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drm/i915: Fix vmap_batch page iterator overrun 

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.

This regression has been introduced in

commit 17cabf571e
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Wed Jan 14 11:20:57 2015 +0000

    drm/i915: Trim the command parser allocations

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Mika Kuoppala 2015-03-13 15:21:53 +02:00 committed by Daniel Vetter
parent a1559ffefb
commit 72c5ba9562
1 changed files with 4 additions and 1 deletions
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5
drivers/gpu/drm/i915/i915_cmd_parser.c
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@ -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;
}
addr = vmap(pages, i, 0, PAGE_KERNEL);
if (addr == NULL) {