linux-kernel - [PATCH 1/2] drm/vc4: Fix an integer overflow in temporary allocation layout.

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Message-Id: <20170117202050.22408-1-eric@anholt.net>
Date:   Wed, 18 Jan 2017 07:20:49 +1100
From:   Eric Anholt <eric@...olt.net>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, Eric Anholt <eric@...olt.net>
Subject: [PATCH 1/2] drm/vc4: Fix an integer overflow in temporary allocation layout.

We copy the unvalidated ioctl arguments from the user into kernel
temporary memory to run the validation from, to avoid a race where the
user updates the unvalidate contents in between validating them and
copying them into the validated BO.

However, in setting up the layout of the kernel side, we failed to
check one of the additions (the roundup() for shader_rec_offset)
against integer overflow, allowing a nearly MAX_UINT value of
bin_cl_size to cause us to under-allocate the temporary space that we
then copy_from_user into.

Reported-by: Murray McAllister <murray.mcallister@...omniasec.com>
Signed-off-by: Eric Anholt <eric@...olt.net>
Fixes: d5b1a78a772f ("drm/vc4: Add support for drawing 3D frames.")
---
 drivers/gpu/drm/vc4/vc4_gem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c
index db920771bfb5..c5fe3554858e 100644
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -594,7 +594,8 @@ vc4_get_bcl(struct drm_device *dev, struct vc4_exec_info *exec)
 					  args->shader_rec_count);
 	struct vc4_bo *bo;

-	if (uniforms_offset < shader_rec_offset ||
+	if (shader_rec_offset < args->bin_cl_size ||
+	    uniforms_offset < shader_rec_offset ||
 	    exec_size < uniforms_offset ||
 	    args->shader_rec_count >= (UINT_MAX /
 					  sizeof(struct vc4_shader_state)) ||
-- 
2.11.0