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netfilter: nft_compat: do not dump private area

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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>
This commit is contained in:
Pablo Neira Ayuso 2018-10-09 20:06:36 +02:00
parent 18c0ab8736
commit d701d81172
1 changed files with 22 additions and 2 deletions
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24
net/netfilter/nft_compat.c
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@ -290,6 +290,24 @@ nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
module_put(target->me); module_put(target->me);
} }
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) static int nft_target_dump(struct sk_buff *skb, const struct nft_expr *expr)
{ {
const struct xt_target *target = expr->ops->data; const struct xt_target *target = expr->ops->data;
@ -297,7 +315,8 @@ static int nft_target_dump(struct sk_buff *skb, const struct nft_expr *expr)
if (nla_put_string(skb, NFTA_TARGET_NAME, target->name) || if (nla_put_string(skb, NFTA_TARGET_NAME, target->name) ||
nla_put_be32(skb, NFTA_TARGET_REV, htonl(target->revision)) || 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; goto nla_put_failure;
return 0; return 0;
@ -532,7 +551,8 @@ static int __nft_match_dump(struct sk_buff *skb, const struct nft_expr *expr,
if (nla_put_string(skb, NFTA_MATCH_NAME, match->name) || if (nla_put_string(skb, NFTA_MATCH_NAME, match->name) ||
nla_put_be32(skb, NFTA_MATCH_REV, htonl(match->revision)) || 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; goto nla_put_failure;
return 0; return 0;