From: Dan Carpenter Date: Fri, 4 Oct 2019 10:22:51 +0000 (+0300) Subject: drm/i810: Prevent underflow in ioctl X-Git-Tag: v5.5-rc1~128^2~31^2~9 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4f69851fbaa26b155330be35ce8ac393e93e7442;p=thirdparty%2Flinux.git drm/i810: Prevent underflow in ioctl 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 --- diff --git a/drivers/gpu/drm/i810/i810_dma.c b/drivers/gpu/drm/i810/i810_dma.c index 2a77823b8e9a2..e66c38332df47 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;