Commit 8c2d45b2 authored Mar 22, 2020 by Pablo Neira Ayuso

netfilter: nf_tables: Allow set back-ends to report partial overlaps on insertion

Currently, the -EEXIST return code of ->insert() callbacks is ambiguous: it
might indicate that a given element (including intervals) already exists as
such, or that the new element would clash with existing ones.

If identical elements already exist, the front-end is ignoring this without
returning error, in case NLM_F_EXCL is not set. However, if the new element
can't be inserted due an overlap, we should report this to the user.

To this purpose, allow set back-ends to return -ENOTEMPTY on collision with
existing elements, translate that to -EEXIST, and return that to userspace,
no matter if NLM_F_EXCL was set.

Reported-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent 749f6f68

net/netfilter/nf_tables_api.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -5082,6 +5082,11 @@ static int nft_add_set_elem(struct nft_ctx ctx, struct nft_set set,
		err = -EBUSY;
		else if (!(nlmsg_flags & NLM_F_EXCL))
		err = 0;
		} else if (err == -ENOTEMPTY) {
		/* ENOTEMPTY reports overlapping between this element
		* and an existing one.
		*/
		err = -EEXIST;
		}
		goto err_element_clash;
		}

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