When DRM_BUDDY_CONTIGUOUS_ALLOCATION is set, the requested size is rounded up to the next power-of-two via roundup_pow_of_two(). Similarly, for non-contiguous allocations with large min_block_size, the size is aligned up via round_up(). Both operations can produce a rounded size that exceeds mm->size, which later triggers BUG_ON(order > mm->max_order).
Example scenarios: - 9G CONTIGUOUS allocation on 10G VRAM memory: roundup_pow_of_two(9G) = 16G > 10G - 9G allocation with 8G min_block_size on 10G VRAM memory: round_up(9G, 8G) = 16G > 10G
Fix this by checking the rounded size against mm->size. For non-contiguous or range allocations where size > mm->size is invalid, return -EINVAL immediately. For contiguous allocations without range restrictions, allow the request to fall through to the existing __alloc_contig_try_harder() fallback.
This ensures invalid user input returns an error or uses the fallback path instead of hitting BUG_ON.
v2: (Matt A) - Add Fixes, Cc stable, and Closes tags for context
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6712 Fixes: 0a1844bf0b53 ("drm/buddy: Improve contiguous memory allocation") Cc: stable@vger.kernel.org # v6.7+ Cc: Christian König christian.koenig@amd.com Cc: Arunpravin Paneer Selvam Arunpravin.PaneerSelvam@amd.com Suggested-by: Matthew Auld matthew.auld@intel.com Signed-off-by: Sanjay Yadav sanjay.kumar.yadav@intel.com Reviewed-by: Matthew Auld matthew.auld@intel.com Reviewed-by: Arunpravin Paneer Selvam Arunpravin.PaneerSelvam@amd.com --- drivers/gpu/drm/drm_buddy.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c index 2f279b46bd2c..5141348fc6c9 100644 --- a/drivers/gpu/drm/drm_buddy.c +++ b/drivers/gpu/drm/drm_buddy.c @@ -1155,6 +1155,15 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, order = fls(pages) - 1; min_order = ilog2(min_block_size) - ilog2(mm->chunk_size);
+ if (order > mm->max_order || size > mm->size) { + if ((flags & DRM_BUDDY_CONTIGUOUS_ALLOCATION) && + !(flags & DRM_BUDDY_RANGE_ALLOCATION)) + return __alloc_contig_try_harder(mm, original_size, + original_min_size, blocks); + + return -EINVAL; + } + do { order = min(order, (unsigned int)fls(pages) - 1); BUG_ON(order > mm->max_order);