> From: Stefan Hajnoczi <stefanha@xxxxxxxxxx> > Sent: Wednesday, August 30, 2023 2:27 AM > > The memory layout of struct vfio_device_ioeventfd 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 that 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). > > The code that uses struct vfio_device_ioeventfd already works correctly > when the struct size grows, so only the struct definition needs to be > changed. > > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
