[PATCH v3] media: platform: mtk-mdp3: Add missing check and free for ida_alloc

[PATCH v3] 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@iscas.ac.cn>
---
Changelog:

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 | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
index 5f74ea3b7a52..a2d204e90aa4 100644
--- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
+++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
@@ -567,6 +567,11 @@ static int mdp_m2m_open(struct file *file)
 	}
 
 	ctx->id = ida_alloc(&mdp->mdp_ida, GFP_KERNEL);
+	if (ctx->id < 0) {
+		ret = ctx->id;
+		goto err_unlock_mutex;
+	}
+
 	ctx->mdp_dev = mdp;
 
 	v4l2_fh_init(&ctx->fh, vdev);
@@ -617,6 +622,8 @@ 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

Re: [PATCH v3] media: platform: mtk-mdp3: Add missing check and free for ida_alloc

[AngeloGioacchino Del Regno]

Il 09/02/23 10:25, Jiasheng Jiang ha scritto:
> 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@iscas.ac.cn>
> ---
> Changelog:
> 
> 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 | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
> index 5f74ea3b7a52..a2d204e90aa4 100644
> --- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
> +++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
> @@ -567,6 +567,11 @@ static int mdp_m2m_open(struct file *file)
>   	}
>   
>   	ctx->id = ida_alloc(&mdp->mdp_ida, GFP_KERNEL);
> +	if (ctx->id < 0) {

There's one main not-so-minor issue here: ctx->id is u32.
Unsigned types cannot evaluate less than zero: they're .. unsigned!

There's your fix:
	ret = ida_alloc ...
	if (ret)
		....
	ctx->id = ret;


Enjoy.

Regards,
Angelo