[PATCH AUTOSEL 4.19 195/209] netfilter: nft_compat: do not dump private area

Sasha Levin
2019-11-13T01:56:07Z

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

[ Upstream commit d701d8117200399d85e63a737d2e4e897932f3b6 ]

Zero pad private area, otherwise we expose private kernel pointer to
userspace. This patch also zeroes the tail area after the ->matchsize
and ->targetsize that results from XT_ALIGN().

Fixes: 0ca743a55991 ("netfilter: nf_tables: add compatibility layer for x_tables")
Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nft_compat.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index 1245e02239d90..469f9da5073bf 100644
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -269,6 +269,24 @@ nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
kfree(expr->ops);
}

+static int nft_extension_dump_info(struct sk_buff *skb, int attr,
+ const void *info,
+ unsigned int size, unsigned int user_size)
+{
+ unsigned int info_size, aligned_size = XT_ALIGN(size);
+ struct nlattr *nla;
+
+ nla = nla_reserve(skb, attr, aligned_size);
+ if (!nla)
+ return -1;
+
+ info_size = user_size ? : size;
+ memcpy(nla_data(nla), info, info_size);
+ memset(nla_data(nla) + info_size, 0, aligned_size - info_size);
+
+ return 0;
+}
+
static int nft_target_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
const struct xt_target *target = expr->ops->data;
@@ -276,7 +294,8 @@ static int nft_target_dump(struct sk_buff *skb, const struct nft_expr *expr)

if (nla_put_string(skb, NFTA_TARGET_NAME, target->name) ||
nla_put_be32(skb, NFTA_TARGET_REV, htonl(target->revision)) ||
- nla_put(skb, NFTA_TARGET_INFO, XT_ALIGN(target->targetsize), info))
+ nft_extension_dump_info(skb, NFTA_TARGET_INFO, info,
+ target->targetsize, target->usersize))
goto nla_put_failure;

return 0;
@@ -504,7 +523,8 @@ static int __nft_match_dump(struct sk_buff *skb, const struct nft_expr *expr,

if (nla_put_string(skb, NFTA_MATCH_NAME, match->name) ||
nla_put_be32(skb, NFTA_MATCH_REV, htonl(match->revision)) ||
- nla_put(skb, NFTA_MATCH_INFO, XT_ALIGN(match->matchsize), info))
+ nft_extension_dump_info(skb, NFTA_MATCH_INFO, info,
+ match->matchsize, match->usersize))
goto nla_put_failure;

return 0;
--
2.20.1