Bluetooth: qca: fix info leak when fetching fw build id

Add the missing sanity checks and move the 255-byte build-id buffer off
the stack to avoid leaking stack data through debugfs in case the
build-info reply is malformed.

Fixes: c0187b0b ("Bluetooth: btqca: Add support to read FW build version for WCN3991 BTSoC")
Cc: stable@vger.kernel.org	# 5.12
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/bluetooth/btqca.c

@@ -99,7 +99,8 @@ static int qca_read_fw_build_info(struct hci_dev *hdev)
 {
 	struct sk_buff *skb;
 	struct edl_event_hdr *edl;
-	char cmd, build_label[QCA_FW_BUILD_VER_LEN];
+	char *build_label;
+	char cmd;
 	int build_lbl_len, err = 0;
 
 	bt_dev_dbg(hdev, "QCA read fw build info");
@@ -114,6 +115,11 @@ static int qca_read_fw_build_info(struct hci_dev *hdev)
 		return err;
 	}
 
+	if (skb->len < sizeof(*edl)) {
+		err = -EILSEQ;
+		goto out;
+	}
+
 	edl = (struct edl_event_hdr *)(skb->data);
 	if (!edl) {
 		bt_dev_err(hdev, "QCA read fw build info with no header");
@@ -129,14 +135,25 @@ static int qca_read_fw_build_info(struct hci_dev *hdev)
 		goto out;
 	}
 
+	if (skb->len < sizeof(*edl) + 1) {
+		err = -EILSEQ;
+		goto out;
+	}
+
 	build_lbl_len = edl->data[0];
-	if (build_lbl_len <= QCA_FW_BUILD_VER_LEN - 1) {
-		memcpy(build_label, edl->data + 1, build_lbl_len);
-		*(build_label + build_lbl_len) = '\0';
+
+	if (skb->len < sizeof(*edl) + 1 + build_lbl_len) {
+		err = -EILSEQ;
+		goto out;
 	}
 
+	build_label = kstrndup(&edl->data[1], build_lbl_len, GFP_KERNEL);
+	if (!build_label)
+		goto out;
+
 	hci_set_fw_info(hdev, "%s", build_label);
 
+	kfree(build_label);
 out:
 	kfree_skb(skb);
 	return err;

drivers/bluetooth/btqca.h

@@ -48,7 +48,6 @@
 #define get_soc_ver(soc_id, rom_ver)	\
 	((le32_to_cpu(soc_id) << 16) | (le16_to_cpu(rom_ver)))
 
-#define QCA_FW_BUILD_VER_LEN		255
 #define QCA_HSP_GF_SOC_ID			0x1200
 #define QCA_HSP_GF_SOC_MASK			0x0000ff00