cfg80211: Validate frequencies nested in NL80211_ATTR_SCAN_FREQUENCIES

validate_scan_freqs() retrieves frequencies from attributes
nested in the attribute NL80211_ATTR_SCAN_FREQUENCIES with
nla_get_u32(), which reads 4 bytes from each attribute
without validating the size of data received. Attributes
nested in NL80211_ATTR_SCAN_FREQUENCIES don't have an nla policy.

Validate size of each attribute before parsing to avoid potential buffer
overread.

Fixes: 2a519311 ("cfg80211/nl80211: scanning (and mac80211 update to use it)")
Cc: stable@vger.kernel.org
Signed-off-by: Srinivas Dasari <dasaris@qti.qualcomm.com>
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211.git


Git-commit: d7f13f7450369281a5d0ea463cc69890a15923ae
Change-Id: I34198e599a950c30495ec3445799972db7f9f42e
CRs-Fixed: 2069828
Signed-off-by: Srinivas Dasari <dasaris@codeaurora.org>