Re: [PATCH v2] drm: Fix a infinite loop condition when order becomes 0

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On 16/03/2022 06:34, Arunpravin Paneer Selvam wrote:
handle a situation in the condition order-- == min_order,
when order = 0 and min_order = 0, leading to order = -1,
it now won't exit the loop. To avoid this problem,
added a order check in the same condition, (i.e)
when order is 0, we return -ENOSPC

v2: use full name in email program and in Signed-off tag

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>
---
  drivers/gpu/drm/drm_buddy.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 72f52f293249..5ab66aaf2bbd 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -685,7 +685,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
  			if (!IS_ERR(block))
  				break;
- if (order-- == min_order) {
+			if (!order || order-- == min_order) {

It shouldn't be possible to enter an infinite loop here, without first tripping up the BUG_ON(order < min_order) further up, and for that, as we discussed here[1], it sounded like the conclusion was to rather add a simple check somewhere in drm_buddy_alloc_blocks() to reject any size not aligned to the min_page_size?

[1] https://patchwork.freedesktop.org/patch/477414/?series=101108&rev=1

  				err = -ENOSPC;
  				goto err_free;
  			}

base-commit: 3bd60c0259406c5ca3ce5cdc958fb910ad4b8175



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