[PATCH v1 1/2] Bluetooth: ISO: Fix data-race on iso_pi fields in hci_get_route calls

[SeungJu Cheon]

iso_connect_bis(), iso_connect_cis(), iso_listen_bis(), and
iso_conn_big_sync() all call hci_get_route() reading iso_pi(sk)->dst,
iso_pi(sk)->src, and iso_pi(sk)->src_type without holding lock_sock.

These fields can be concurrently written by another thread calling
connect() or setsockopt() on the same socket, leading to torn reads
or TOCTOU mismatches.

Fix by snapshotting dst, src, and src_type into local variables under
lock_sock before calling hci_get_route() in all four functions.

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

race at unknown origin, with read to 0xffff8880122135cf of 1 bytes by task 333 on cpu 1:
 memcmp+0x45/0xb0
 hci_get_route+0x27e/0x490
 iso_connect_cis+0x4c/0xa10
 iso_sock_connect+0x60e/0xb30
 __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: 241f51931c35 ("Bluetooth: ISO: Avoid circular locking dependency")
Signed-off-by: SeungJu Cheon <suunj1331@xxxxxxxxx>
---
 net/bluetooth/iso.c | 51 ++++++++++++++++++++++++++++++++++-----------
 1 file changed, 39 insertions(+), 12 deletions(-)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index d7af617cda45..58bb3a10d49f 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -337,12 +337,19 @@ static int iso_connect_bis(struct sock *sk)
 	struct iso_conn *conn;
 	struct hci_conn *hcon;
 	struct hci_dev  *hdev;
+	bdaddr_t src, dst;
+	u8 src_type;
 	int err;
 
-	BT_DBG("%pMR (SID 0x%2.2x)", &iso_pi(sk)->src, iso_pi(sk)->bc_sid);
+	lock_sock(sk);
+	bacpy(&dst, &iso_pi(sk)->dst);
+	bacpy(&src, &iso_pi(sk)->src);
+	src_type = iso_pi(sk)->src_type;
+	release_sock(sk);
+
+	BT_DBG("%pMR (SID 0x%2.2x)", &src, iso_pi(sk)->bc_sid);
 
-	hdev = hci_get_route(&iso_pi(sk)->dst, &iso_pi(sk)->src,
-			     iso_pi(sk)->src_type);
+	hdev = hci_get_route(&dst, &src, src_type);
 	if (!hdev)
 		return -EHOSTUNREACH;
 
@@ -430,12 +437,19 @@ static int iso_connect_cis(struct sock *sk)
 	struct iso_conn *conn;
 	struct hci_conn *hcon;
 	struct hci_dev  *hdev;
+	bdaddr_t src, dst;
+	u8 src_type;
 	int err;
 
-	BT_DBG("%pMR -> %pMR", &iso_pi(sk)->src, &iso_pi(sk)->dst);
+	lock_sock(sk);
+	bacpy(&dst, &iso_pi(sk)->dst);
+	bacpy(&src, &iso_pi(sk)->src);
+	src_type = iso_pi(sk)->src_type;
+	release_sock(sk);
+
+	BT_DBG("%pMR -> %pMR", &src, &dst);
 
-	hdev = hci_get_route(&iso_pi(sk)->dst, &iso_pi(sk)->src,
-			     iso_pi(sk)->src_type);
+	hdev = hci_get_route(&dst, &src, src_type);
 	if (!hdev)
 		return -EHOSTUNREACH;
 
@@ -1210,11 +1224,18 @@ static int iso_listen_bis(struct sock *sk)
 {
 	struct hci_dev *hdev;
 	int err = 0;
+	bdaddr_t src, dst;
+	u8 src_type;
 	struct iso_conn *conn;
 	struct hci_conn *hcon;
 
-	BT_DBG("%pMR -> %pMR (SID 0x%2.2x)", &iso_pi(sk)->src,
-	       &iso_pi(sk)->dst, iso_pi(sk)->bc_sid);
+	lock_sock(sk);
+	bacpy(&dst, &iso_pi(sk)->dst);
+	bacpy(&src, &iso_pi(sk)->src);
+	src_type = iso_pi(sk)->src_type;
+	release_sock(sk);
+
+	BT_DBG("%pMR -> %pMR (SID 0x%2.2x)", &src, &dst, iso_pi(sk)->bc_sid);
 
 	write_lock(&iso_sk_list.lock);
 
@@ -1227,8 +1248,7 @@ static int iso_listen_bis(struct sock *sk)
 	if (err)
 		return err;
 
-	hdev = hci_get_route(&iso_pi(sk)->dst, &iso_pi(sk)->src,
-			     iso_pi(sk)->src_type);
+	hdev = hci_get_route(&dst, &src, src_type);
 	if (!hdev)
 		return -EHOSTUNREACH;
 
@@ -1564,9 +1584,16 @@ static void iso_conn_big_sync(struct sock *sk)
 {
 	int err;
 	struct hci_dev *hdev;
+	bdaddr_t src, dst;
+	u8 src_type;
+
+	lock_sock(sk);
+	bacpy(&dst, &iso_pi(sk)->dst);
+	bacpy(&src, &iso_pi(sk)->src);
+	src_type = iso_pi(sk)->src_type;
+	release_sock(sk);
 
-	hdev = hci_get_route(&iso_pi(sk)->dst, &iso_pi(sk)->src,
-			     iso_pi(sk)->src_type);
+	hdev = hci_get_route(&dst, &src, src_type);
 
 	if (!hdev)
 		return;
-- 
2.52.0