[PATCH v4] media: platform: mtk-mdp3: Add missing check and free for ida_alloc

[Jiasheng Jiang]

Add the check for the return value of the ida_alloc in order to avoid
NULL pointer dereference.
Moreover, free allocated "ctx->id" if mdp_m2m_open fails later in order
to avoid memory leak.

Fixes: 61890ccaefaf ("media: platform: mtk-mdp3: add MediaTek MDP3 driver")
Signed-off-by: Jiasheng Jiang <jiasheng at iscas.ac.cn>
---
Changelog:

v3 -> v4

1. Use ret to check the return value.

v2 -> v3:

1. Fix the goto label.

v1 -> v2:

1. Fix the check for the ida_alloc.
---
 drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
index 5f74ea3b7a52..8612a48bde10 100644
--- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
+++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
@@ -566,7 +566,11 @@ static int mdp_m2m_open(struct file *file)
 		goto err_free_ctx;
 	}
 
-	ctx->id = ida_alloc(&mdp->mdp_ida, GFP_KERNEL);
+	ret = ida_alloc(&mdp->mdp_ida, GFP_KERNEL);
+	if (ret < 0)
+		goto err_unlock_mutex;
+	ctx->id = ret;
+
 	ctx->mdp_dev = mdp;
 
 	v4l2_fh_init(&ctx->fh, vdev);
@@ -617,6 +621,8 @@ static int mdp_m2m_open(struct file *file)
 	v4l2_fh_del(&ctx->fh);
 err_exit_fh:
 	v4l2_fh_exit(&ctx->fh);
+	ida_free(&mdp->mdp_ida, ctx->id);
+err_unlock_mutex:
 	mutex_unlock(&mdp->m2m_lock);
 err_free_ctx:
 	kfree(ctx);
-- 
2.25.1