2024-02-27 15:22:21

by Dan Carpenter

Subject: [PATCH] vduse: Fix off by one in vduse_dev_mmap()

The dev->vqs[] array has "dev->vq_num" elements. It's allocated in
vduse_dev_init_vqs(). Thus, this > comparison needs to be >= to avoid
reading one element beyond the end of the array.

Fixes: 316ecd1346b0 ("vduse: Add file operation for mmap")
Signed-off-by: Dan Carpenter <[email protected]>
---
drivers/vdpa/vdpa_user/vduse_dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index b7a1fb88c506..9150c8281953 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1532,7 +1532,7 @@ static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
if ((vma->vm_flags & VM_SHARED) == 0)
return -EINVAL;

- if (index > dev->vq_num)
+ if (index >= dev->vq_num)
return -EINVAL;

vq = dev->vqs[index];
--
2.43.0

2024-02-27 15:49:52

by Michael S. Tsirkin

Subject: Re: [PATCH] vduse: Fix off by one in vduse_dev_mmap()

On Tue, Feb 27, 2024 at 06:21:46PM +0300, Dan Carpenter wrote:
> The dev->vqs[] array has "dev->vq_num" elements. It's allocated in
> vduse_dev_init_vqs(). Thus, this > comparison needs to be >= to avoid
> reading one element beyond the end of the array.
>
> Fixes: 316ecd1346b0 ("vduse: Add file operation for mmap")
> Signed-off-by: Dan Carpenter <[email protected]>


Oh wow and does this not come from userspace? If yes we
need the speculation magic macro when using the index, do we not?

> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index b7a1fb88c506..9150c8281953 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1532,7 +1532,7 @@ static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
> if ((vma->vm_flags & VM_SHARED) == 0)
> return -EINVAL;
>
> - if (index > dev->vq_num)
> + if (index >= dev->vq_num)
> return -EINVAL;
>
> vq = dev->vqs[index];
> --
> 2.43.0

2024-02-28 17:43:19

by Dan Carpenter

Subject: Re: [PATCH] vduse: Fix off by one in vduse_dev_mmap()

On Tue, Feb 27, 2024 at 10:48:49AM -0500, Michael S. Tsirkin wrote:
> On Tue, Feb 27, 2024 at 06:21:46PM +0300, Dan Carpenter wrote:
> > The dev->vqs[] array has "dev->vq_num" elements. It's allocated in
> > vduse_dev_init_vqs(). Thus, this > comparison needs to be >= to avoid
> > reading one element beyond the end of the array.
> >
> > Fixes: 316ecd1346b0 ("vduse: Add file operation for mmap")
> > Signed-off-by: Dan Carpenter <[email protected]>
>
>
> Oh wow and does this not come from userspace? If yes we
> need the speculation magic macro when using the index, do we not?
>

Yes, it does come from userspace.

To be honest, I'm not sure about speculation. The similar places in
this file protect against speculation so, probably? I'll resend the
patch.

regards,
dan carpenter