Subject: Re: [PATCH] ipvs: Add boundary check on ioctl arguments

From: Arjan van de Ven <[email-masked]>
Date: Wed, 30 Sep 2009 17:18:33 +0200

On Wed, 30 Sep 2009 15:38:12 +0200
Hannes Eder <[email-masked]> wrote:
>  > @@ -2353,17 +2357,25 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd,
>  > void __user 
> *user, int *len)
>  >  {
>  >  	unsigned char arg[128];
> 
> can MAX_ARG_LEN be used here?

I am not convinced... it is a different numerical value,
so it could be an ABI change. Rather not do that in this
type of patch...

>  > +	copylen = get_arglen[GET_CMDID(cmd)];
>  > +	if (copylen > 128)
> 
> I think it's better to use 'copylen > sizeof(arg)' here.

fair enough; updated patch below

>>From 28ae217858e683c0c94c02219d46a9a9c87f61c6 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <[email-masked]>
Date: Wed, 30 Sep 2009 13:05:51 +0200
Subject: [PATCH] ipvs: Add boundary check on ioctl arguments

The ipvs code has a nifty system for doing the size of ioctl command copies;
it defines an array with values into which it indexes the cmd to find the
right length.

Unfortunately, the ipvs code forgot to check if the cmd was in the range
that the array provides, allowing for an index outside of the array,
which then gives a "garbage" result into the length, which then gets
used for copying into a stack buffer.

Fix this by adding sanity checks on these as well as the copy size.

Signed-off-by: Arjan van de Ven <[email-masked]>
---
 net/netfilter/ipvs/ip_vs_ctl.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index ac624e5..7adc876 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2077,6 +2077,10 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
 
+	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_SET_MAX + 1)
+		return -EINVAL;
+	if (len < 0 || len >  sizeof(arg))
+		return -EINVAL;
 	if (len != set_arglen[SET_CMDID(cmd)]) {
 		pr_err("set_ctl: len %u != %u\n",
 		       len, set_arglen[SET_CMDID(cmd)]);
@@ -2353,17 +2357,25 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
 {
 	unsigned char arg[128];
 	int ret = 0;
+	unsigned int copylen;
 
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
 
+	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_GET_MAX + 1)
+		return -EINVAL;
+
 	if (*len < get_arglen[GET_CMDID(cmd)]) {
 		pr_err("get_ctl: len %u < %u\n",
 		       *len, get_arglen[GET_CMDID(cmd)]);
 		return -EINVAL;
 	}
 
-	if (copy_from_user(arg, user, get_arglen[GET_CMDID(cmd)]) != 0)
+	copylen = get_arglen[GET_CMDID(cmd)];
+	if (copylen > sizeof(arg))
+		return -EINVAL;
+
+	if (copy_from_user(arg, user, copylen) != 0)
 		return -EFAULT;
 
 	if (mutex_lock_interruptible(&__ip_vs_mutex))
-- 
1.6.2.5

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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