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Message-ID: <tencent_7697B4E9DEEC52CEB478626D182DE96CB00A@qq.com>
Date: Sun,  8 Sep 2024 15:22:28 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+c12e2f941af1feb5632c@...kaller.appspotmail.com
Cc: johan.hedberg@...il.com,
	linux-bluetooth@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	luiz.dentz@...il.com,
	marcel@...tmann.org,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] Bluetooth/l2cap: Fix uaf in l2cap_connect

[Syzbot reported]
BUG: KASAN: slab-use-after-free in l2cap_connect.constprop.0+0x10d8/0x1270 net/bluetooth/l2cap_core.c:3949
Read of size 8 at addr ffff8880241e9800 by task kworker/u9:0/54

CPU: 0 UID: 0 PID: 54 Comm: kworker/u9:0 Not tainted 6.11.0-rc6-syzkaller-00268-g788220eee30d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: hci2 hci_rx_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:488
 kasan_report+0xd9/0x110 mm/kasan/report.c:601
 l2cap_connect.constprop.0+0x10d8/0x1270 net/bluetooth/l2cap_core.c:3949
 l2cap_connect_req net/bluetooth/l2cap_core.c:4080 [inline]
 l2cap_bredr_sig_cmd net/bluetooth/l2cap_core.c:4772 [inline]
 l2cap_sig_channel net/bluetooth/l2cap_core.c:5543 [inline]
 l2cap_recv_frame+0xf0b/0x8eb0 net/bluetooth/l2cap_core.c:6825
 l2cap_recv_acldata+0x9b4/0xb70 net/bluetooth/l2cap_core.c:7514
 hci_acldata_packet net/bluetooth/hci_core.c:3791 [inline]
 hci_rx_work+0xaab/0x1610 net/bluetooth/hci_core.c:4028
 process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
...

Freed by task 5245:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
 poison_slab_object+0xf7/0x160 mm/kasan/common.c:240
 __kasan_slab_free+0x32/0x50 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2256 [inline]
 slab_free mm/slub.c:4477 [inline]
 kfree+0x12a/0x3b0 mm/slub.c:4598
 l2cap_conn_free net/bluetooth/l2cap_core.c:1810 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_conn_put net/bluetooth/l2cap_core.c:1822 [inline]
 l2cap_conn_del+0x59d/0x730 net/bluetooth/l2cap_core.c:1802
 l2cap_connect_cfm+0x9e6/0xf80 net/bluetooth/l2cap_core.c:7241
 hci_connect_cfm include/net/bluetooth/hci_core.h:1960 [inline]
 hci_conn_failed+0x1c3/0x370 net/bluetooth/hci_conn.c:1265
 hci_abort_conn_sync+0x75a/0xb50 net/bluetooth/hci_sync.c:5583
 abort_conn_sync+0x197/0x360 net/bluetooth/hci_conn.c:2917
 hci_cmd_sync_work+0x1a4/0x410 net/bluetooth/hci_sync.c:328
 process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

[Analysis] 
There was a data race when accessing conn in hci_rx_work and hci_cmd_sync_work.
This is because the hci dev lock was prematurely exited when executing
hci_acldata_macket() in hci_rx_work, which resulted in it being released
by hci_cmd_sync_work when accessing conn outside the lock.

Reported-and-tested-by: syzbot+c12e2f941af1feb5632c@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c12e2f941af1feb5632c
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 net/bluetooth/hci_core.c   | 3 ++-
 net/bluetooth/l2cap_core.c | 2 --
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index f25a21f532aa..4f7b45bb863f 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3776,18 +3776,19 @@ static void hci_acldata_packet(struct hci_dev *hdev, struct sk_buff *skb)
 
 	hci_dev_lock(hdev);
 	conn = hci_conn_hash_lookup_handle(hdev, handle);
-	hci_dev_unlock(hdev);
 
 	if (conn) {
 		hci_conn_enter_active_mode(conn, BT_POWER_FORCE_ACTIVE_OFF);
 
 		/* Send to upper protocol */
 		l2cap_recv_acldata(conn, skb, flags);
+		hci_dev_unlock(hdev);
 		return;
 	} else {
 		bt_dev_err(hdev, "ACL packet for unknown connection handle %d",
 			   handle);
 	}
+	hci_dev_unlock(hdev);
 
 	kfree_skb(skb);
 }
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 9988ba382b68..b948b0a3b2f2 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4072,10 +4072,8 @@ static int l2cap_connect_req(struct l2cap_conn *conn,
 	if (cmd_len < sizeof(struct l2cap_conn_req))
 		return -EPROTO;
 
-	hci_dev_lock(hdev);
 	if (hci_dev_test_flag(hdev, HCI_MGMT))
 		mgmt_device_connected(hdev, hcon, NULL, 0);
-	hci_dev_unlock(hdev);
 
 	l2cap_connect(conn, cmd, data, L2CAP_CONN_RSP);
 	return 0;
-- 
2.43.0


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