Re: [patch] s390: potential buffer overflow

[ebiederm@xmission.com (Eric W. Biederman)]

Dan Carpenter <error27@gmail.com> writes:

> "len" hasn't been properly range checked so we shouldn't use it as an
> array offset.  This can only be written to by root but it would still be
> annoying to accidentally write more than 3 characters and corrupt your
> memory.
>
> Signed-off-by: Dan Carpenter <error27@gmail.com>
> ---
> I don't have a cross compile environment to compile this.  Sorry.  :/
>
> diff --git a/drivers/s390/char/sclp_async.c b/drivers/s390/char/sclp_async.c
> index f449c69..72c2e90 100644
> --- a/drivers/s390/char/sclp_async.c
> +++ b/drivers/s390/char/sclp_async.c
> @@ -84,7 +84,7 @@ static int proc_handler_callhome(struct ctl_table *ctl, int write,
>  		rc = copy_from_user(buf, buffer, sizeof(buf));
>  		if (rc != 0)
>  			return -EFAULT;
> -		buf[len - 1] = '\0';
> +		buf[sizeof(buf) - 1] = '\0';
>  		if (strict_strtoul(buf, 0, &val) != 0)
>  			return -EINVAL;
>  		if (val != 0 && val != 1)
> @@ -99,6 +99,7 @@ static int proc_handler_callhome(struct ctl_table *ctl, int write,
>  static struct ctl_table callhome_table[] = {
>  	{
>  		.procname	= "callhome",
> +		.maxlen		= 3,
>  		.mode		= 0644,
>  		.proc_handler	= proc_handler_callhome,
>  	},

Setting maxlen won't do any good as proc_handler_callhome doesn't look at it.

Eric