linux-kernel - Re: [PATCH] accel/qaic: Call DRM helper function to destroy prime GEM

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Date:   Thu, 15 Jun 2023 09:05:12 +0200
From:   Christian König <christian.koenig@....com>
To:     Jeffrey Hugo <quic_jhugo@...cinc.com>, quic_carlv@...cinc.com,
        quic_pkanojiy@...cinc.com, sukrut.bellary@...ux.com,
        sumit.semwal@...aro.org
Cc:     ogabbay@...nel.org, linux-arm-msm@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH] accel/qaic: Call DRM helper function to destroy prime GEM



Am 14.06.23 um 18:15 schrieb Jeffrey Hugo:
> From: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>
>
> smatch warning:
> 	drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
> 		dereferencing freed memory 'obj->import_attach'
>
> obj->import_attach is detached and freed using dma_buf_detach().
> But used after free to decrease the dmabuf ref count using
> dma_buf_put().
>
> drm_prime_gem_destroy() handles this issue and performs the proper clean
> up instead of open coding it in the driver.
>
> Fixes: ff13be830333 ("accel/qaic: Add datapath")
> Reported-by: Sukrut Bellary <sukrut.bellary@...ux.com>
> Closes: https://lore.kernel.org/all/20230610021200.377452-1-sukrut.bellary@linux.com/
> Suggested-by: Christian König <christian.koenig@....com>
> Signed-off-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>
> Reviewed-by: Carl Vanderlip <quic_carlv@...cinc.com>
> Reviewed-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
> Signed-off-by: Jeffrey Hugo <quic_jhugo@...cinc.com>

Reviewed-by: Christian König <christian.koenig@....com>

> ---
>   drivers/accel/qaic/qaic_data.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
> index e42c1f9ffff8..e9a1cb779b30 100644
> --- a/drivers/accel/qaic/qaic_data.c
> +++ b/drivers/accel/qaic/qaic_data.c
> @@ -23,6 +23,7 @@
>   #include <linux/wait.h>
>   #include <drm/drm_file.h>
>   #include <drm/drm_gem.h>
> +#include <drm/drm_prime.h>
>   #include <drm/drm_print.h>
>   #include <uapi/drm/qaic_accel.h>
>   
> @@ -616,8 +617,7 @@ static void qaic_free_object(struct drm_gem_object *obj)
>   
>   	if (obj->import_attach) {
>   		/* DMABUF/PRIME Path */
> -		dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
> -		dma_buf_put(obj->import_attach->dmabuf);
> +		drm_prime_gem_destroy(obj, NULL);
>   	} else {
>   		/* Private buffer allocation path */
>   		qaic_free_sgt(bo->sgt);