netfilter: nfnetlink_acct: validate NFACCT_FILTER parameters

BugLink: https://bugs.launchpad.net/bugs/1822271

commit 017b1b6d upstream.

nfacct_filter_alloc doesn't validate the NFACCT_FILTER_MASK and
NFACCT_FILTER_VALUE parameters which can trigger a NULL pointer
dereference. CAP_NET_ADMIN is required to trigger the bug.
Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/netfilter/nfnetlink_acct.c

@@ -243,6 +243,9 @@ nfacct_filter_alloc(const struct nlattr * const attr)
 	if (err < 0)
 		return ERR_PTR(err);
 
+	if (!tb[NFACCT_FILTER_MASK] || !tb[NFACCT_FILTER_VALUE])
+		return ERR_PTR(-EINVAL);
+
 	filter = kzalloc(sizeof(struct nfacct_filter), GFP_KERNEL);
 	if (!filter)
 		return ERR_PTR(-ENOMEM);