linux-kernel - [PATCH] netfilter: fix pointer leaks to userspace

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Date:   Mon, 29 Jan 2018 13:21:20 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     pablo@...filter.org, kadlec@...ckhole.kfki.hu, fw@...len.de,
        davem@...emloft.net
Cc:     andreyknvl@...gle.com, Dmitry Vyukov <dvyukov@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] netfilter: fix pointer leaks to userspace

Several netfilter matches and targets put kernel pointers into
info objects, but don't set usersize in descriptors.
This leads to kernel pointer leaks if a match/target is set
and then read back to userspace.

Properly set usersize for these matches/targets.

Found with manual code inspection.

Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc: Florian Westphal <fw@...len.de>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Kees Cook <keescook@...omium.org>
Cc: netfilter-devel@...r.kernel.org
Cc: coreteam@...filter.org
Cc: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 net/netfilter/xt_IDLETIMER.c | 1 +
 net/netfilter/xt_LED.c       | 1 +
 net/netfilter/xt_limit.c     | 3 +--
 net/netfilter/xt_nfacct.c    | 1 +
 net/netfilter/xt_statistic.c | 1 +
 5 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/xt_IDLETIMER.c b/net/netfilter/xt_IDLETIMER.c
index ee3421ad108d..6c2482b709b1 100644
--- a/net/netfilter/xt_IDLETIMER.c
+++ b/net/netfilter/xt_IDLETIMER.c
@@ -252,6 +252,7 @@ static struct xt_target idletimer_tg __read_mostly = {
 	.family		= NFPROTO_UNSPEC,
 	.target		= idletimer_tg_target,
 	.targetsize     = sizeof(struct idletimer_tg_info),
+	.usersize	= offsetof(struct idletimer_tg_info, timer),
 	.checkentry	= idletimer_tg_checkentry,
 	.destroy        = idletimer_tg_destroy,
 	.me		= THIS_MODULE,
diff --git a/net/netfilter/xt_LED.c b/net/netfilter/xt_LED.c
index 0971634e5444..1dcad893df78 100644
--- a/net/netfilter/xt_LED.c
+++ b/net/netfilter/xt_LED.c
@@ -198,6 +198,7 @@ static struct xt_target led_tg_reg __read_mostly = {
 	.family		= NFPROTO_UNSPEC,
 	.target		= led_tg,
 	.targetsize	= sizeof(struct xt_led_info),
+	.usersize	= offsetof(struct xt_led_info, internal_data),
 	.checkentry	= led_tg_check,
 	.destroy	= led_tg_destroy,
 	.me		= THIS_MODULE,
diff --git a/net/netfilter/xt_limit.c b/net/netfilter/xt_limit.c
index d27b5f1ea619..61403b77361c 100644
--- a/net/netfilter/xt_limit.c
+++ b/net/netfilter/xt_limit.c
@@ -193,9 +193,8 @@ static struct xt_match limit_mt_reg __read_mostly = {
 	.compatsize       = sizeof(struct compat_xt_rateinfo),
 	.compat_from_user = limit_mt_compat_from_user,
 	.compat_to_user   = limit_mt_compat_to_user,
-#else
-	.usersize         = offsetof(struct xt_rateinfo, prev),
 #endif
+	.usersize         = offsetof(struct xt_rateinfo, prev),
 	.me               = THIS_MODULE,
 };
 
diff --git a/net/netfilter/xt_nfacct.c b/net/netfilter/xt_nfacct.c
index cc0518fe598e..6f92d25590a8 100644
--- a/net/netfilter/xt_nfacct.c
+++ b/net/netfilter/xt_nfacct.c
@@ -62,6 +62,7 @@ static struct xt_match nfacct_mt_reg __read_mostly = {
 	.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,
 };
 
diff --git a/net/netfilter/xt_statistic.c b/net/netfilter/xt_statistic.c
index 11de55e7a868..8710fdba2ae2 100644
--- a/net/netfilter/xt_statistic.c
+++ b/net/netfilter/xt_statistic.c
@@ -84,6 +84,7 @@ static struct xt_match xt_statistic_mt_reg __read_mostly = {
 	.checkentry = statistic_mt_check,
 	.destroy    = statistic_mt_destroy,
 	.matchsize  = sizeof(struct xt_statistic_info),
+	.usersize   = offsetof(struct xt_statistic_info, master),
 	.me         = THIS_MODULE,
 };
 
-- 
2.16.0.rc1.238.g530d649a79-goog