linux-kernel - Re: [patch v2] usb: f_fs: off by one bug in _ffs_func

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Message-ID: <xa1t1t4mwkqt.fsf@mina86.com>
Date:	Sat, 28 May 2016 12:16:26 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>,
	Felipe Balbi <balbi@...nel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Robert Baldyga <r.baldyga@...sung.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Daniel Walter <dwalter@...ma-star.at>,
	"Du\, Changbin" <changbin.du@...el.com>,
	Rui Miguel Silva <rui.silva@...aro.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch v2] usb: f_fs: off by one bug in _ffs_func_bind()

On Sat, May 28 2016, Dan Carpenter wrote:
> This loop is supposed to set all the .num[] values to -1 but it's off by
> one so it skips the first element and sets one element past the end of
> the array.
>
> I've cleaned up the loop a little as well.
>
> Fixes: ddf8abd25994 ('USB: f_fs: the FunctionFS driver')
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Acked-by: Michal Nazarewicz <mina86@...a86.com>

> ---
> v2: move the eps_ptr assignment outside the loop.
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 73515d5..d26eb64 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -2729,6 +2729,7 @@ static int _ffs_func_bind(struct usb_configuration *c,
>  		func->ffs->ss_descs_count;
>  
>  	int fs_len, hs_len, ss_len, ret, i;
> +	struct ffs_ep *eps_ptr;
>  
>  	/* Make it a single chunk, less management later on */
>  	vla_group(d);
> @@ -2777,12 +2778,9 @@ static int _ffs_func_bind(struct usb_configuration *c,
>  	       ffs->raw_descs_length);
>  
>  	memset(vla_ptr(vlabuf, d, inums), 0xff, d_inums__sz);
> -	for (ret = ffs->eps_count; ret; --ret) {
> -		struct ffs_ep *ptr;
> -
> -		ptr = vla_ptr(vlabuf, d, eps);
> -		ptr[ret].num = -1;
> -	}
> +	eps_ptr = vla_ptr(vlabuf, d, eps);
> +	for (i = 0; i < ffs->eps_count; i++)
> +		eps_ptr[i].num = -1;
>  
>  	/* Save pointers
>  	 * d_eps == vlabuf, func->eps used to kfree vlabuf later

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»