rtnetlink: Use nlmsg_payload in valid_fdb_dump_strict

Leverage the new nlmsg_payload() helper to avoid checking for message
size and then reading the nlmsg data.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250414-nlmsg-v2-4-3d90cb42c6af@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 3852621..f5c0180 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -4887,12 +4887,12 @@ static int valid_fdb_dump_strict(const struct nlmsghdr *nlh,
        struct ndmsg *ndm;
        int err, i;
 
-       if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ndm))) {
+       ndm = nlmsg_payload(nlh, sizeof(*ndm));
+       if (!ndm) {
                NL_SET_ERR_MSG(extack, "Invalid header for fdb dump request");
                return -EINVAL;
        }
 
-       ndm = nlmsg_data(nlh);
        if (ndm->ndm_pad1  || ndm->ndm_pad2  || ndm->ndm_state ||
            ndm->ndm_flags || ndm->ndm_type) {
                NL_SET_ERR_MSG(extack, "Invalid values in header for fdb dump request");