On 10/13/21 7:21 AM, Daniel Borkmann wrote:
> Instead of open-coding a check for invalid bits in NTF_EXT_MASK, we can just
> use the NLA_POLICY_MASK() helper instead, and simplify NDA_FLAGS_EXT sanity
> check this way.
>
> Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> ---
> net/core/neighbour.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 4fc601f9cd06..922b9ed0fe76 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -1834,7 +1834,7 @@ const struct nla_policy nda_policy[NDA_MAX+1] = {
> [NDA_MASTER] = { .type = NLA_U32 },
> [NDA_PROTOCOL] = { .type = NLA_U8 },
> [NDA_NH_ID] = { .type = NLA_U32 },
> - [NDA_FLAGS_EXT] = { .type = NLA_U32 },
> + [NDA_FLAGS_EXT] = NLA_POLICY_MASK(NLA_U32, NTF_EXT_MASK),
> [NDA_FDB_EXT_ATTRS] = { .type = NLA_NESTED },
> };
>
> @@ -1936,10 +1936,6 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
> if (tb[NDA_FLAGS_EXT]) {
> u32 ext = nla_get_u32(tb[NDA_FLAGS_EXT]);
>
> - if (ext & ~NTF_EXT_MASK) {
> - NL_SET_ERR_MSG(extack, "Invalid extended flags");
> - goto out;
> - }
> BUILD_BUG_ON(sizeof(neigh->flags) * BITS_PER_BYTE <
> (sizeof(ndm->ndm_flags) * BITS_PER_BYTE +
> hweight32(NTF_EXT_MASK)));
>
I get that NLA_POLICY_MASK wants to standardize the logic, but the
generic extack message "reserved bit set" is less useful than the one here.
