Patch "drm/radeon: forbid mapping of userptr bo through radeon device file" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

drm/radeon: forbid mapping of userptr bo through radeon device file

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-radeon-forbid-mapping-of-userptr-bo-through-radeon-device-file.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= <[email protected]>
Date: Tue, 19 Apr 2016 09:07:50 -0400
Subject: drm/radeon: forbid mapping of userptr bo through radeon device file
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From: Jérôme Glisse <[email protected]>

commit b5dcec693f87cb8475f2291c0075b2422addd3d6 upstream.

Allowing userptr bo which are basicly a list of page from some vma (so either anonymous page or file backed page) would lead to serious corruption of kernel structures and counters (because we overwrite the page->mapping field when mapping buffer).

This will already block if the buffer was populated before anyone does try to mmap it because then TTM_PAGE_FLAG_SG would be set in in the ttm_tt flags. But that flag is check before ttm_tt_populate in the ttm vm fault handler.

So to be safe just add a check to verify_access() callback.

---
 drivers/gpu/drm/radeon/radeon_ttm.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -235,6 +235,8 @@ static int radeon_verify_access(struct t
 {
 	struct radeon_bo *rbo = container_of(bo, struct radeon_bo, tbo);
 
+	if (radeon_ttm_tt_has_userptr(bo->ttm))
+		return -EPERM;
 	return drm_vma_node_verify_access(&rbo->gem_base.vma_node, filp);
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drm-radeon-forbid-mapping-of-userptr-bo-through-radeon-device-file.patch