imx-drm: imx-drm-core: improve safety of imx_drm_add_crtc()

We must not add more CRTCs than we have declared to the vblank
helpers, otherwise we overflow their arrays.  Force failure if we
exceed the number of CRTCs.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/staging/imx-drm/imx-drm-core.c b/drivers/staging/imx-drm/imx-drm-core.c
index 19e431dee493..96e4eee344ef 100644
--- a/drivers/staging/imx-drm/imx-drm-core.c
+++ b/drivers/staging/imx-drm/imx-drm-core.c
@@ -501,6 +501,15 @@ int imx_drm_add_crtc(struct drm_crtc *crtc,
 
         mutex_lock(&imxdrm->mutex);
 
+        /*
+         * The vblank arrays are dimensioned by MAX_CRTC - we can't
+         * pass IDs greater than this to those functions.
+         */
+        if (imxdrm->pipes >= MAX_CRTC) {
+                ret = -EINVAL;
+                goto err_busy;
+        }
+
         if (imxdrm->drm->open_count) {
                 ret = -EBUSY;
                 goto err_busy;