From 1a9dc2ed5fe6a15bc57603340b739ffe4006db1f Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Fri, 4 Oct 2019 13:22:51 +0300 Subject: [PATCH] drm/i810: Prevent underflow in ioctl 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 Reviewed-by: Chris Wilson Signed-off-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20191004102251.GC823@mwanda Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- 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 d91856779beb..70de29f4e2b4 100644 --- a/drivers/gpu/drm/i810/i810_dma.c +++ b/drivers/gpu/drm/i810/i810_dma.c @@ -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;