[PATCH] drm/i810: Prevent underflow in ioctl
From: Dan Carpenter
Date: Fri Oct 04 2019 - 06:23:24 EST
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@xxxxxxxxxx>
---
drivers/gpu/drm/i810/i810_dma.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i810/i810_dma.c b/drivers/gpu/drm/i810/i810_dma.c
index 2a77823b8e9a..e66c38332df4 100644
--- a/drivers/gpu/drm/i810/i810_dma.c
+++ b/drivers/gpu/drm/i810/i810_dma.c
@@ -728,7 +728,7 @@ 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)
@@ -1048,7 +1048,7 @@ 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;
--
2.20.1