cfg80211: Validate frequencies nested in NL80211_ATTR_SCAN_FREQUENCIES

cfg80211: Validate frequencies nested in NL80211_ATTR_SCAN_FREQUENCIES

BugLink: http://bugs.launchpad.net/bugs/1705707
commit d7f13f7450369281a5d0ea463cc69890a15923ae upstream.

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: 2a519311926 ("cfg80211/nl80211: scanning (and mac80211 update to use it)")
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>