From: Florian Westphal Date: Wed, 19 Jul 2023 22:29:58 +0000 (+0200) Subject: netfilter: nf_tables: fix spurious set element insertion failure X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=ddbd8be68941985f166f5107109a90ce13147c44;p=linux.git netfilter: nf_tables: fix spurious set element insertion failure On some platforms there is a padding hole in the nft_verdict structure, between the verdict code and the chain pointer. On element insertion, if the new element clashes with an existing one and NLM_F_EXCL flag isn't set, we want to ignore the -EEXIST error as long as the data associated with duplicated element is the same as the existing one. The data equality check uses memcmp. For normal data (NFT_DATA_VALUE) this works fine, but for NFT_DATA_VERDICT padding area leads to spurious failure even if the verdict data is the same. This then makes the insertion fail with 'already exists' error, even though the new "key : data" matches an existing entry and userspace told the kernel that it doesn't want to receive an error indication. Fixes: c016c7e45ddf ("netfilter: nf_tables: honor NLM_F_EXCL flag in set element insertion") Signed-off-by: Florian Westphal --- diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 237f739da3ca7..79c7eee33dcde 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -10517,6 +10517,9 @@ static int nft_verdict_init(const struct nft_ctx *ctx, struct nft_data *data, if (!tb[NFTA_VERDICT_CODE]) return -EINVAL; + + /* zero padding hole for memcmp */ + memset(data, 0, sizeof(*data)); data->verdict.code = ntohl(nla_get_be32(tb[NFTA_VERDICT_CODE])); switch (data->verdict.code) {