[PATCH AUTOSEL 5.2 24/94] netfilter: xt_nfacct: Fix alignment mismatch in xt_nfacct_match_info

Sasha Levin
2019-09-04T16:19:53Z

From: Juliana Rodrigueiro <juliana.rodrigueiro@intra2net.com>

[ Upstream commit 89a26cd4b501e9511d3cd3d22327fc76a75a38b3 ]

When running a 64-bit kernel with a 32-bit iptables binary, the size of
the xt_nfacct_match_info struct diverges.

kernel: sizeof(struct xt_nfacct_match_info) : 40
iptables: sizeof(struct xt_nfacct_match_info)) : 36

Trying to append nfacct related rules results in an unhelpful message.
Although it is suggested to look for more information in dmesg, nothing
can be found there.

# iptables -A <chain> -m nfacct --nfacct-name <acct-object>
iptables: Invalid argument. Run `dmesg' for more information.

This patch fixes the memory misalignment by enforcing 8-byte alignment
within the struct's first revision. This solution is often used in many
other uapi netfilter headers.

Signed-off-by: Juliana Rodrigueiro <juliana.rodrigueiro@intra2net.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/uapi/linux/netfilter/xt_nfacct.h | 5 ++++
net/netfilter/xt_nfacct.c | 36 ++++++++++++++++--------
2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/include/uapi/linux/netfilter/xt_nfacct.h b/include/uapi/linux/netfilter/xt_nfacct.h
index 5c8a4d760ee34..b5123ab8d54a8 100644
--- a/include/uapi/linux/netfilter/xt_nfacct.h
+++ b/include/uapi/linux/netfilter/xt_nfacct.h
@@ -11,4 +11,9 @@ struct xt_nfacct_match_info {
struct nf_acct *nfacct;
};

+struct xt_nfacct_match_info_v1 {
+ char name[NFACCT_NAME_MAX];
+ struct nf_acct *nfacct __attribute__((aligned(8)));
+};
+
#endif /* _XT_NFACCT_MATCH_H */
diff --git a/net/netfilter/xt_nfacct.c b/net/netfilter/xt_nfacct.c
index d0ab1adf5bff8..5aab6df74e0f2 100644
--- a/net/netfilter/xt_nfacct.c
+++ b/net/netfilter/xt_nfacct.c
@@ -54,25 +54,39 @@ nfacct_mt_destroy(const struct xt_mtdtor_param *par)
nfnl_acct_put(info->nfacct);
}

-static struct xt_match nfacct_mt_reg __read_mostly = {
- .name = "nfacct",
- .family = NFPROTO_UNSPEC,
- .checkentry = nfacct_mt_checkentry,
- .match = nfacct_mt,
- .destroy = nfacct_mt_destroy,
- .matchsize = sizeof(struct xt_nfacct_match_info),
- .usersize = offsetof(struct xt_nfacct_match_info, nfacct),
- .me = THIS_MODULE,
+static struct xt_match nfacct_mt_reg[] __read_mostly = {
+ {
+ .name = "nfacct",
+ .revision = 0,
+ .family = NFPROTO_UNSPEC,
+ .checkentry = nfacct_mt_checkentry,
+ .match = nfacct_mt,
+ .destroy = nfacct_mt_destroy,
+ .matchsize = sizeof(struct xt_nfacct_match_info),
+ .usersize = offsetof(struct xt_nfacct_match_info, nfacct),
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "nfacct",
+ .revision = 1,
+ .family = NFPROTO_UNSPEC,
+ .checkentry = nfacct_mt_checkentry,
+ .match = nfacct_mt,
+ .destroy = nfacct_mt_destroy,
+ .matchsize = sizeof(struct xt_nfacct_match_info_v1),
+ .usersize = offsetof(struct xt_nfacct_match_info_v1, nfacct),
+ .me = THIS_MODULE,
+ },
};

static int __init nfacct_mt_init(void)
{
- return xt_register_match(&nfacct_mt_reg);
+ return xt_register_matches(nfacct_mt_reg, ARRAY_SIZE(nfacct_mt_reg));
}

static void __exit nfacct_mt_exit(void)
{
- xt_unregister_match(&nfacct_mt_reg);
+ xt_unregister_matches(nfacct_mt_reg, ARRAY_SIZE(nfacct_mt_reg));
}

module_init(nfacct_mt_init);
--
2.20.1