[PATCH 3.16 018/129] drm: Fix error handling in drm_legacy_addctx

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

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

From: YueHaibing <yuehaibing@xxxxxxxxxx>

commit c39191feed4540fed98badeb484833dcf659bb96 upstream.

'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@xxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20181229024907.12852-1-yuehaibing@xxxxxxxxxx
[bwh: Backported to 3.16: We only have the "legacy" driver type here]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_context.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/gpu/drm/drm_context.c
+++ b/drivers/gpu/drm/drm_context.c
@@ -309,19 +309,22 @@ int drm_addctx(struct drm_device *dev, v
 {
 	struct drm_ctx_list *ctx_entry;
 	struct drm_ctx *ctx = data;
+	int tmp_handle;
 
-	ctx->handle = drm_ctxbitmap_next(dev);
-	if (ctx->handle == DRM_KERNEL_CONTEXT) {
+	tmp_handle = drm_ctxbitmap_next(dev);
+	if (tmp_handle == DRM_KERNEL_CONTEXT) {
 		/* Skip kernel's context and get a new one. */
-		ctx->handle = drm_ctxbitmap_next(dev);
+		tmp_handle = drm_ctxbitmap_next(dev);
 	}
-	DRM_DEBUG("%d\n", ctx->handle);
-	if (ctx->handle < 0) {
+	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");