drm/vmwgfx: Limit the user-space command buffer size

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@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index 4948c15298369cf4dc907b9aa07b2496441656dc..ecf15cf0c3fd49e0dbb83a16411901dd0e586281 100644 (file)
--- 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 vmw_private *dev_priv,
        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);