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drm/i810: Prevent underflow in ioctl

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commit 4f69851fbaa26b155330be35ce8ac393e93e7442 upstream.

The "used" variables here come from the user in the ioctl and it can be
negative.  It could result in an out of bounds write.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004102251.GC823@mwanda
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dan Carpenter 2019-10-04 13:22:51 +03:00 committed by Greg Kroah-Hartman
parent 799a03be21
commit 1a9dc2ed5f
1 changed files with 2 additions and 2 deletions
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4
drivers/gpu/drm/i810/i810_dma.c
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@ -723,7 +723,7 @@ static void i810_dma_dispatch_vertex(struct drm_device *dev,
if (nbox > I810_NR_SAREA_CLIPRECTS)
nbox = I810_NR_SAREA_CLIPRECTS;
if (used > 4 * 1024)
if (used < 0 || used > 4 * 1024)
used = 0;
if (sarea_priv->dirty)
@ -1043,7 +1043,7 @@ static void i810_dma_dispatch_mc(struct drm_device *dev, struct drm_buf *buf, in
if (u != I810_BUF_CLIENT)
DRM_DEBUG("MC found buffer that isn't mine!\n");
if (used > 4 * 1024)
if (used < 0 || used > 4 * 1024)
used = 0;
sarea_priv->dirty = 0x7f;