xtables: extend matches and targets with .usersize

In matches and targets that define a kernel-only tail to their
xt_match and xt_target data structs, add a field .usersize that
specifies up to where data is to be shared with userspace.

Performed a search for comment "Used internally by the kernel" to find
relevant matches and targets. Manually inspected the structs to derive
a valid offsetof.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/netfilter/xt_string.c b/net/netfilter/xt_string.c
index 0bc3460319c8..423293ee57c2 100644
--- a/net/netfilter/xt_string.c
+++ b/net/netfilter/xt_string.c
@@ -77,6 +77,7 @@ static struct xt_match xt_string_mt_reg __read_mostly = {
 	.match      = string_mt,
 	.destroy    = string_mt_destroy,
 	.matchsize  = sizeof(struct xt_string_info),
+	.usersize   = offsetof(struct xt_string_info, config),
 	.me         = THIS_MODULE,
 };