2011-02-04 20:39:09

by Lucian Adrian Grijincu

Subject: [PATCH] sysctl: fix binary sysctl overflow

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 <[email protected]>
---
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

2011-02-04 21:09:44

by Eric W. Biederman

Subject: Re: [PATCH] sysctl: fix binary sysctl overflow

Lucian Adrian Grijincu <[email protected]> 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 <[email protected]>
> ---
> 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++)

2011-02-04 21:33:12

by Lucian Adrian Grijincu

Subject: Re: [PATCH] sysctl: fix binary sysctl overflow

On Fri, Feb 4, 2011 at 11:09 PM, Eric W. Biederman
<[email protected]> 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