[PATCH v3] vduse: vduse: check that offsets are within bounds

[PATCH v3] vduse: vduse: check that offsets are within bounds

[Dan Carpenter]

In vduse_dev_ioctl(), the "config.offset" comes from the user.  There
needs to a check to prevent it being out of bounds.  The "config.offset"
and "dev->config_size" variables are both type u32.  So if the offset is
out of bounds then the "dev->config_size - config.offset" subtraction
results in a very high u32 value.

The vhost_vdpa_config_validate() function has a similar issue, but there
the "size" is long type so the subtraction works on 64bit system and
this change only affects 32bit systems.

Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: the first version had a reversed if statement
v3: fix vhost_vdpa_config_validate() as pointed out by Yongji Xie.

 drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
 drivers/vhost/vdpa.c               | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index c9204c62f339..1a206f95d73a 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -975,7 +975,8 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 			break;
 
 		ret = -EINVAL;
-		if (config.length == 0 ||
+		if (config.offset > dev->config_size ||
+		    config.length == 0 ||
 		    config.length > dev->config_size - config.offset)
 			break;
 
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 29cced1cd277..e3c4f059b21a 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -197,7 +197,7 @@ static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
 	struct vdpa_device *vdpa = v->vdpa;
 	long size = vdpa->config->get_config_size(vdpa);
 
-	if (c->len == 0)
+	if (c->len == 0 || c->off > size)
 		return -EINVAL;
 
 	if (c->len > size - c->off)
-- 
2.20.1

Re: [PATCH v3] vduse: vduse: check that offsets are within bounds

[Jason Wang]

On Tue, Dec 7, 2021 at 7:49 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> In vduse_dev_ioctl(), the "config.offset" comes from the user.  There
> needs to a check to prevent it being out of bounds.  The "config.offset"
> and "dev->config_size" variables are both type u32.  So if the offset is
> out of bounds then the "dev->config_size - config.offset" subtraction
> results in a very high u32 value.
>
> The vhost_vdpa_config_validate() function has a similar issue, but there
> the "size" is long type so the subtraction works on 64bit system and
> this change only affects 32bit systems.
>
> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Stable candidate.

Patch looks good to me but I think we need to use separate patches to
ease the backporting.

Thanks

> ---
> v2: the first version had a reversed if statement
> v3: fix vhost_vdpa_config_validate() as pointed out by Yongji Xie.
>
>  drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
>  drivers/vhost/vdpa.c               | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index c9204c62f339..1a206f95d73a 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -975,7 +975,8 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>                         break;
>
>                 ret = -EINVAL;
> -               if (config.length == 0 ||
> +               if (config.offset > dev->config_size ||
> +                   config.length == 0 ||
>                     config.length > dev->config_size - config.offset)
>                         break;
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 29cced1cd277..e3c4f059b21a 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -197,7 +197,7 @@ static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
>         struct vdpa_device *vdpa = v->vdpa;
>         long size = vdpa->config->get_config_size(vdpa);
>
> -       if (c->len == 0)
> +       if (c->len == 0 || c->off > size)
>                 return -EINVAL;
>
>         if (c->len > size - c->off)
> --
> 2.20.1
>