2018-01-29 12:22:15

by Dmitry Vyukov

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 <[email protected]>
Cc: Pablo Neira Ayuso <[email protected]>
Cc: Jozsef Kadlecsik <[email protected]>
Cc: Florian Westphal <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
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

2018-01-31 13:59:55

by Pablo Neira Ayuso

Subject: Re: [PATCH] netfilter: fix pointer leaks to userspace

On Mon, Jan 29, 2018 at 01:21:20PM +0100, Dmitry Vyukov wrote:
> 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.

Applied, thanks!

I think this fixes:

ec2318904965 xtables: extend matches and targets with .usersize

So I'm going to add the Fixes: tag here, no problem.