[PATCH 4.4 11/51] drm/vmwgfx: Limit the user-space command buffer size

From: Greg Kroah-Hartman
Date: Sat Oct 29 2016 - 10:28:10 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Thomas Hellstrom <thellstrom@xxxxxxxxxx>

commit 51ab70bed997f64f091a639dbe22b629725a7faf upstream.

With older hardware versions, the user could specify arbitrarily large
command buffer sizes, causing a vmalloc / vmap space exhaustion.

Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Reviewed-by: Brian Paul <brianp@xxxxxxxxxx>
Reviewed-by: Sinclair Yeh <syeh@xxxxxxxxxx>
Signed-off-by: Sinclair Yeh <syeh@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -3830,14 +3830,14 @@ static void *vmw_execbuf_cmdbuf(struct v
int ret;

*header = NULL;
- if (!dev_priv->cman || kernel_commands)
- return kernel_commands;
-
if (command_size > SVGA_CB_MAX_SIZE) {
DRM_ERROR("Command buffer is too large.\n");
return ERR_PTR(-EINVAL);
}

+ if (!dev_priv->cman || kernel_commands)
+ return kernel_commands;
+
/* If possible, add a little space for fencing. */
cmdbuf_size = command_size + 512;
cmdbuf_size = min_t(size_t, cmdbuf_size, SVGA_CB_MAX_SIZE);