linux-kernel - Re: [PATCH] usb: storage: sddr55: avoid integer overflow

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Message-ID: <Y91zL8OWTUd8iTXt@rowland.harvard.edu>
Date:   Fri, 3 Feb 2023 15:48:47 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Karina Yankevich <k.yankevich@....ru>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, usb-storage@...ts.one-eyed-alien.net,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] usb: storage: sddr55: avoid integer overflow

On Fri, Feb 03, 2023 at 11:18:21PM +0300, Karina Yankevich wrote:
> We're possibly losing information by shifting an int.
> Fix it by adding the necessary cast.

Nonsense.  The card's _total_ capacity is no larger than 128 MB, so a 
page address can't possibly overflow an int.

Alan Stern

> Found by OMP on behalf of Linux Verification Center
> (linuxtesting.org) with SVACE.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Karina Yankevich <k.yankevich@....ru>
> ---
>  drivers/usb/storage/sddr55.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/storage/sddr55.c b/drivers/usb/storage/sddr55.c
> index 15dc25801cdc..4aeff73de147 100644
> --- a/drivers/usb/storage/sddr55.c
> +++ b/drivers/usb/storage/sddr55.c
> @@ -236,7 +236,7 @@ static int sddr55_read_data(struct us_data *us,
>  			memset (buffer, 0, len);
>  		} else {
>  
> -			address = (pba << info->blockshift) + page;
> +			address = ((unsigned long)pba << info->blockshift) + page;
>  
>  			command[0] = 0;
>  			command[1] = LSB_of(address>>16);
> @@ -411,7 +411,7 @@ static int sddr55_write_data(struct us_data *us,
>  			command[4] = 0x40;
>  		}
>  
> -		address = (pba << info->blockshift) + page;
> +		address = ((unsigned long)pba << info->blockshift) + page;
>  
>  		command[1] = LSB_of(address>>16);
>  		command[2] = LSB_of(address>>8); 
> -- 
> 2.39.1
>