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

Alex Williamson
2021-06-22T20:39:35Z

On Tue, 22 Jun 2021 15:58:24 -0300
Jason Gunthorpe <jgg@ziepe.ca> wrote:

> 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:

Discrete fix above as a follow-up patch and later add the below as an
exit path cleanup, if you'd like to post it separately, seems like the
way to go to me. Thanks,

Alex

> 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)
>