0x7b0 net/bluetooth/l2cap_core.c:1932
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:8214 [inline]
l2cap_disconn_cfm+0x8c/0xc0 net/bluetooth/l2cap_core.c:8207
hci_disconn_cfm include/net/bluetooth/hci_core.h:1787 [inline]
hci_conn_hash_flush+0x122/0x260 net/bluetooth/hci_conn.c:2430
hci_dev_close_sync+0x5c4/0x1200 net/bluetooth/hci_sync.c:4804
hci_dev_do_close+0x2d/0x70 net/bluetooth/hci_core.c:554
hci_error_reset+0x9e/0x140 net/bluetooth/hci_core.c:1059
process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>

Allocated by task 3621:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
kasan_set_track+0x21/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:371 [inline]
____kasan_kmalloc mm/kasan/common.c:330 [inline]
__kasan_kmalloc+0xa1/0xb0 mm/kasan/common.c:380
kmalloc include/linux/slab.h:559 [inline]
kzalloc include/linux/slab.h:695 [inline]
l2cap_chan_create+0x40/0x930 net/bluetooth/l2cap_core.c:466
a2mp_chan_open net/bluetooth/a2mp.c:771 [inline]
amp_mgr_create+0x8f/0x960 net/bluetooth/a2mp.c:862
a2mp_channel_create+0x7d/0x150 net/bluetooth/a2mp.c:894
l2cap_data_channel net/bluetooth/l2cap_core.c:7571 [inline]
l2cap_recv_frame+0x48e3/0x8d90 net/bluetooth/l2cap_core.c:7726
l2cap_recv_acldata+0xaa6/0xc00 net/bluetooth/l2cap_core.c:8431
hci_acldata_packet net/bluetooth/hci_core.c:3793 [inline]
hci_rx_work+0x705/0x1230 net/bluetooth/hci_core.c:4028
process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Freed by task 49:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
kasan_set_track+0x21/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2a/0x40 mm/kasan/generic.c:511
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1669 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1695
slab_free mm/slub.c:3599 [inline]
__kmem_cache_free+0xab/0x3b0 mm/slub.c:3612
l2cap_chan_destroy net/bluetooth/l2cap_core.c:509 [inline]
kref_put include/linux/kref.h:65 [inline]
l2cap_chan_put+0x22a/0x2d0 net/bluetooth/l2cap_core.c:533
l2cap_conn_del+0x3fc/0x7b0 net/bluetooth/l2cap_core.c:1930
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:8214 [inline]
l2cap_disconn_cfm+0x8c/0xc0 net/bluetooth/l2cap_core.c:8207
hci_disconn_cfm include/net/bluetooth/hci_core.h:1787 [inline]
hci_conn_hash_flush+0x122/0x260 net/bluetooth/hci_conn.c:2430
hci_dev_close_sync+0x5c4/0x1200 net/bluetooth/hci_sync.c:4804
hci_dev_do_close+0x2d/0x70 net/bluetooth/hci_core.c:554
hci_error_reset+0x9e/0x140 net/bluetooth/hci_core.c:1059
process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Last potentially related work creation:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
call_rcu+0x99/0x820 kernel/rcu/tree.c:2796
netlink_release+0xeff/0x1db0 net/netlink/af_netlink.c:815
__sock_release+0xcd/0x280 net/socket.c:650
sock_close+0x18/0x20 net/socket.c:1365
__fput+0x27c/0xa90 fs/file_table.c:320
task_work_run+0x16b/0x270 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203
__syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:296
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888020ab3000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1208 bytes inside of
2048-byte region [ffff888020ab3000, ffff888020ab3800)

