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Tsirkin" To: Cong Zhang Cc: Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Paolo Bonzini , Stefan Hajnoczi , Jens Axboe , linux-arm-msm@vger.kernel.org, virtualization@lists.linux.dev, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, pavan.kondeti@oss.qualcomm.com Subject: Re: [PATCH] virtio_blk: NULL out vqs to avoid double free on failed resume Message-ID: <20251021085030-mutt-send-email-mst@kernel.org> References: <20251021-virtio_double_free-v1-1-4dd0cfd258f1@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251021-virtio_double_free-v1-1-4dd0cfd258f1@oss.qualcomm.com> On Tue, Oct 21, 2025 at 07:07:56PM +0800, Cong Zhang wrote: > The vblk->vqs releases during freeze. If resume fails before vblk->vqs > is allocated, later freeze/remove may attempt to free vqs again. > Set vblk->vqs to NULL after freeing to avoid double free. > > Signed-off-by: Cong Zhang > --- > The patch fixes a double free issue that occurs in virtio_blk during > freeze/resume. > The issue is caused by: > 1. During the first freeze, vblk->vqs is freed but pointer is not set to > NULL. > 2. Virtio block device fails before vblk->vqs is allocated during resume. > 3. During the next freeze, vblk->vqs gets freed again, causing the > double free crash. this part I don't get. if restore fails, how can freeze be called again? > --- > drivers/block/virtio_blk.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index f061420dfb10c40b21765b173fab7046aa447506..746795066d7f56a01c9a9c0344d24f9fa06841eb 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -1026,8 +1026,13 @@ static int init_vq(struct virtio_blk *vblk) > out: > kfree(vqs); > kfree(vqs_info); > - if (err) > + if (err) { > kfree(vblk->vqs); > + /* > + * Set to NULL to prevent freeing vqs again during freezing. > + */ > + vblk->vqs = NULL; > + } > return err; > } > > @@ -1598,6 +1603,12 @@ static int virtblk_freeze_priv(struct virtio_device *vdev) > > vdev->config->del_vqs(vdev); > kfree(vblk->vqs); > + /* > + * Set to NULL to prevent freeing vqs again after a failed vqs > + * allocation during resume. Note that kfree() already handles NULL > + * pointers safely. > + */ > + vblk->vqs = NULL; > > return 0; > } > > --- > base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb > change-id: 20250926-virtio_double_free-7ab880d82a17 > > Best regards, > -- > Cong Zhang