p54: fix eeprom parser length sanity checks

When I called p54_parse_eeprom() on a hand-coded structure
I managed to make a small mistake with wrap->len which caused
a segfault a few lines down when trying to read entry->len.
This patch changes the validation code to avoid such problems.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Tested-by: Florian Fainelli <florian.fainelli@telecomint.eu>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/net/wireless/p54common.c b/drivers/net/wireless/p54common.c
index 56aabec73c20..d191e055a788 100644
--- a/drivers/net/wireless/p54common.c
+++ b/drivers/net/wireless/p54common.c
@@ -166,18 +166,23 @@ int p54_parse_eeprom(struct ieee80211_hw *dev, void *eeprom, int len)
         struct p54_common *priv = dev->priv;
         struct eeprom_pda_wrap *wrap = NULL;
         struct pda_entry *entry;
-        int i = 0;
         unsigned int data_len, entry_len;
         void *tmp;
         int err;
+        u8 *end = (u8 *)eeprom + len;
 
         wrap = (struct eeprom_pda_wrap *) eeprom;
         entry = (void *)wrap->data + le16_to_cpu(wrap->len);
-        i += 2;
-        i += le16_to_cpu(entry->len)*2;
-        while (i < len) {
+
+        /* verify that at least the entry length/code fits */
+        while ((u8 *)entry <= end - sizeof(*entry)) {
                 entry_len = le16_to_cpu(entry->len);
                 data_len = ((entry_len - 1) << 1);
+
+                /* abort if entry exceeds whole structure */
+                if ((u8 *)entry + sizeof(*entry) + data_len > end)
+                        break;
+
                 switch (le16_to_cpu(entry->code)) {
                 case PDR_MAC_ADDRESS:
                         SET_IEEE80211_PERM_ADDR(dev, entry->data);
@@ -249,13 +254,12 @@ int p54_parse_eeprom(struct ieee80211_hw *dev, void *eeprom, int len)
                         priv->version = *(u8 *)(entry->data + 1);
                         break;
                 case PDR_END:
-                        i = len;
+                        /* make it overrun */
+                        entry_len = len;
                         break;
                 }
 
                 entry = (void *)entry + (entry_len + 1)*2;
-                i += 2;
-                i += entry_len*2;
         }
 
         if (!priv->iq_autocal || !priv->output_limit || !priv->curve_data) {