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

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Message-ID: <kgxqtfdrlc5m5kgprjajt4xtngken2u2locauzhsxm7kcowusa@44ncy4vhy5vx>
Date: Wed, 25 Jun 2025 12:56:37 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Chaotian Jing <chaotian.jing@...iatek.com>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Tomasz Figa <tfiga@...omium.org>, 
	Sergey Senozhatsky <senozhatsky@...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 (25/06/12 20:26), Masami Hiramatsu (Google) wrote:
[..]
> +static bool msdc_data_prepared(struct mmc_data *data)
> +{
> +	return data->host_cookie & MSDC_PREPARE_FLAG;
> +}
> +
>  static void msdc_unprepare_data(struct msdc_host *host, struct mmc_data *data)
>  {
>  	if (data->host_cookie & MSDC_ASYNC_FLAG)
> @@ -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?

> +			return;
> +		}
> +	}
>  
>  	/* if SBC is required, we have HW option and SW option.
>  	 * if HW option is enabled, and SBC does not have "special" flags,
>