Should also note that it’s currently possible to overflow usize::MAX here which causes a panic. This patch is also addressing that by moving the overflow check to before the page alignment. If a request from user-space is made for a size that is Within one PAGE_SIZE of usize::MAX, then it will panic when we try to use size.next_multiple_of().
So even if we want to keep the 4k page alignments regardless of the underlying CPU architecture, we should at least do the Overflow check, and use page_align() instead of next_multiple_of(). > On 21 Nov 2025, at 2:04 pm, [email protected] wrote: > > Use page::page_align for GEM object memory allocation to ensure the > allocation is page aligned. This ensures that the allocation is page > aligned with the system in cases where 4096 is not the default. > For example on 16k or 64k aarch64 systems this allocation should be > aligned accordingly. > > Signed-off-by: Brendan Shephard <[email protected]> > --- > drivers/gpu/drm/nova/gem.rs | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs > index 2760ba4f3450..a07e922e25ef 100644 > --- a/drivers/gpu/drm/nova/gem.rs > +++ b/drivers/gpu/drm/nova/gem.rs > @@ -3,6 +3,10 @@ > use kernel::{ > drm, > drm::{gem, gem::BaseObject}, > + page::{ > + page_align, > + PAGE_SIZE, // > + }, > prelude::*, > sync::aref::ARef, > }; > @@ -27,12 +31,13 @@ fn new(_dev: &NovaDevice, _size: usize) -> impl > PinInit<Self, Error> { > impl NovaObject { > /// Create a new DRM GEM object. > pub(crate) fn new(dev: &NovaDevice, size: usize) -> > Result<ARef<gem::Object<Self>>> { > - let aligned_size = size.next_multiple_of(1 << 12); > - > - if size == 0 || size > aligned_size { > + // Check for 0 size or potential usize overflow before calling > page_align > + if size == 0 || size > usize::MAX - PAGE_SIZE + 1 { > return Err(EINVAL); > } > > + let aligned_size = page_align(size); > + > gem::Object::new(dev, aligned_size) > } > > --
