[PATCH v2 1/2] drm/buddy: Fix alloc_range() error handling code

[Arunpravin Paneer Selvam]

Few users have observed display corruption when they boot
the machine to KDE Plasma or playing games. We have root
caused the problem that whenever alloc_range() couldn't
find the required memory blocks the function was returning
SUCCESS in some of the corner cases.

The right approach would be if the total allocated size
is less than the required size, the function should
return -ENOSPC.

Cc: <stable at vger.kernel.org> # 6.7+
Fixes: 0a1844bf0b53 ("drm/buddy: Improve contiguous memory allocation")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3097
Tested-by: Mario Limonciello <mario.limonciello at amd.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240207174456.341121-1-Arunpravin.PaneerSelvam@amd.com/
Acked-by: Christian König <christian.koenig at amd.com>
Reviewed-by: Matthew Auld <matthew.auld at intel.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam at amd.com>
---
 drivers/gpu/drm/drm_buddy.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index f57e6d74fb0e..c1a99bf4dffd 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -539,6 +539,12 @@ static int __alloc_range(struct drm_buddy *mm,
 	} while (1);
 
 	list_splice_tail(&allocated, blocks);
+
+	if (total_allocated < size) {
+		err = -ENOSPC;
+		goto err_free;
+	}
+
 	return 0;
 
 err_undo:

base-commit: b6ddaa63f728d26c12048aed76be99c24f435c41
-- 
2.25.1