Virtualization - Nov 2011 - [patch 1/2] xen-gntalloc: integer overflow in gntalloc_ioctl_alloc()

On 32 bit systems a high value of op.count could lead to an integer
overflow in the kzalloc() and gref_ids would be smaller than
expected.  If the you triggered another integer overflow in
"if (gref_size + op.count > limit)" then you'd probably get
memory
corruption inside add_grefs().

Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index f6832f4..23c60cf 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -280,7 +280,7 @@ static long gntalloc_ioctl_alloc(struct
gntalloc_file_private_data *priv,
 		goto out;
 	}
 
-	gref_ids = kzalloc(sizeof(gref_ids[0]) * op.count, GFP_TEMPORARY);
+	gref_ids = kcalloc(op.count, sizeof(gref_ids[0]), GFP_TEMPORARY);
 	if (!gref_ids) {
 		rc = -ENOMEM;
 		goto out;

On Fri, Nov 04, 2011 at 09:24:08PM +0300, Dan Carpenter
wrote:
> On 32 bit systems a high value of op.count could lead to an integer
> overflow in the kzalloc() and gref_ids would be smaller than
> expected.  If the you triggered another integer overflow in
> "if (gref_size + op.count > limit)" then you'd probably
get memory
> corruption inside add_grefs().
> 
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
Great! Keep them coming!  Will push for stable and 3.2.
> 
> diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
> index f6832f4..23c60cf 100644
> --- a/drivers/xen/gntalloc.c
> +++ b/drivers/xen/gntalloc.c
> @@ -280,7 +280,7 @@ static long gntalloc_ioctl_alloc(struct
gntalloc_file_private_data *priv,
>  		goto out;
>  	}
>  
> -	gref_ids = kzalloc(sizeof(gref_ids[0]) * op.count, GFP_TEMPORARY);
> +	gref_ids = kcalloc(op.count, sizeof(gref_ids[0]), GFP_TEMPORARY);
>  	if (!gref_ids) {
>  		rc = -ENOMEM;
>  		goto out;