On 03/13/2015 01:21 PM, Mika Kuoppala wrote:
vmap_batch() calculates amount of needed pages for the mapping
we are going to create. And it uses this page count as an
argument for the for_each_sg_pages() macro. The macro takes the number
of sg list entities as an argument, not the page count. So we ended
up iterating through all the pages on the mapped object, corrupting
memory past the smaller pages[] array.
Fix this by bailing out when we have enough pages.
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_cmd_parser.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 9a6da35..61ae8ff 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -836,8 +836,11 @@ static u32 *vmap_batch(struct drm_i915_gem_object *obj,
}
i = 0;
- for_each_sg_page(obj->pages->sgl, &sg_iter, npages, first_page)
+ for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, first_page) {
pages[i++] = sg_page_iter_page(&sg_iter);
+ if (i == npages)
+ break;
+ }
Are you sure this manual check is needed now that you fixed
for_each_sg_page?
Pages array looks pessimistically big enough so I don't see that memory
was getting overwritten. It looks more like our sg table was not
properly terminated which made for_each_sg_page go into random memory
and return random page pointers.
Regards,
Tvrtko
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