Bluetooth: Fix race condition with L2CAP information request

When two L2CAP connections are requested quickly after the ACL link has
been established there exists a window for a race condition where a
connection request is sent before the information response has been
received. Any connection request should only be sent after an exchange
of the extended features mask has been finished.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

2 files changed, 16 insertions, 4 deletions

diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 29f720e6188a..1c8cf3e9b1ca 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -223,7 +223,8 @@ struct l2cap_conn {
 };
 
 #define L2CAP_INFO_CL_MTU_REQ_SENT      0x01
-#define L2CAP_INFO_FEAT_MASK_REQ_SENT   0x02
+#define L2CAP_INFO_FEAT_MASK_REQ_SENT   0x04
+#define L2CAP_INFO_FEAT_MASK_REQ_DONE   0x08
 
 /* ----- L2CAP channel and socket info ----- */
 #define l2cap_pi(sk) ((struct l2cap_pinfo *) sk)
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 8a93dde4095b..07fdbc7dd54d 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -320,6 +320,9 @@ static void l2cap_do_start(struct sock *sk)
         struct l2cap_conn *conn = l2cap_pi(sk)->conn;
 
         if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT) {
+                if (!(conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE))
+                        return;
+
                 if (l2cap_check_security(sk)) {
                         struct l2cap_conn_req req;
                         req.scid = cpu_to_le16(l2cap_pi(sk)->scid);
@@ -455,6 +458,8 @@ static void l2cap_info_timeout(unsigned long arg)
 
         conn->info_ident = 0;
 
+        conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
+
         l2cap_conn_start(conn);
 }
 
@@ -1787,6 +1792,9 @@ static inline int l2cap_command_rej(struct l2cap_conn *conn, struct l2cap_cmd_hd
                                         cmd->ident == conn->info_ident) {
                 conn->info_ident = 0;
                 del_timer(&conn->info_timer);
+
+                conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
+
                 l2cap_conn_start(conn);
         }
 
@@ -1857,7 +1865,7 @@ static inline int l2cap_connect_req(struct l2cap_conn *conn, struct l2cap_cmd_hd
 
         l2cap_pi(sk)->ident = cmd->ident;
 
-        if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT) {
+        if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE) {
                 if (l2cap_check_security(sk)) {
                         if (bt_sk(sk)->defer_setup) {
                                 sk->sk_state = BT_CONNECT2;
@@ -2176,10 +2184,13 @@ static inline int l2cap_information_rsp(struct l2cap_conn *conn, struct l2cap_cm
 
         del_timer(&conn->info_timer);
 
-        if (type == L2CAP_IT_FEAT_MASK)
+        if (type == L2CAP_IT_FEAT_MASK) {
                 conn->feat_mask = get_unaligned_le32(rsp->data);
 
-        l2cap_conn_start(conn);
+                conn->info_state |= L2CAP_INFO_FEAT_MASK_REQ_DONE;
+
+                l2cap_conn_start(conn);
+        }
 
         return 0;
 }