[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

(backported from commit 69ae4f6aac1578575126319d3f55550e7e440449)
[tyhicks: Backport to Xenial:
 - There's no need to adjust the WLAN_EID_VENDOR_SPECIFIC case due to
   missing commit bfc83ea196ad ("mwifiex: Fix skipped vendor specific
   IEs")
 - Adjust file path due to missing commit 277b024e5e3d ("mwifiex: move
   under marvell vendor directory")]
Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
 drivers/net/wireless/mwifiex/ie.c | 45 ++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 15 deletions(-)

diff --git a/drivers/net/wireless/mwifiex/ie.c b/drivers/net/wireless/mwifiex/ie.c
index c488c3068abc..0f977dc556ca 100644
--- a/drivers/net/wireless/mwifiex/ie.c
+++ b/drivers/net/wireless/mwifiex/ie.c
@@ -328,6 +328,8 @@ 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;
@@ -343,6 +345,12 @@ 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:
@@ -356,13 +364,16 @@ static int mwifiex_uap_parse_tail_ies(struct mwifiex_private *priv,
 		case WLAN_EID_VENDOR_SPECIFIC:
 			break;
 		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
@@ -372,15 +383,17 @@ 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 |
@@ -390,13 +403,15 @@ 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