mac80211: validate TIM IE length

The TIM IE must not be shorter than 4 bytes, so verify that
when parsing it.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index dc60804d6dd0..1619e0cd26e2 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -441,6 +441,9 @@ static bool ieee80211_check_tim(struct ieee802_11_elems *elems, u16 aid)
         u8 index, indexn1, indexn2;
         struct ieee80211_tim_ie *tim = (struct ieee80211_tim_ie *) elems->tim;
 
+        if (unlikely(!tim || elems->tim_len < 4))
+                return false;
+
         aid &= 0x3fff;
         index = aid / 8;
         mask  = 1 << (aid & 7);