Re: [ 010/122] smack: off by one error

From: Casey Schaufler
Date: Tue Aug 07 2012 - 20:11:27 EST


On 8/7/2012 3:24 PM, Greg Kroah-Hartman wrote:
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> 3.5-stable review patch. If anyone has any objections, please let me know.

No objection here.

>
> ------------------
>
> From: Alan Cox <alan@xxxxxxxxxxxxxxx>
>
> commit 3b9fc37280c521b086943f9aedda767f5bf3b2d3 upstream.
>
> Consider the input case of a rule that consists entirely of non space
> symbols followed by a \0. Say 64 + \0
>
> In this case strlen(data) = 64
> kzalloc of subject and object are 64 byte objects
> sscanfdata, "%s %s %s", subject, ...)
>
> will put 65 bytes into subject.
>
> Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
> Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> ---
> security/smack/smackfs.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -325,11 +325,11 @@ static int smk_parse_long_rule(const cha
> int datalen;
> int rc = -1;
>
> - /*
> - * This is probably inefficient, but safe.
> - */
> + /* This is inefficient */
> datalen = strlen(data);
> - subject = kzalloc(datalen, GFP_KERNEL);
> +
> + /* Our first element can be 64 + \0 with no spaces */
> + subject = kzalloc(datalen + 1, GFP_KERNEL);
> if (subject == NULL)
> return -1;
> object = kzalloc(datalen, GFP_KERNEL);
>
>
> --
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