Messages in this thread | | | Date | Mon, 28 Nov 2022 14:09:19 +0100 | Subject | Re: [PATCH v2] drm/mediatek: Clean dangling pointer on bind error path | From | AngeloGioacchino Del Regno <> |
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Il 25/11/22 17:34, Nícolas F. R. A. Prado ha scritto: > On Wed, Nov 23, 2022 at 10:15:25AM +0100, AngeloGioacchino Del Regno wrote: >> Il 22/11/22 15:39, Nícolas F. R. A. Prado ha scritto: >>> mtk_drm_bind() can fail, in which case drm_dev_put() is called, >>> destroying the drm_device object. However a pointer to it was still >>> being held in the private object, and that pointer would be passed along >>> to DRM in mtk_drm_sys_prepare() if a suspend were triggered at that >>> point, resulting in a panic. Clean the pointer when destroying the >>> object in the error path to prevent this from happening. >>> >>> Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.") >>> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com> >>> >>> --- >>> >>> Changes in v2: >>> - Added Fixes tag >>> >>> drivers/gpu/drm/mediatek/mtk_drm_drv.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c >>> index 39a42dc8fb85..a21ff1b3258c 100644 >>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c >>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c >>> @@ -514,6 +514,7 @@ static int mtk_drm_bind(struct device *dev) >>> err_deinit: >>> mtk_drm_kms_deinit(drm); >>> err_free: >>> + private->drm = NULL; >> >> Sorry for not noticing that in v1, but I've rechecked this function and, while this >> commit does indeed actually solve the described issue, I think it's incomplete. >> >> A few lines before, we have a loop that sets >> >> private->all_drm_private[i]->drm = drm; > > Actually that line only exists with [1] applied, but that commit hasn't been > merged as of yet. I debated whether it would be better to send this fix as is, > or ask Nancy Lin to add the tweaked fix you mention below to that series, but > sending this fix as is seemed better since it can be backported to older kernel > versions. > > So assuming this commit gets merged first, Nancy should make that tweak you > mentioned below to ensure all the pointers are zeroed out, which is why I've > added Nancy to CC. (As a side note, given that only the mmsys with drm_master = > true would ever call the drm suspend helper, even this patch as is is enough to > avoid the panic even with that series applied, still we should zero out all > pointers for good measure) > > [1] https://lore.kernel.org/linux-mediatek/20221107072413.16178-6-nancy.lin@mediatek.com/ >
Sorry about that, you're right - the proposed fix is for the commit you linked, I got confused somehow.
This means that you get my
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cheers!
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