linux-kernel - Re: [PATCH 01/10] Revert "drm/msm: Add missing check and destroy for alloc_ordered

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Date:   Wed,  8 Mar 2023 10:10:24 +0800
From:   Jiasheng Jiang <jiasheng@...as.ac.cn>
To:     johan+linaro@...nel.org
Cc:     robdclark@...il.com, quic_abhinavk@...cinc.com,
        dmitry.baryshkov@...aro.org, sean@...rly.run, airlied@...il.com,
        daniel@...ll.ch, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Jiasheng Jiang <jiasheng@...as.ac.cn>
Subject: Re: [PATCH 01/10] Revert "drm/msm: Add missing check and destroy for alloc_ordered_workqueue"

On Mon, 06 Mar 2023 18:07:13 +0800, Johan Hovold wrote:
> This reverts commit 643b7d0869cc7f1f7a5ac7ca6bd25d88f54e31d0.

The commit not only adds the allocation sanity check, but also adds the
destroy_workqueue to release the allocated priv->wq.
Therefore, revert the commit will cause memory leak.

> A recent patch that tried to fix up the msm_drm_init() paths with
> respect to the workqueue but only ended up making things worse:
> 
> First, the newly added calls to msm_drm_uninit() on early errors would
> trigger NULL-pointer dereferences, for example, as the kms pointer would
> not have been initialised. (Note that these paths were also modified by
> a second broken error handling patch which in effect cancelled out this
> part when merged.)

There is a check for the kms pointer to avoid NULL-pointer dereference in
the msm_drm_uninit().

> Second, the newly added allocation sanity check would still leak the
> previously allocated drm device.

The ddev is allocated by drm_dev_alloc which support automatic cleanup.

Thanks,
Jiang