On 20/01/26 16:11, Matthew Auld wrote:
On 08/01/2026 11:32, Sanjay Yadav wrote:
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: <[email protected]> # v6.7+
Cc: Christian König <[email protected]>
Cc: Arunpravin Paneer Selvam <[email protected]>
Suggested-by: Matthew Auld <[email protected]>
Signed-off-by: Sanjay Yadav <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
Reviewed-by: Arunpravin Paneer Selvam <[email protected]>
Arun/Christian, when you get a chance could you also merge these two
please?
I have merged these 2 patches as well.
Regards,
Arun.
---
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);