The buggy address belongs to the physical page:
page:ffffea000082ac00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x20ab0
head:ffffea000082ac00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffff888011842000 dead000080080008 0000000000000000
raw: 0000000000000000 dead000000000001 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 8393630899, free_ts 0
prep_new_page mm/page_alloc.c:2538 [inline]
get_page_from_freelist+0x1092/0x2d20 mm/page_alloc.c:4287
__alloc_pages+0x1c7/0x5a0 mm/page_alloc.c:5546
alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2113
alloc_pages+0x22f/0x270 mm/mempolicy.c:2275
alloc_slab_page mm/slub.c:1739 [inline]
allocate_slab+0x213/0x300 mm/slub.c:1884
new_slab mm/slub.c:1937 [inline]
___slab_alloc+0xac1/0x1430 mm/slub.c:3119
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3217
slab_alloc_node mm/slub.c:3302 [inline]
__kmem_cache_alloc_node+0x18a/0x3d0 mm/slub.c:3375
__do_kmalloc_node mm/slab_common.c:933 [inline]
__kmalloc+0x44/0xc0 mm/slab_common.c:947
kmalloc include/linux/slab.h:564 [inline]
kzalloc include/linux/slab.h:695 [inline]
rfkill_alloc+0xa6/0x2c0 net/rfkill/core.c:984
wiphy_new_nm+0x12d5/0x2090 net/wireless/core.c:527
wiphy_new include/net/cfg80211.h:5550 [inline]
virt_wifi_make_wiphy drivers/net/wireless/virt_wifi.c:363 [inline]
virt_wifi_init_module+0x64/0x3d6 drivers/net/wireless/virt_wifi.c:665
do_one_initcall+0x13d/0x780 init/main.c:1307
do_initcall_level init/main.c:1382 [inline]
do_initcalls init/main.c:1398 [inline]
do_basic_setup init/main.c:1417 [inline]
kernel_init_freeable+0x6ff/0x788 init/main.c:1637
kernel_init+0x1a/0x1d0 init/main.c:1525
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page_owner free stack trace missing

Memory state around the buggy address:
ffff888020ab3380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888020ab3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888020ab3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888020ab3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888020ab3580: 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.
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syzbot can test patches for this issue, for details see:
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Hillf Danton

unread,
Oct 23, 2022, 4:30:09 AMOct 23
to syzbot, linux-...@vger.kernel.org, linu...@kvack.org, syzkall...@googlegroups.com
On 26 Sep 2022 09:43:42 -0700
> syzbot found the following issue on:
>
> HEAD commit: aaa11ce2ffc8 Add linux-next specific files for 20220923
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14b32754880000
> kernel config: https://syzkaller.appspot.com/x/.config?x=186d1ff305f10294
> dashboard link: https://syzkaller.appspot.com/bug?extid=03450dacbc626061c3a3
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12d389c4880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14269e38880000

Put refcount in balance for channel in bid to fix uaf.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git aaa11ce2ffc8

--- a/net/bluetooth/a2mp.c
+++ b/net/bluetooth/a2mp.c
@@ -896,6 +896,8 @@ struct l2cap_chan *a2mp_channel_create(s
BT_ERR("Could not create AMP manager");
return NULL;
}
+ /* pair with put in l2cap_data_channel() */
+ l2cap_chan_hold(mgr->a2mp_chan);

BT_DBG("mgr: %p chan %p", mgr, mgr->a2mp_chan);

--

syzbot

unread,
Oct 23, 2022, 11:43:20 AMOct 23
to hda...@sina.com, linux-...@vger.kernel.org, linu...@kvack.org, syzkall...@googlegroups.com
Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+03450d...@syzkaller.appspotmail.com

Tested on:

commit: aaa11ce2 Add linux-next specific files for 20220923
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=172b6de2880000
kernel config: https://syzkaller.appspot.com/x/.config?x=186d1ff305f10294
dashboard link: https://syzkaller.appspot.com/bug?extid=03450dacbc626061c3a3
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch: https://syzkaller.appspot.com/x/patch.diff?x=1069544a880000

Note: testing is done by a robot and is best-effort only.
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