[PATCH] drm/mediatek: Fix potential NULL dereference in mtk_crtc_destroy()

[PATCH] drm/mediatek: Fix potential NULL dereference in mtk_crtc_destroy()

[Dan Carpenter]

In mtk_crtc_create(), if the call to mbox_request_channel() fails then we
set the "mtk_crtc->cmdq_client.chan" pointer to NULL.  In that situation,
we do not call cmdq_pkt_create().

During the cleanup, we need to check if the "mtk_crtc->cmdq_client.chan"
is NULL first before calling cmdq_pkt_destroy().  Calling
cmdq_pkt_destroy() is unnecessary if we didn't call cmdq_pkt_create() and
it will result in a NULL pointer dereference.

Fixes: 7627122fd1c0 ("drm/mediatek: Add cmdq_handle in mtk_crtc")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
 drivers/gpu/drm/mediatek/mtk_crtc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
index 175b00e5a253..c15013792583 100644
--- a/drivers/gpu/drm/mediatek/mtk_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
@@ -127,9 +127,8 @@ static void mtk_crtc_destroy(struct drm_crtc *crtc)
 
 	mtk_mutex_put(mtk_crtc->mutex);
 #if IS_REACHABLE(CONFIG_MTK_CMDQ)
-	cmdq_pkt_destroy(&mtk_crtc->cmdq_client, &mtk_crtc->cmdq_handle);
-
 	if (mtk_crtc->cmdq_client.chan) {
+		cmdq_pkt_destroy(&mtk_crtc->cmdq_client, &mtk_crtc->cmdq_handle);
 		mbox_free_channel(mtk_crtc->cmdq_client.chan);
 		mtk_crtc->cmdq_client.chan = NULL;
 	}
-- 
2.45.2

Re: [PATCH] drm/mediatek: Fix potential NULL dereference in mtk_crtc_destroy()

[AngeloGioacchino Del Regno]

Il 12/09/24 10:44, Dan Carpenter ha scritto:
> In mtk_crtc_create(), if the call to mbox_request_channel() fails then we
> set the "mtk_crtc->cmdq_client.chan" pointer to NULL.  In that situation,
> we do not call cmdq_pkt_create().
> 
> During the cleanup, we need to check if the "mtk_crtc->cmdq_client.chan"
> is NULL first before calling cmdq_pkt_destroy().  Calling
> cmdq_pkt_destroy() is unnecessary if we didn't call cmdq_pkt_create() and
> it will result in a NULL pointer dereference.
> 
> Fixes: 7627122fd1c0 ("drm/mediatek: Add cmdq_handle in mtk_crtc")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Re: [PATCH] drm/mediatek: Fix potential NULL dereference in mtk_crtc_destroy()

[CK Hu (胡俊光)]

Hi, Dan:

On Thu, 2024-09-12 at 11:44 +0300, Dan Carpenter wrote:
>  	 
> External email : Please do not click links or open attachments until you have verified the sender or the content.
>  In mtk_crtc_create(), if the call to mbox_request_channel() fails then we
> set the "mtk_crtc->cmdq_client.chan" pointer to NULL.  In that situation,
> we do not call cmdq_pkt_create().
> 
> During the cleanup, we need to check if the "mtk_crtc->cmdq_client.chan"
> is NULL first before calling cmdq_pkt_destroy().  Calling
> cmdq_pkt_destroy() is unnecessary if we didn't call cmdq_pkt_create() and
> it will result in a NULL pointer dereference.

Reviewed-by: CK Hu <ck.hu@mediatek.com>

> 
> Fixes: 7627122fd1c0 ("drm/mediatek: Add cmdq_handle in mtk_crtc")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_crtc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
> index 175b00e5a253..c15013792583 100644
> --- a/drivers/gpu/drm/mediatek/mtk_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
> @@ -127,9 +127,8 @@ static void mtk_crtc_destroy(struct drm_crtc *crtc)
>  
>  mtk_mutex_put(mtk_crtc->mutex);
>  #if IS_REACHABLE(CONFIG_MTK_CMDQ)
> -cmdq_pkt_destroy(&mtk_crtc->cmdq_client, &mtk_crtc->cmdq_handle);
> -
>  if (mtk_crtc->cmdq_client.chan) {
> +cmdq_pkt_destroy(&mtk_crtc->cmdq_client, &mtk_crtc->cmdq_handle);
>  mbox_free_channel(mtk_crtc->cmdq_client.chan);
>  mtk_crtc->cmdq_client.chan = NULL;
>  }
> -- 
> 2.45.2
> 
> 

Re: [PATCH] drm/mediatek: Fix potential NULL dereference in mtk_crtc_destroy()

[Chun-Kuang Hu]

Hi, Dan:

Dan Carpenter <dan.carpenter@linaro.org> 於 2024年9月12日 週四 下午4:45寫道：
>
> In mtk_crtc_create(), if the call to mbox_request_channel() fails then we
> set the "mtk_crtc->cmdq_client.chan" pointer to NULL.  In that situation,
> we do not call cmdq_pkt_create().
>
> During the cleanup, we need to check if the "mtk_crtc->cmdq_client.chan"
> is NULL first before calling cmdq_pkt_destroy().  Calling
> cmdq_pkt_destroy() is unnecessary if we didn't call cmdq_pkt_create() and
> it will result in a NULL pointer dereference.

Applied to mediatek-drm-fixes [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-fixes

Regards,
Chun-Kuang.

>
> Fixes: 7627122fd1c0 ("drm/mediatek: Add cmdq_handle in mtk_crtc")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_crtc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
> index 175b00e5a253..c15013792583 100644
> --- a/drivers/gpu/drm/mediatek/mtk_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
> @@ -127,9 +127,8 @@ static void mtk_crtc_destroy(struct drm_crtc *crtc)
>
>         mtk_mutex_put(mtk_crtc->mutex);
>  #if IS_REACHABLE(CONFIG_MTK_CMDQ)
> -       cmdq_pkt_destroy(&mtk_crtc->cmdq_client, &mtk_crtc->cmdq_handle);
> -
>         if (mtk_crtc->cmdq_client.chan) {
> +               cmdq_pkt_destroy(&mtk_crtc->cmdq_client, &mtk_crtc->cmdq_handle);
>                 mbox_free_channel(mtk_crtc->cmdq_client.chan);
>                 mtk_crtc->cmdq_client.chan = NULL;
>         }
> --
> 2.45.2
>