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>

diff --git a/drivers/net/wireless/p54common.c b/drivers/net/wireless/p54common.c
index 56aabec73c201ba5cd48b481f59a83a98cb0e6e7..d191e055a788210e4a2b6343f4815b1bf120180d 100644 (file)
--- 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) {