linux-kernel - Re: [PATCH] usbip: fix usbip bind writing random string after command in match

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Message-ID: <7eb8f072-c4fe-92c9-a7ad-dda390b5f9db@kernel.org>
Date:   Wed, 13 Dec 2017 10:42:44 -0700
From:   Shuah Khan <shuah@...nel.org>
To:     Juan Zea <juan.zea@...del.com>, linux-usb@...r.kernel.org
Cc:     Valentina Manea <valentina.manea.m@...il.com>,
        linux-kernel@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH] usbip: fix usbip bind writing random string after command
 in match_busid

On 12/13/2017 04:07 AM, Juan Zea wrote:
> usbip bind writes commands followed by random string when writing to
> match_busid attribute in sysfs, caused by using full variable size
> instead of string length.
> 
> Signed-off-by: Juan Zea <juan.zea@...del.com>
> ---
>  tools/usb/usbip/src/utils.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/usb/usbip/src/utils.c b/tools/usb/usbip/src/utils.c
> index 2b3d6d2..ea1a1af 100644
> --- a/tools/usb/usbip/src/utils.c
> +++ b/tools/usb/usbip/src/utils.c
> @@ -42,7 +42,7 @@ int modify_match_busid(char *busid, int add)
>                 snprintf(command, SYSFS_BUS_ID_SIZE + 4, "del %s", busid);
>  
>         rc = write_sysfs_attribute(match_busid_attr_path, command,
> -                                  sizeof(command));
> +                                  strlen(command));
>         if (rc < 0) {
>                 dbg("failed to write match_busid: %s", strerror(errno));
>                 return -1;
> 

Why not use the return value from snprintf() for length, instead of calling
strlen(command)?

thanks,
-- Shuah