[PATCH] sysctl: fix binary sysctl overflow

[PATCH] sysctl: fix binary sysctl overflow

[Lucian Adrian Grijincu]

We allocated a vector of CTL_MAXNAME elements and considered
[0, CTL_MAXNAME] as valid indexes in the vector.

This fixes valid index range to be [0, CTL_MAXNAME).

I guess this should be backported to stable trees too.

Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
---
 kernel/sysctl_binary.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index b875bed..e2f377c 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -1446,7 +1446,7 @@ static ssize_t do_sysctl(int __user *args_name, int nlen,
 	int i;
 
 	/* Check args->nlen. */
-	if (nlen < 0 || nlen > CTL_MAXNAME)
+	if (nlen < 0 || nlen >= CTL_MAXNAME)
 		return -ENOTDIR;
 	/* Read in the sysctl name for simplicity */
 	for (i = 0; i < nlen; i++)
-- 
1.7.4.rc1.7.g2cf08.dirty

Re: [PATCH] sysctl: fix binary sysctl overflow

[Eric W. Biederman]

Lucian Adrian Grijincu <lucian.grijincu@gmail.com> writes:

> We allocated a vector of CTL_MAXNAME elements and considered
> [0, CTL_MAXNAME] as valid indexes in the vector.
>
> This fixes valid index range to be [0, CTL_MAXNAME).
>
> I guess this should be backported to stable trees too.

No.  This part of the code is correct.  0 is a valid index,
and the array is only CTL_MAXNAME entries long.

I think the maximum depth of this table is only about 6, but
feel free to count and tell me CTL_MAXNAME is set too low.

Eric


>
> Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
> ---
>  kernel/sysctl_binary.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
> index b875bed..e2f377c 100644
> --- a/kernel/sysctl_binary.c
> +++ b/kernel/sysctl_binary.c
> @@ -1446,7 +1446,7 @@ static ssize_t do_sysctl(int __user *args_name, int nlen,
>  	int i;
>  
>  	/* Check args->nlen. */
> -	if (nlen < 0 || nlen > CTL_MAXNAME)
> +	if (nlen < 0 || nlen >= CTL_MAXNAME)
>  		return -ENOTDIR;
>  	/* Read in the sysctl name for simplicity */
>  	for (i = 0; i < nlen; i++)

Re: [PATCH] sysctl: fix binary sysctl overflow

[Lucian Adrian Grijincu]

On Fri, Feb 4, 2011 at 11:09 PM, Eric W. Biederman
<ebiederm@xmission.com> wrote:
> I think the maximum depth of this table is only about 6, but
> feel free to count and tell me CTL_MAXNAME is set too low.


Oh, you are right, after reading the code a bit more attentive I see
that the check was right from the start :)

Kids, don't drink and submit kernel patches :P

-- 
 .
..: Lucian