[PATCH 2.6.30!] mac80211: validate TIM IE length

Johannes Berg
2009-04-16T22:18:45Z

when parsing it and use the proper type. To ease that adjust
struct ieee80211_tim_ie to have a virtual bitmap of size
at least 1.

Also check that the TIM IE is actually present before trying
to parse it!

Because other people may need the function, make it a static
inline in ieee80211.h.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
---
I can provide a shorter fix for 2.6.30 if required.

Kalle!!

include/linux/ieee80211.h | 32 +++++++++++++++++++++++++++++++-
net/mac80211/ieee80211_i.h | 2 +-
net/mac80211/mlme.c | 24 ++----------------------
net/mac80211/util.c | 6 ++++--
4 files changed, 38 insertions(+), 26 deletions(-)

--- wireless-testing.orig/include/linux/ieee80211.h 2009-04-16 23:56:05.000000000 +0200
+++ wireless-testing/include/linux/ieee80211.h 2009-04-17 00:09:21.000000000 +0200
@@ -540,7 +540,7 @@ struct ieee80211_tim_ie {
u8 dtim_period;
u8 bitmap_ctrl;
/* variable size: 1 - 251 bytes */
- u8 virtual_map[0];
+ u8 virtual_map[1];
} __attribute__ ((packed));

#define WLAN_SA_QUERY_TR_ID_LEN 16
@@ -1392,4 +1392,34 @@ static inline unsigned long ieee80211_tu
return 1024 * tu;
}

+/**
+ * ieee80211_check_tim - check if AID bit is set in TIM
+ * @tim: the TIM IE
+ * @tim_len: length of the TIM IE
+ * @aid: the AID to look for
+ */
+static inline bool ieee80211_check_tim(struct ieee80211_tim_ie *tim,
+ u8 tim_len, u16 aid)
+{
+ u8 mask;
+ u8 index, indexn1, indexn2;
+
+ if (unlikely(!tim || tim_len < sizeof(*tim)))
+ return false;
+
+ aid &= 0x3fff;
+ index = aid / 8;
+ mask = 1 << (aid & 7);
+
+ indexn1 = tim->bitmap_ctrl & 0xfe;
+ indexn2 = tim_len + indexn1 - 4;
+
+ if (index < indexn1 || index > indexn2)
+ return false;
+
+ index -= indexn1;
+
+ return !!(tim->virtual_map[index] & mask);
+}
+
#endif /* LINUX_IEEE80211_H */
--- wireless-testing.orig/net/mac80211/ieee80211_i.h 2009-04-16 23:56:05.000000000 +0200
+++ wireless-testing/net/mac80211/ieee80211_i.h 2009-04-16 23:56:06.000000000 +0200
@@ -844,7 +844,7 @@ struct ieee802_11_elems {
u8 *fh_params;
u8 *ds_params;
u8 *cf_params;
- u8 *tim;
+ struct ieee80211_tim_ie *tim;
u8 *ibss_params;
u8 *challenge;
u8 *wpa;
--- wireless-testing.orig/net/mac80211/util.c 2009-04-16 23:56:05.000000000 +0200
+++ wireless-testing/net/mac80211/util.c 2009-04-16 23:56:06.000000000 +0200
@@ -588,8 +588,10 @@ u32 ieee802_11_parse_elems_crc(u8 *start
elems->cf_params_len = elen;
break;
case WLAN_EID_TIM:
- elems->tim = pos;
- elems->tim_len = elen;
+ if (elen >= sizeof(struct ieee80211_tim_ie)) {
+ elems->tim = (void *)pos;
+ elems->tim_len = elen;
+ }
break;
case WLAN_EID_IBSS_PARAMS:
elems->ibss_params = pos;
--- wireless-testing.orig/net/mac80211/mlme.c 2009-04-16 23:56:05.000000000 +0200
+++ wireless-testing/net/mac80211/mlme.c 2009-04-17 00:07:53.000000000 +0200
@@ -677,27 +677,6 @@ static void ieee80211_sta_wmm_params(str
}
}

-static bool ieee80211_check_tim(struct ieee802_11_elems *elems, u16 aid)
-{
- u8 mask;
- u8 index, indexn1, indexn2;
- struct ieee80211_tim_ie *tim = (struct ieee80211_tim_ie *) elems->tim;
-
- aid &= 0x3fff;
- index = aid / 8;
- mask = 1 << (aid & 7);
-
- indexn1 = tim->bitmap_ctrl & 0xfe;
- indexn2 = elems->tim_len + indexn1 - 4;
-
- if (index < indexn1 || index > indexn2)
- return false;
-
- index -= indexn1;
-
- return !!(tim->virtual_map[index] & mask);
-}
-
static u32 ieee80211_handle_bss_capability(struct ieee80211_sub_if_data *sdata,
u16 capab, bool erp_valid, u8 erp)
{
@@ -1805,7 +1784,8 @@ static void ieee80211_rx_mgmt_beacon(str
care_about_ies, ncrc);

if (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK)
- directed_tim = ieee80211_check_tim(&elems, ifmgd->aid);
+ directed_tim = ieee80211_check_tim(elems.tim, elems.tim_len,
+ ifmgd->aid);

ncrc = crc32_be(ncrc, (void *)&directed_tim, sizeof(directed_tim));