Re: [patch] ntb_perf: potential info leak in debugfs

[Dave Jiang <dave.jiang@intel.com>]

On 10/14/2016 12:34 AM, Dan Carpenter wrote:
> This is a static checker warning, not something I'm desperately
> concerned about.  But snprintf() returns the number of bytes that
> would have been copied if there were space.  We really care about the
> number of bytes that actually were copied so we should use scnprintf()
> instead.
> 
> It probably won't overrun, and in that case we may as well just use
> sprintf() but these sorts of things make static checkers and code
> reviewers happier.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>

> 
> diff --git a/drivers/ntb/test/ntb_perf.c b/drivers/ntb/test/ntb_perf.c
> index 6a50f20..2d9ca58 100644
> --- a/drivers/ntb/test/ntb_perf.c
> +++ b/drivers/ntb/test/ntb_perf.c
> @@ -589,7 +589,7 @@ static ssize_t debugfs_run_read(struct file *filp, char __user *ubuf,
>  		return -ENOMEM;
>  
>  	if (mutex_is_locked(&perf->run_mutex)) {
> -		out_off = snprintf(buf, 64, "running\n");
> +		out_off = scnprintf(buf, 64, "running\n");
>  		goto read_from_buf;
>  	}
>  
> @@ -600,14 +600,14 @@ static ssize_t debugfs_run_read(struct file *filp, char __user *ubuf,
>  			break;
>  
>  		if (pctx->status) {
> -			out_off += snprintf(buf + out_off, 1024 - out_off,
> +			out_off += scnprintf(buf + out_off, 1024 - out_off,
>  					    "%d: error %d\n", i,
>  					    pctx->status);
>  			continue;
>  		}
>  
>  		rate = div64_u64(pctx->copied, pctx->diff_us);
> -		out_off += snprintf(buf + out_off, 1024 - out_off,
> +		out_off += scnprintf(buf + out_off, 1024 - out_off,
>  			"%d: copied %llu bytes in %llu usecs, %llu MBytes/s\n",
>  			i, pctx->copied, pctx->diff_us, rate);
>  	}
>