mac80211: verify that skb data is present

A number of places in the mesh code don't check that
the frame data is present and in the skb header when
trying to access. Add those checks and the necessary
pskb_may_pull() calls. This prevents accessing data
that doesn't actually exist.

To do this, export ieee80211_get_mesh_hdrlen() to be
able to use it in mac80211.

Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index f8cd4cf3fad8..7d5b6000378b 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2652,6 +2652,15 @@ unsigned int ieee80211_get_hdrlen_from_skb(const struct sk_buff *skb);
 unsigned int __attribute_const__ ieee80211_hdrlen(__le16 fc);
 
 /**
+ * ieee80211_get_mesh_hdrlen - get mesh extension header length
+ * @meshhdr: the mesh extension header, only the flags field
+ *      (first byte) will be accessed
+ * Returns the length of the extension header, which is always at
+ * least 6 bytes and at most 18 if address 5 and 6 are present.
+ */
+unsigned int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr);
+
+/**
  * DOC: Data path helpers
  *
  * In addition to generic utilities, cfg80211 also offers