linux-kernel - Re: [PATCH] mtk-sd: Prevent memory corruption from DMA map failure

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Message-Id: <20250625134254.7cbd72feb80d8d050f2f005d@kernel.org>
Date: Wed, 25 Jun 2025 13:42:54 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Ulf Hansson <ulf.hansson@...aro.org>, Chaotian Jing
 <chaotian.jing@...iatek.com>, Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Tomasz Figa <tfiga@...omium.org>, linux-mmc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] mtk-sd: Prevent memory corruption from DMA map failure

On Wed, 25 Jun 2025 13:13:18 +0900
Sergey Senozhatsky <senozhatsky@...omium.org> wrote:

> On (25/06/25 12:56), Sergey Senozhatsky wrote:
> > On (25/06/12 20:26), Masami Hiramatsu (Google) wrote:
> > [..]
> > > @@ -1466,8 +1471,18 @@ static void msdc_ops_request(struct mmc_host *mmc, struct mmc_request *mrq)
> > >  	WARN_ON(!host->hsq_en && host->mrq);
> > >  	host->mrq = mrq;
> > >  
> > > -	if (mrq->data)
> > > +	if (mrq->data) {
> > >  		msdc_prepare_data(host, mrq->data);
> > > +		if (!msdc_data_prepared(mrq->data)) {
> > > +			/*
> > > +			 * Failed to prepare DMA area, fail fast before
> > > +			 * starting any commands.
> > > +			 */
> > > +			mrq->cmd->error = -ENOSPC;
> > > +			mmc_request_done(mmc_from_priv(host), mrq);
> > 
> > Do we end up having a stale/dangling host->mrq pointer here?
> 
> Something like this maybe?

Good catch! I thought it is cleared in mmc_request_done(), but not.
I agree we need to clean it up since it is set in msdc_ops_request().

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks,

> 
> ---
> 
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index b12cfb9a5e5f..46bb770ace41 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -1498,6 +1498,7 @@ static void msdc_ops_request(struct mmc_host *mmc, struct mmc_request *mrq)
>  			 */
>  			mrq->cmd->error = -ENOSPC;
>  			mmc_request_done(mmc_from_priv(host), mrq);
> +			host->mrq = NULL;
>  			return;
>  		}
>  	}


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>