[PATCH] rbd: fix double free on rbd_dev->header_name

[PATCH] rbd: fix double free on rbd_dev->header_name

[Ilya Dryomov]

If rbd_dev_image_probe() in rbd_dev_probe_parent() fails, header_name
is freed twice: once in rbd_dev_probe_parent() and then in its caller
rbd_dev_image_probe() (rbd_dev_image_probe() is called recursively to
handle parent images).

rbd_dev_probe_parent() is responsible for probing the parent, so it
shoudn't mock with clone's fields.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 drivers/block/rbd.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index bc67a93aa4f4..324bf35ec4dd 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -5201,7 +5201,6 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
 out_err:
 	if (parent) {
 		rbd_dev_unparent(rbd_dev);
-		kfree(rbd_dev->header_name);
 		rbd_dev_destroy(parent);
 	} else {
 		rbd_put_client(rbdc);
-- 
1.9.3

Re: [PATCH] rbd: fix double free on rbd_dev->header_name

[Alex Elder]

On 08/31/2015 07:47 AM, Ilya Dryomov wrote:
> If rbd_dev_image_probe() in rbd_dev_probe_parent() fails, header_name
> is freed twice: once in rbd_dev_probe_parent() and then in its caller
> rbd_dev_image_probe() (rbd_dev_image_probe() is called recursively to
> handle parent images).
> 
> rbd_dev_probe_parent() is responsible for probing the parent, so it
> shoudn't mock with clone's fields.

Agreed.  (But I think you mean "muck with.")  The other
argument is that the caller is who allocated it (via
rbd_dev_header_name()), so it should be responsible for
freeing it.

Reviewed-by: Alex Elder <elder@linaro.org>

> 
> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
> ---
>  drivers/block/rbd.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index bc67a93aa4f4..324bf35ec4dd 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -5201,7 +5201,6 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
>  out_err:
>  	if (parent) {
>  		rbd_dev_unparent(rbd_dev);
> -		kfree(rbd_dev->header_name);
>  		rbd_dev_destroy(parent);
>  	} else {
>  		rbd_put_client(rbdc);
>