[PATCH v2 2/2] Bluetooth: SCO: Fix data-race on sco_pi fields in sco_connect

[SeungJu Cheon]

sco_sock_connect() copies the destination address into sco_pi(sk)->dst
under lock_sock(), then releases the lock and calls sco_connect(),
which reads dst, src, setting, and codec without holding lock_sock() in
hci_get_route() and hci_connect_sco().

These fields may be modified concurrently by connect(), bind(), or
setsockopt() on the same socket, resulting in data-races reported by
KCSAN.

Fix this by snapshotting dst, src, setting, and codec under lock_sock()
at the start of sco_connect() before passing them to hci_get_route()
and hci_connect_sco().

BUG: KCSAN: data-race in memcmp+0x45/0xb0

race at unknown origin, with read to 0xffff88800e6b0dd0 of 1 bytes
by task 315 on cpu 0:
 memcmp+0x45/0xb0
 hci_connect_acl+0x1b7/0x6b0
 hci_connect_sco+0x4d/0xb30
 sco_sock_connect+0x27b/0xd60
 __sys_connect_file+0xbd/0xe0
 __sys_connect+0xe0/0x110
 __x64_sys_connect+0x40/0x50
 x64_sys_call+0xcad/0x1c60
 do_syscall_64+0x133/0x590
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: 9a8ec9e8ebb5 ("Bluetooth: SCO: Fix possible circular locking dependency on sco_connect_cfm")
Signed-off-by: SeungJu Cheon <suunj1331@xxxxxxxxx>
---
 net/bluetooth/sco.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index f1799c6a6f87..140869e5b2df 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -312,11 +312,21 @@ static int sco_connect(struct sock *sk)
 	struct sco_conn *conn;
 	struct hci_conn *hcon;
 	struct hci_dev  *hdev;
+	bdaddr_t src, dst;
+	struct bt_codec codec;
+	__u16 setting;
 	int err, type;
 
-	BT_DBG("%pMR -> %pMR", &sco_pi(sk)->src, &sco_pi(sk)->dst);
+	lock_sock(sk);
+	bacpy(&src, &sco_pi(sk)->src);
+	bacpy(&dst, &sco_pi(sk)->dst);
+	setting = sco_pi(sk)->setting;
+	codec = sco_pi(sk)->codec;
+	release_sock(sk);
+
+	BT_DBG("%pMR -> %pMR", &src, &dst);
 
-	hdev = hci_get_route(&sco_pi(sk)->dst, &sco_pi(sk)->src, BDADDR_BREDR);
+	hdev = hci_get_route(&dst, &src, BDADDR_BREDR);
 	if (!hdev)
 		return -EHOSTUNREACH;
 
@@ -327,7 +337,7 @@ static int sco_connect(struct sock *sk)
 	else
 		type = SCO_LINK;
 
-	switch (sco_pi(sk)->setting & SCO_AIRMODE_MASK) {
+	switch (setting & SCO_AIRMODE_MASK) {
 	case SCO_AIRMODE_TRANSP:
 		if (!lmp_transp_capable(hdev) || !lmp_esco_capable(hdev)) {
 			err = -EOPNOTSUPP;
@@ -336,8 +346,8 @@ static int sco_connect(struct sock *sk)
 		break;
 	}
 
-	hcon = hci_connect_sco(hdev, type, &sco_pi(sk)->dst,
-			       sco_pi(sk)->setting, &sco_pi(sk)->codec,
+	hcon = hci_connect_sco(hdev, type, &dst,
+			       setting, &codec,
 			       READ_ONCE(sk->sk_sndtimeo));
 	if (IS_ERR(hcon)) {
 		err = PTR_ERR(hcon);
-- 
2.52.0