linux-kernel - Re: [Openipmi-developer] [PATCH][next] ipmi: ipmb: Fix off-by-one size check on rcvlen

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Message-ID: <20211005154031.GD5381@minyard.net>
Date:   Tue, 5 Oct 2021 10:40:31 -0500
From:   Corey Minyard <minyard@....org>
To:     Colin King <colin.king@...onical.com>
Cc:     openipmi-developer@...ts.sourceforge.net,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Openipmi-developer] [PATCH][next] ipmi: ipmb: Fix off-by-one
 size check on rcvlen

On Tue, Oct 05, 2021 at 04:16:11PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> There is an off-by-one bounds check on the rcvlen causing a potential
> out of bounds write on iidev->rcvmsg. Fix this by using the >= operator
> on the bounds check rather than the > operator.

Got it, thanks.

-corey

> 
> Addresses-Coverity: ("Out-of-bounds write")
> Fixes: 0ba0c3c5d1c1 ("ipmi:ipmb: Add initial support for IPMI over IPMB")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/char/ipmi/ipmi_ipmb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/ipmi/ipmi_ipmb.c b/drivers/char/ipmi/ipmi_ipmb.c
> index b10a1fd9c563..77ebec4ed28e 100644
> --- a/drivers/char/ipmi/ipmi_ipmb.c
> +++ b/drivers/char/ipmi/ipmi_ipmb.c
> @@ -192,7 +192,7 @@ static int ipmi_ipmb_slave_cb(struct i2c_client *client,
>  		break;
>  
>  	case I2C_SLAVE_WRITE_RECEIVED:
> -		if (iidev->rcvlen > sizeof(iidev->rcvmsg))
> +		if (iidev->rcvlen >= sizeof(iidev->rcvmsg))
>  			iidev->overrun = true;
>  		else
>  			iidev->rcvmsg[iidev->rcvlen++] = *val;
> -- 
> 2.32.0
> 
> 
> 
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