Stefano Garzarella
2021-Feb-05 09:16 UTC
[PATCH v3 09/13] vhost/vdpa: remove vhost_vdpa_config_validate()
On Fri, Feb 05, 2021 at 11:27:32AM +0800, Jason Wang wrote:> >On 2021/2/5 ??1:22, Stefano Garzarella wrote: >>get_config() and set_config() callbacks in the 'struct vdpa_config_ops' >>usually already validated the inputs. Also now they can return an error, >>so we don't need to validate them here anymore. >> >>Let's use the return value of these callbacks and return it in case of >>error in vhost_vdpa_get_config() and vhost_vdpa_set_config(). >> >>Originally-by: Xie Yongji <xieyongji at bytedance.com> >>Signed-off-by: Stefano Garzarella <sgarzare at redhat.com> >>--- >> drivers/vhost/vdpa.c | 41 +++++++++++++---------------------------- >> 1 file changed, 13 insertions(+), 28 deletions(-) >> >>diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c >>index ef688c8c0e0e..d61e779000a8 100644 >>--- a/drivers/vhost/vdpa.c >>+++ b/drivers/vhost/vdpa.c >>@@ -185,51 +185,35 @@ static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp) >> return 0; >> } >>-static int vhost_vdpa_config_validate(struct vhost_vdpa *v, >>- struct vhost_vdpa_config *c) >>-{ >>- long size = 0; >>- >>- switch (v->virtio_id) { >>- case VIRTIO_ID_NET: >>- size = sizeof(struct virtio_net_config); >>- break; >>- } >>- >>- if (c->len == 0) >>- return -EINVAL; >>- >>- if (c->len > size - c->off) >>- return -E2BIG; >>- >>- return 0; >>-} >>- >> static long vhost_vdpa_get_config(struct vhost_vdpa *v, >> struct vhost_vdpa_config __user *c) >> { >> struct vdpa_device *vdpa = v->vdpa; >> struct vhost_vdpa_config config; >> unsigned long size = offsetof(struct vhost_vdpa_config, buf); >>+ long ret; >> u8 *buf; >> if (copy_from_user(&config, c, size)) >> return -EFAULT; >>- if (vhost_vdpa_config_validate(v, &config)) >>+ if (config.len == 0) >> return -EINVAL; >> buf = kvzalloc(config.len, GFP_KERNEL); > > >Then it means usersapce can allocate a very large memory.Good point.> >Rethink about this, we should limit the size here (e.g PAGE_SIZE) or >fetch the config size first (either through a config ops as you >suggested or a variable in the vdpa device that is initialized during >device creation).Maybe PAGE_SIZE is okay as a limit. If instead we want to fetch the config size, then better a config ops in my opinion, to avoid adding a new parameter to __vdpa_alloc_device(). I vote for PAGE_SIZE, but it isn't a strong opinion. What do you and @Michael suggest? Thanks, Stefano
Michael S. Tsirkin
2021-Feb-05 13:32 UTC
[PATCH v3 09/13] vhost/vdpa: remove vhost_vdpa_config_validate()
On Fri, Feb 05, 2021 at 10:16:51AM +0100, Stefano Garzarella wrote:> On Fri, Feb 05, 2021 at 11:27:32AM +0800, Jason Wang wrote: > > > > On 2021/2/5 ??1:22, Stefano Garzarella wrote: > > > get_config() and set_config() callbacks in the 'struct vdpa_config_ops' > > > usually already validated the inputs. Also now they can return an error, > > > so we don't need to validate them here anymore. > > > > > > Let's use the return value of these callbacks and return it in case of > > > error in vhost_vdpa_get_config() and vhost_vdpa_set_config(). > > > > > > Originally-by: Xie Yongji <xieyongji at bytedance.com> > > > Signed-off-by: Stefano Garzarella <sgarzare at redhat.com> > > > --- > > > drivers/vhost/vdpa.c | 41 +++++++++++++---------------------------- > > > 1 file changed, 13 insertions(+), 28 deletions(-) > > > > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > > > index ef688c8c0e0e..d61e779000a8 100644 > > > --- a/drivers/vhost/vdpa.c > > > +++ b/drivers/vhost/vdpa.c > > > @@ -185,51 +185,35 @@ static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp) > > > return 0; > > > } > > > -static int vhost_vdpa_config_validate(struct vhost_vdpa *v, > > > - struct vhost_vdpa_config *c) > > > -{ > > > - long size = 0; > > > - > > > - switch (v->virtio_id) { > > > - case VIRTIO_ID_NET: > > > - size = sizeof(struct virtio_net_config); > > > - break; > > > - } > > > - > > > - if (c->len == 0) > > > - return -EINVAL; > > > - > > > - if (c->len > size - c->off) > > > - return -E2BIG; > > > - > > > - return 0; > > > -} > > > - > > > static long vhost_vdpa_get_config(struct vhost_vdpa *v, > > > struct vhost_vdpa_config __user *c) > > > { > > > struct vdpa_device *vdpa = v->vdpa; > > > struct vhost_vdpa_config config; > > > unsigned long size = offsetof(struct vhost_vdpa_config, buf); > > > + long ret; > > > u8 *buf; > > > if (copy_from_user(&config, c, size)) > > > return -EFAULT; > > > - if (vhost_vdpa_config_validate(v, &config)) > > > + if (config.len == 0) > > > return -EINVAL; > > > buf = kvzalloc(config.len, GFP_KERNEL); > > > > > > Then it means usersapce can allocate a very large memory. > > Good point. > > > > > Rethink about this, we should limit the size here (e.g PAGE_SIZE) or > > fetch the config size first (either through a config ops as you > > suggested or a variable in the vdpa device that is initialized during > > device creation). > > Maybe PAGE_SIZE is okay as a limit. > > If instead we want to fetch the config size, then better a config ops in my > opinion, to avoid adding a new parameter to __vdpa_alloc_device(). > > I vote for PAGE_SIZE, but it isn't a strong opinion. > > What do you and @Michael suggest? > > Thanks, > StefanoDevices know what the config size is. Just have them provide it. -- MST