linux-kernel - Re: [QUESTION] drm/crtc: precondition for drm_crtc_init_with

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Message-ID: <u366i76e3qhh3ra5oxrtngjtm2u5lterkekcz6y2jkndhuxzli@diujon4h7qwb>
Date:   Fri, 25 Aug 2023 13:03:27 +0200
From:   Maxime Ripard <mripard@...nel.org>
To:     e.orlova@...ras.ru
Cc:     p.zabel@...gutronix.de, maarten.lankhorst@...ux.intel.com,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        sumit.semwal@...aro.org, christian.koenig@....com,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        lvc-project@...uxtesting.org
Subject: Re: [QUESTION] drm/crtc: precondition for drm_crtc_init_with_planes()

On Fri, Aug 25, 2023 at 01:18:46PM +0300, e.orlova@...ras.ru wrote:
> Documentation for drm_crtc_init_with_planes() in
> drivers/gpu/drm/drm_crtc.c states: «The crtc structure should not be
> allocated with devm_kzalloc()».
> 
> However, in drivers/gpu/drm/stm/ltdc.c
> the 2nd argument of the function drm_crtc_init_with_planes()
> is a structure allocated with devm_kzalloc()
> 
> Also, in
> drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c
> drivers/gpu/drm/logicvc/logicvc_crtc.c
> drivers/gpu/drm/meson/meson_crtc.c
> drivers/gpu/drm/mxsfb/lcdif_kms.c
> drivers/gpu/drm/mxsfb/mxsfb_kms.c
> drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
> drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> drivers/gpu/drm/sun4i/sun4i_crtc.c
> drivers/gpu/drm/tegra/dc.c
> drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> the 2nd argument of the function drm_crtc_init_with_planes()
> is a field of the structure allocated with devm_kzalloc()
> 
> Is it correct or can it lead to any problems?

It can lead to use-after-free issues, that's why there's that comment :)

Maxime

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