linux-kernel - [PATCH 4.2.y-ckt 74/93] drm/radeon: forbid mapping of userptr bo through radeon device file

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Message-Id: <1461694653-29506-75-git-send-email-kamal@canonical.com>
Date:	Tue, 26 Apr 2016 11:17:14 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jérôme Glisse <jglisse@...hat.com>,
	Alex Deucher <alexander.deucher@....com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 74/93] drm/radeon: forbid mapping of userptr bo through radeon device file

4.2.8-ckt9 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= <jglisse@...hat.com>

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.

Reviewed-by: Christian König <christian.koenig@....com>
Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/gpu/drm/radeon/radeon_ttm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index fa6f041..07625aa 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -235,6 +235,8 @@ static int radeon_verify_access(struct ttm_buffer_object *bo, struct file *filp)
 {
 	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);
 }
 
-- 
2.7.4