Re: [patch] mtd: sm_ftl: heap corruption in sm_create_sysfs_attributes()

[walter harms <wharms@bfs.de>]

Am 05.12.2013 12:02, schrieb Dan Carpenter:
> We always put a NUL terminator one space past the end of the "vendor"
> buffer.  Also I think the strnlen() limiter is off by one so I have made
> it smaller.
> 
> Fixes: 7d17c02a01a1 ('mtd: Add new SmartMedia/xD FTL')
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> Static analysis stuff.  Untested.
> 
> diff --git a/drivers/mtd/sm_ftl.c b/drivers/mtd/sm_ftl.c
> index 4b8e89583f2a..7c452714df8d 100644
> --- a/drivers/mtd/sm_ftl.c
> +++ b/drivers/mtd/sm_ftl.c
> @@ -59,11 +59,12 @@ static struct attribute_group *sm_create_sysfs_attributes(struct sm_ftl *ftl)
>  	struct attribute_group *attr_group;
>  	struct attribute **attributes;
>  	struct sm_sysfs_attribute *vendor_attribute;
> +	int vendor_len;
> +	char *vendor;
>  
> -	int vendor_len = strnlen(ftl->cis_buffer + SM_CIS_VENDOR_OFFSET,
> -					SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET);
> -
> -	char *vendor = kmalloc(vendor_len, GFP_KERNEL);
> +	vendor_len = strnlen(ftl->cis_buffer + SM_CIS_VENDOR_OFFSET,
> +			     SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET - 1);
> +	vendor = kmalloc(vendor_len + 1, GFP_KERNEL);
>  	if (!vendor)
>  		goto error1;
>  	memcpy(vendor, ftl->cis_buffer + SM_CIS_VENDOR_OFFSET, vendor_len);

Hi Dan,
is this a case for kstr(n)dup() ? like:

int maxlen=SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET-1;
char *buf=ftl->cis_buffer + SM_CIS_VENDOR_OFFSET;
vendor=kstrndup(buf,maxlen,GFP_KERNEL);
if (!vendor)
	goto error1;

i added maxlen, buf to to help me understand the code,
when the source is save kstrdup() is also an option

just my to cents,
 wh