nl80211: Define policy for packet pattern attributes

Define a policy for packet pattern attributes in order to fix a
potential read over the end of the buffer during nla_get_u32()
of the NL80211_WOWLAN_PKTPAT_OFFSET attribute.

Note that the data there can always be read due to SKB allocation
(with alignment and struct skb_shared_info at the end), but the
data might be uninitialized. This could be used to leak some data
from uninitialized vmalloc() memory, but most drivers don't allow
an offset (so you'd just get -EINVAL if the data is non-zero) or
just allow it with a fixed value - 100 or 128 bytes, so anything
above that would get -EINVAL. With brcmfmac the limit is 1500 so
(at least) one byte could be obtained.

Cc: stable@kernel.org
Bug: 64403015
Signed-off-by: Peng Xu <pxu@qti.qualcomm.com>
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
[rewrite description based on SKB allocation knowledge]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Change-Id: I6d8975ba163808481637a21fd6e57f917ec10ed4
Git-commit: ad670233c9e1d5feb365d870e30083ef1b889177
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git


CRs-fixed: 2116387
[Backport: Fix conflicts]
Signed-off-by: Vidyullatha Kanchanapally <vidyullatha@codeaurora.org>
Signed-off-by: Peng Xu <pxu@codeaurora.org>
Signed-off-by: Srinivas Dasari <dasaris@codeaurora.org>