[PATCH 6.18 259/641] netfilter: nft_compat: add more restrictions on netlink attributes

Greg Kroah-Hartman
2026-02-25T01:46:48Z

6.18-stable review patch. If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

[ Upstream commit cda26c645946b08f070f20c166d4736767e4a805 ]

As far as I can see nothing bad can happen when NFTA_TARGET/MATCH_NAME
are too large because this calls x_tables helpers which check for the
length, but it seems better to already reject it during netlink parsing.

Rest of the changes avoid silent u8/u16 truncations.

For _TYPE, its expected to be only 1 or 0. In x_tables world, this
variable is set by kernel, for IPT_SO_GET_REVISION_TARGET its 1, for
all others its set to 0.

As older versions of nf_tables permitted any value except 1 to mean 'match',
keep this as-is but sanitize the value for consistency.

Fixes: 0ca743a55991 ("netfilter: nf_tables: add compatibility layer for x_tables")
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nft_compat.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index 72711d62fddfa..08f620311b03f 100644
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -134,7 +134,8 @@ static void nft_target_eval_bridge(const struct nft_expr *expr,
}

static const struct nla_policy nft_target_policy[NFTA_TARGET_MAX + 1] = {
- [NFTA_TARGET_NAME] = { .type = NLA_NUL_STRING },
+ [NFTA_TARGET_NAME] = { .type = NLA_NUL_STRING,
+ .len = XT_EXTENSION_MAXNAMELEN, },
[NFTA_TARGET_REV] = NLA_POLICY_MAX(NLA_BE32, 255),
[NFTA_TARGET_INFO] = { .type = NLA_BINARY },
};
@@ -434,7 +435,8 @@ static void nft_match_eval(const struct nft_expr *expr,
}

static const struct nla_policy nft_match_policy[NFTA_MATCH_MAX + 1] = {
- [NFTA_MATCH_NAME] = { .type = NLA_NUL_STRING },
+ [NFTA_MATCH_NAME] = { .type = NLA_NUL_STRING,
+ .len = XT_EXTENSION_MAXNAMELEN },
[NFTA_MATCH_REV] = NLA_POLICY_MAX(NLA_BE32, 255),
[NFTA_MATCH_INFO] = { .type = NLA_BINARY },
};
@@ -693,7 +695,12 @@ static int nfnl_compat_get_rcu(struct sk_buff *skb,

name = nla_data(tb[NFTA_COMPAT_NAME]);
rev = ntohl(nla_get_be32(tb[NFTA_COMPAT_REV]));
- target = ntohl(nla_get_be32(tb[NFTA_COMPAT_TYPE]));
+ /* x_tables api checks for 'target == 1' to mean target,
+ * everything else means 'match'.
+ * In x_tables world, the number is set by kernel, not
+ * userspace.
+ */
+ target = nla_get_be32(tb[NFTA_COMPAT_TYPE]) == htonl(1);

switch(family) {
case AF_INET:
--
2.51.0