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vfio: use __aligned_u64 in struct vfio_device_gfx_plane_info

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The memory layout of struct vfio_device_gfx_plane_info is
architecture-dependent due to a u64 field and a struct size that is not
a multiple of 8 bytes:
- On x86_64 the struct size is padded to a multiple of 8 bytes.
- On x32 the struct size is only a multiple of 4 bytes, not 8.
- Other architectures may vary.

Use __aligned_u64 to make memory layout consistent. This reduces the
chance of 32-bit userspace on a 64-bit kernel breakage.

This patch increases the struct size on x32 but this is safe because of
the struct's argsz field. The kernel may grow the struct as long as it
still supports smaller argsz values from userspace (e.g. applications
compiled against older kernel headers).

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20230918205617.1478722-3-stefanha@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Stefan Hajnoczi
2023-09-18 16:56:16 -04:00
committed by Alex Williamson
parent 2f8d25fa8a
commit a7bea9f4fe
4 changed files with 5 additions and 4 deletions
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2
samples/vfio-mdev/mbochs.c
View File

@@ -1262,7 +1262,7 @@ static long mbochs_ioctl(struct vfio_device *vdev, unsigned int cmd,
case VFIO_DEVICE_QUERY_GFX_PLANE:
{
struct vfio_device_gfx_plane_info plane;
struct vfio_device_gfx_plane_info plane = {};
minsz = offsetofend(struct vfio_device_gfx_plane_info,
region_index);

2
samples/vfio-mdev/mdpy.c
View File

@@ -591,7 +591,7 @@ static long mdpy_ioctl(struct vfio_device *vdev, unsigned int cmd,
case VFIO_DEVICE_QUERY_GFX_PLANE:
{
struct vfio_device_gfx_plane_info plane;
struct vfio_device_gfx_plane_info plane = {};
minsz = offsetofend(struct vfio_device_gfx_plane_info,
region_index);