linux-kernel - Re: [PATCH V3] MMC: core: cap MMC card timeouts at UINT

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Date:	Mon, 04 Jun 2012 11:13:08 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	"Torne (Richard Coles)" <torne@...gle.com>
CC:	cjb@...top.org, linus.walleij@...aro.org, jh80.chung@...sung.com,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	ben@...adent.org.uk
Subject: Re: [PATCH V3] MMC: core: cap MMC card timeouts at UINT_MAX

On 01/06/12 16:20, Torne (Richard Coles) wrote:
> From: "Torne (Richard Coles)" <torne@...gle.com>
> 
> MMC CSD info can specify very large, ridiculous timeouts, big enough to
> overflow timeout_ns. This can result in the card timing out on every
> operation because the wrapped timeout value is far too small.
> 
> Fix the overflow by capping the result at UINT_MAX.  Cards specifying
> longer timeouts are almost certainly insane, and host controllers
> generally cannot support timeouts that long in any case.
> 
> Signed-off-by: Torne (Richard Coles) <torne@...gle.com>
> ---
>  drivers/mmc/core/core.c |   11 ++++++++++-
>  1 files changed, 10 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 0b6141d..74ec3d4 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -512,7 +512,16 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card)
>  	if (data->flags & MMC_DATA_WRITE)
>  		mult <<= card->csd.r2w_factor;
>  
> -	data->timeout_ns = card->csd.tacc_ns * mult;
> +	/*
> +	 * The timeout in nanoseconds may overflow with some cards. Cap it at
> +	 * UINT_MAX to avoid the overflow; host controllers cannot generally
> +	 * generate timeouts that long anyway.
> +	 */
> +	if (card->csd.tacc_ns <= UINT_MAX / mult)
> +		data->timeout_ns = card->csd.tacc_ns * mult;
> +	else
> +		data->timeout_ns = UINT_MAX;
> +
>  	data->timeout_clks = card->csd.tacc_clks * mult;
>  
>  	/*

Acked-by: Adrian Hunter <adrian.hunter@...el.com>
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