drm: Fix error handling in drm_legacy_addctx

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit c39191feed4540fed98badeb484833dcf659bb96 ]

'ctx->handle' is unsigned, it never less than zero.
This patch use int 'tmp_handle' to handle the err condition.

Fixes: 62968144e673 ("drm: convert drm context code to use Linux idr")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181229024907.12852-1-yuehaibing@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
index 3c4000facb360a012f78b12599d918a276145ca6..da5abf24f59ff7f02181a88f8452828473600532 100644 (file)
--- a/drivers/gpu/drm/drm_context.c
+++ b/drivers/gpu/drm/drm_context.c
@@ -361,23 +361,26 @@ int drm_legacy_addctx(struct drm_device *dev, void *data,
 {
        struct drm_ctx_list *ctx_entry;
        struct drm_ctx *ctx = data;
+       int tmp_handle;
 
        if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT) &&
            !drm_core_check_feature(dev, DRIVER_LEGACY))
                return -EINVAL;
 
-       ctx->handle = drm_legacy_ctxbitmap_next(dev);
-       if (ctx->handle == DRM_KERNEL_CONTEXT) {
+       tmp_handle = drm_legacy_ctxbitmap_next(dev);
+       if (tmp_handle == DRM_KERNEL_CONTEXT) {
                /* Skip kernel's context and get a new one. */
-               ctx->handle = drm_legacy_ctxbitmap_next(dev);
+               tmp_handle = drm_legacy_ctxbitmap_next(dev);
        }
-       DRM_DEBUG("%d\n", ctx->handle);
-       if (ctx->handle == -1) {
+       DRM_DEBUG("%d\n", tmp_handle);
+       if (tmp_handle < 0) {
                DRM_DEBUG("Not enough free contexts.\n");
                /* Should this return -EBUSY instead? */
-               return -ENOMEM;
+               return tmp_handle;
        }
 
+       ctx->handle = tmp_handle;
+
        ctx_entry = kmalloc(sizeof(*ctx_entry), GFP_KERNEL);
        if (!ctx_entry) {
                DRM_DEBUG("out of memory\n");