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

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Message-ID: <cifhvofebjuanprzcs2duv6r22r5reibzm7nub4xfya3h3rmwe@ujpf5wadwh3c>
Date: Wed, 25 Jun 2025 13:13:18 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>, 
	Ulf Hansson <ulf.hansson@...aro.org>
Cc: 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, Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH] mtk-sd: Prevent memory corruption from DMA map failure

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?

---

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;
 		}
 	}