[PATCH RFC 016/111] staging: etnaviv: validation: ensure space for the LINK command

[Lucas Stach]

From: Russell King <rmk+ker...@arm.linux.org.uk>

Ensure that we reject command buffers which are fully populated, as
we always need to append two words for a LINK command to the end of
the buffer.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/staging/etnaviv/etnaviv_gem_submit.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/etnaviv/etnaviv_gem_submit.c 
b/drivers/staging/etnaviv/etnaviv_gem_submit.c
index dd87fdfe7ab5..f8b733a0e313 100644
--- a/drivers/staging/etnaviv/etnaviv_gem_submit.c
+++ b/drivers/staging/etnaviv/etnaviv_gem_submit.c
@@ -348,6 +348,7 @@ int etnaviv_ioctl_gem_submit(struct drm_device *dev, void 
*data,
                void __user *userptr =
                        to_user_ptr(args->cmds + (i * sizeof(submit_cmd)));
                struct etnaviv_gem_object *etnaviv_obj;
+               unsigned max_size;

                ret = copy_from_user(&submit_cmd, userptr, sizeof(submit_cmd));
                if (ret) {
@@ -373,8 +374,13 @@ int etnaviv_ioctl_gem_submit(struct drm_device *dev, void 
*data,
                        goto out;
                }

-               if ((submit_cmd.size + submit_cmd.submit_offset) >=
-                               etnaviv_obj->base.size) {
+               /*
+                * We must have space to add a LINK command at the end of
+                * the command buffer.
+                */
+               max_size = etnaviv_obj->base.size - 8;
+
+               if ((submit_cmd.size + submit_cmd.submit_offset) > max_size) {
                        DRM_ERROR("invalid cmdstream size: %u\n", 
submit_cmd.size);
                        ret = -EINVAL;
                        goto out;
-- 
2.1.4