On Fri, Feb 05, 2021 at 08:32:37AM -0500, Michael S. Tsirkin wrote:

On Fri, Feb 05, 2021 at 10:16:51AM +0100, Stefano Garzarella wrote:

quoted

On Fri, Feb 05, 2021 at 11:27:32AM +0800, Jason Wang wrote:

quoted

On 2021/2/5 上午1:22, Stefano Garzarella wrote:

quoted

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 [off-list ref]
Signed-off-by: Stefano Garzarella <sgarzare@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.

quoted

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

Devices know what the config size is. Just have them provide it.

Okay, I'll add get_config_size() callback in vdpa_config_ops and I'll 
leave vhost_vdpa_config_validate() that will use that callback instead 
of 'virtio_id' to get the config size from the device.

At this point I think I can remove the "vdpa: add return value to 
get_config/set_config callbacks" patch and leave void return to 
get_config/set_config callbacks.

Does this make sense?

Thanks,
Stefano

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