[PATCH 2/2] mwifiex: Fix heap overflow in mwifiex_uap_parse_tail_ies()

[Tyler Hicks]

From: Takashi Iwai <tiwai at suse.de>

A few places in mwifiex_uap_parse_tail_ies() perform memcpy()
unconditionally, which may lead to either buffer overflow or read over
boundary.

This patch addresses the issues by checking the read size and the
destination size at each place more properly.  Along with the fixes,
the patch cleans up the code slightly by introducing a temporary
variable for the token size, and unifies the error path with the
standard goto statement.

Reported-by: huangwen <huangwen at venustech.com.cn>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Kalle Valo <kvalo at codeaurora.org>

CVE-2019-10126

(cherry picked from commit 69ae4f6aac1578575126319d3f55550e7e440449)
Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
 drivers/net/wireless/marvell/mwifiex/ie.c | 47 ++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/ie.c b/drivers/net/wireless/marvell/mwifiex/ie.c
index 6845eb57b39a..653d347a9a19 100644
--- a/drivers/net/wireless/marvell/mwifiex/ie.c
+++ b/drivers/net/wireless/marvell/mwifiex/ie.c
@@ -329,6 +329,8 @@ static int mwifiex_uap_parse_tail_ies(struct mwifiex_private *priv,
 	struct ieee80211_vendor_ie *vendorhdr;
 	u16 gen_idx = MWIFIEX_AUTO_IDX_MASK, ie_len = 0;
 	int left_len, parsed_len = 0;
+	unsigned int token_len;
+	int err = 0;
 
 	if (!info->tail || !info->tail_len)
 		return 0;
@@ -344,6 +346,12 @@ static int mwifiex_uap_parse_tail_ies(struct mwifiex_private *priv,
 	 */
 	while (left_len > sizeof(struct ieee_types_header)) {
 		hdr = (void *)(info->tail + parsed_len);
+		token_len = hdr->len + sizeof(struct ieee_types_header);
+		if (token_len > left_len) {
+			err = -EINVAL;
+			goto out;
+		}
+
 		switch (hdr->element_id) {
 		case WLAN_EID_SSID:
 		case WLAN_EID_SUPP_RATES:
@@ -361,17 +369,20 @@ static int mwifiex_uap_parse_tail_ies(struct mwifiex_private *priv,
 			if (cfg80211_find_vendor_ie(WLAN_OUI_MICROSOFT,
 						    WLAN_OUI_TYPE_MICROSOFT_WMM,
 						    (const u8 *)hdr,
-						    hdr->len + sizeof(struct ieee_types_header)))
+						    token_len))
 				break;
 			/* fall through */
 		default:
-			memcpy(gen_ie->ie_buffer + ie_len, hdr,
-			       hdr->len + sizeof(struct ieee_types_header));
-			ie_len += hdr->len + sizeof(struct ieee_types_header);
+			if (ie_len + token_len > IEEE_MAX_IE_SIZE) {
+				err = -EINVAL;
+				goto out;
+			}
+			memcpy(gen_ie->ie_buffer + ie_len, hdr, token_len);
+			ie_len += token_len;
 			break;
 		}
-		left_len -= hdr->len + sizeof(struct ieee_types_header);
-		parsed_len += hdr->len + sizeof(struct ieee_types_header);
+		left_len -= token_len;
+		parsed_len += token_len;
 	}
 
 	/* parse only WPA vendor IE from tail, WMM IE is configured by
@@ -381,15 +392,17 @@ static int mwifiex_uap_parse_tail_ies(struct mwifiex_private *priv,
 						    WLAN_OUI_TYPE_MICROSOFT_WPA,
 						    info->tail, info->tail_len);
 	if (vendorhdr) {
-		memcpy(gen_ie->ie_buffer + ie_len, vendorhdr,
-		       vendorhdr->len + sizeof(struct ieee_types_header));
-		ie_len += vendorhdr->len + sizeof(struct ieee_types_header);
+		token_len = vendorhdr->len + sizeof(struct ieee_types_header);
+		if (ie_len + token_len > IEEE_MAX_IE_SIZE) {
+			err = -EINVAL;
+			goto out;
+		}
+		memcpy(gen_ie->ie_buffer + ie_len, vendorhdr, token_len);
+		ie_len += token_len;
 	}
 
-	if (!ie_len) {
-		kfree(gen_ie);
-		return 0;
-	}
+	if (!ie_len)
+		goto out;
 
 	gen_ie->ie_index = cpu_to_le16(gen_idx);
 	gen_ie->mgmt_subtype_mask = cpu_to_le16(MGMT_MASK_BEACON |
@@ -399,13 +412,15 @@ static int mwifiex_uap_parse_tail_ies(struct mwifiex_private *priv,
 
 	if (mwifiex_update_uap_custom_ie(priv, gen_ie, &gen_idx, NULL, NULL,
 					 NULL, NULL)) {
-		kfree(gen_ie);
-		return -1;
+		err = -EINVAL;
+		goto out;
 	}
 
 	priv->gen_idx = gen_idx;
+
+ out:
 	kfree(gen_ie);
-	return 0;
+	return err;
 }
 
 /* This function parses different IEs-head & tail IEs, beacon IEs,
-- 
2.7.4