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

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Message-ID: <3e547346-a2ec-b8b2-2d4a-25a75b068e08@osg.samsung.com>
Date:   Thu, 14 Dec 2017 13:14:24 -0700
From:   Shuah Khan <shuahkh@....samsung.com>
To:     Juan Zea <juan.zea@...del.com>, shuah@...nel.org
Cc:     linux-usb@...r.kernel.org,
        Valentina Manea <valentina.manea.m@...il.com>,
        linux-kernel@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH] usbip: fix usbip bind writing random string after command
 in match_busid

On 12/14/2017 03:23 AM, Juan Zea wrote:
>> Why not use the return value from snprintf() for length, instead of calling
> strlen(command)?
> 
> Yes, that makes sense. Something like this?

Yes

> 
> diff --git a/tools/usb/usbip/src/utils.c b/tools/usb/usbip/src/utils.c
> index 2b3d6d2..3d7b42e 100644
> --- a/tools/usb/usbip/src/utils.c
> +++ b/tools/usb/usbip/src/utils.c
> @@ -30,6 +30,7 @@ int modify_match_busid(char *busid, int add)
>         char command[SYSFS_BUS_ID_SIZE + 4];
>         char match_busid_attr_path[SYSFS_PATH_MAX];
>         int rc;
> +       int cmd_size;
>  
>         snprintf(match_busid_attr_path, sizeof(match_busid_attr_path),
>                  "%s/%s/%s/%s/%s/%s", SYSFS_MNT_PATH, SYSFS_BUS_NAME,
> @@ -37,12 +38,14 @@ int modify_match_busid(char *busid, int add)
>                  attr_name);
>  
>         if (add)
> -               snprintf(command, SYSFS_BUS_ID_SIZE + 4, "add %s", busid);
> +               cmd_size = snprintf(command, SYSFS_BUS_ID_SIZE + 4, "add %s",
> +                                   busid);
>         else
> -               snprintf(command, SYSFS_BUS_ID_SIZE + 4, "del %s", busid);
> +               cmd_size = snprintf(command, SYSFS_BUS_ID_SIZE + 4, "del %s",
> +                                   busid);
>  
>         rc = write_sysfs_attribute(match_busid_attr_path, command,
> -                                  sizeof(command));
> +                                  cmd_size);
>         if (rc < 0) {
>                 dbg("failed to write match_busid: %s", strerror(errno));
>                 return -1;
> 
> 
> Regards,
> Juan
> 

thanks,
-- Shuah