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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
To:     linux-bluetooth@vger.kernel.org
Subject: [PATCH] Bluetooth: eir: Fix using strlen with hdev->{dev_name,short_name}
Date:   Tue, 24 May 2022 13:25:48 -0700
Message-Id: <20220524202548.3569218-1-luiz.dentz@gmail.com>
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From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Both dev_name and short_name are not guaranteed to be NULL terminated so
this instead use strnlen and then attempt to determine if the resulting
string needs to be truncated or not.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216018
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/eir.c | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/net/bluetooth/eir.c b/net/bluetooth/eir.c
index 7e930f77ecab..4171edee88e4 100644
--- a/net/bluetooth/eir.c
+++ b/net/bluetooth/eir.c
@@ -13,6 +13,20 @@
 
 #define PNP_INFO_SVCLASS_ID		0x1200
 
+static u8 eir_append_name(u8 *eir, u16 eir_len, u8 type, u8 *data, u8 data_len)
+{
+	u8 name[HCI_MAX_SHORT_NAME_LENGTH + 1];
+
+	/* If data is already NULL terminated just pass it directly */
+	if (data[data_len - 1] == '\0')
+		return eir_append_data(eir, eir_len, type, data, data_len);
+
+	memcpy(name, data, HCI_MAX_SHORT_NAME_LENGTH);
+	name[HCI_MAX_SHORT_NAME_LENGTH] = '\0';
+
+	return eir_append_data(eir, eir_len, type, name, sizeof(name));
+}
+
 u8 eir_append_local_name(struct hci_dev *hdev, u8 *ptr, u8 ad_len)
 {
 	size_t short_len;
@@ -23,29 +37,26 @@ u8 eir_append_local_name(struct hci_dev *hdev, u8 *ptr, u8 ad_len)
 		return ad_len;
 
 	/* use complete name if present and fits */
-	complete_len = strlen(hdev->dev_name);
+	complete_len = strnlen(hdev->dev_name, sizeof(hdev->dev_name));
 	if (complete_len && complete_len <= HCI_MAX_SHORT_NAME_LENGTH)
-		return eir_append_data(ptr, ad_len, EIR_NAME_COMPLETE,
+		return eir_append_name(ptr, ad_len, EIR_NAME_COMPLETE,
 				       hdev->dev_name, complete_len + 1);
 
 	/* use short name if present */
-	short_len = strlen(hdev->short_name);
+	short_len = strnlen(hdev->short_name, sizeof(hdev->short_name));
 	if (short_len)
-		return eir_append_data(ptr, ad_len, EIR_NAME_SHORT,
-				       hdev->short_name, short_len + 1);
+		return eir_append_name(ptr, ad_len, EIR_NAME_SHORT,
+				       hdev->short_name,
+				       short_len == HCI_MAX_SHORT_NAME_LENGTH ?
+				       short_len : short_len + 1);
 
 	/* use shortened full name if present, we already know that name
 	 * is longer then HCI_MAX_SHORT_NAME_LENGTH
 	 */
-	if (complete_len) {
-		u8 name[HCI_MAX_SHORT_NAME_LENGTH + 1];
-
-		memcpy(name, hdev->dev_name, HCI_MAX_SHORT_NAME_LENGTH);
-		name[HCI_MAX_SHORT_NAME_LENGTH] = '\0';
-
-		return eir_append_data(ptr, ad_len, EIR_NAME_SHORT, name,
-				       sizeof(name));
-	}
+	if (complete_len)
+		return eir_append_name(ptr, ad_len, EIR_NAME_SHORT,
+				       hdev->dev_name,
+				       HCI_MAX_SHORT_NAME_LENGTH);
 
 	return ad_len;
 }
@@ -168,7 +179,7 @@ void eir_create(struct hci_dev *hdev, u8 *data)
 	u8 *ptr = data;
 	size_t name_len;
 
-	name_len = strlen(hdev->dev_name);
+	name_len = strnlen(hdev->dev_name, sizeof(hdev->dev_name));
 
 	if (name_len > 0) {
 		/* EIR Data type */
-- 
2.35.1