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net, neigh: Reject creating NUD_PERMANENT with NTF_MANAGED entries

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The combination of NUD_PERMANENT + NTF_MANAGED is not supported and does
not make sense either given the former indicates a static/fixed neighbor
entry whereas the latter a dynamically resolved one. While it is possible
to transition from one over to the other, we should however reject such
creation attempts.

Fixes: 7482e3841d52 ("net, neigh: Add NTF_MANAGED flag for managed neighbor entries")
Suggested-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Daniel Borkmann 2021-10-13 15:21:40 +02:00 committed by Jakub Kicinski
parent c8e80c1169
commit 30fc7efa38
1 changed files with 8 additions and 3 deletions
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11
net/core/neighbour.c
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@ -1999,15 +1999,20 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
neigh = neigh_lookup(tbl, dst, dev);
if (neigh == NULL) {
bool exempt_from_gc;
bool ndm_permanent = ndm->ndm_state & NUD_PERMANENT;
bool exempt_from_gc = ndm_permanent ||
ndm_flags & NTF_EXT_LEARNED;
if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
err = -ENOENT;
goto out;
}
if (ndm_permanent && (ndm_flags & NTF_MANAGED)) {
NL_SET_ERR_MSG(extack, "Invalid NTF_* flag for permanent entry");
err = -EINVAL;
goto out;
}
exempt_from_gc = ndm->ndm_state & NUD_PERMANENT ||
ndm_flags & NTF_EXT_LEARNED;
neigh = ___neigh_create(tbl, dst, dev,
ndm_flags &
(NTF_EXT_LEARNED | NTF_MANAGED),