[PATCH AUTOSEL 5.4 24/32] netfilter: nf_tables: Allow set back-ends to report partial overlaps on insertion

Sasha Levin
2020-04-07T00:05:45Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 8c2d45b2b65ca1f215244be1c600236e83f9815f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_tables_api.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 068daff41f6e6..ddaaf5e535d58 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4689,6 +4689,11 @@ 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 err5;
}
--
2.20.1