Re: [PATCH][next] vfio/mdpy: Fix memory leak of object mdev_state->vconfig

Jason Gunthorpe
2021-06-22T18:58:30Z

On Tue, Jun 22, 2021 at 07:37:10PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> In the case where the call to vfio_register_group_dev fails the error
> return path kfree's mdev_state but not mdev_state->vconfig. Fix this
> by kfree'ing mdev_state->vconfig before returning.
>
> Addresses-Coverity: ("Resource leak")
> Fixes: 437e41368c01 ("vfio/mdpy: Convert to use vfio_register_group_dev()")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> samples/vfio-mdev/mdpy.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index 7e9c9df0f05b..393c9df6f6a0 100644
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -261,6 +261,7 @@ static int mdpy_probe(struct mdev_device *mdev)
>
> ret = vfio_register_group_dev(&mdev_state->vdev);
> if (ret) {
> + kfree(mdev_state->vconfig);
> kfree(mdev_state);
> return ret;
> }

Thanks Colin, looks right

Alex, this is in your hch-mdev-direct-v4 branch can you squash or
whatever?

Though if we are touching this I prefer the below:

diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 7e9c9df0f05bac..868a0e7fa90e98 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -235,17 +235,16 @@ static int mdpy_probe(struct mdev_device *mdev)

mdev_state->vconfig = kzalloc(MDPY_CONFIG_SPACE_SIZE, GFP_KERNEL);
if (mdev_state->vconfig == NULL) {
- kfree(mdev_state);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto err_state;
}

fbsize = roundup_pow_of_two(type->width * type->height * type->bytepp);

mdev_state->memblk = vmalloc_user(fbsize);
if (!mdev_state->memblk) {
- kfree(mdev_state->vconfig);
- kfree(mdev_state);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto err_vconfig;
}
dev_info(dev, "%s: %s (%dx%d)\n", __func__, type->name, type->width,
type->height);
@@ -260,12 +259,17 @@ static int mdpy_probe(struct mdev_device *mdev)
mdpy_count++;

ret = vfio_register_group_dev(&mdev_state->vdev);
- if (ret) {
- kfree(mdev_state);
- return ret;
- }
+ if (ret)
+ goto err_vconfig;
+
dev_set_drvdata(&mdev->dev, mdev_state);
return 0;
+
+err_vconfig:
+ kfree(mdev_state->vconfig);
+err_state:
+ kfree(mdev_state);
+ return ret;
}

static void mdpy_remove(struct mdev_device *mdev)