linux-kernel - Re: [V9fs-developer] [PATCH v2 1/2] net/9p: detecting invalid options as much as possible

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Message-Id: <20180502153258.39b65209a0a85063441c6d85@linux-foundation.org>
Date:   Wed, 2 May 2018 15:32:58 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Chengguang Xu <cgxu519@....com>
Cc:     ericvh@...il.com, rminnich@...dia.gov, lucho@...kov.net,
        v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [V9fs-developer] [PATCH v2 1/2] net/9p: detecting invalid
 options as much as possible

On Tue, 17 Apr 2018 14:45:01 +0800 Chengguang Xu <cgxu519@....com> wrote:

> Currently when detecting invalid options in option parsing,
> some options(e.g. msize) just set errno and allow to continuously
> validate other options so that it can detect invalid options
> as much as possible and give proper error messages together.
> 
> This patch applies same rule to option 'trans' and 'version'
> when detecting EINVAL.
> 
> ...

A few issues:

> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -199,7 +199,7 @@ static int parse_opts(char *opts, struct p9_client *clnt)
>  					s);
>  				ret = -EINVAL;
>  				kfree(s);
> -				goto free_and_return;
> +				continue;
>  			}
>  			kfree(s);
>  			break;

Here we can just do

--- a/net/9p/client.c~net-9p-detecting-invalid-options-as-much-as-possible-fix
+++ a/net/9p/client.c
@@ -198,8 +198,6 @@ static int parse_opts(char *opts, struct
 				pr_info("Could not find request transport: %s\n",
 					s);
 				ret = -EINVAL;
-				kfree(s);
-				continue;
 			}
 			kfree(s);
 			break;

> @@ -217,7 +217,7 @@ static int parse_opts(char *opts, struct p9_client *clnt)
>  			ret = get_protocol_version(s);

And here's the patch introduces a bug: if `ret' has value -EINVAL from
an earlier parsing error, this code will overwrite that error code with
zero.

So you'll need to introduce a new temporary variable here.  And I
suggest that for future-safety, we permit all error returns from
get_protocol_version(), not just -EINVAL.  So something like:

--- a/net/9p/client.c~net-9p-detecting-invalid-options-as-much-as-possible-fix
+++ a/net/9p/client.c
@@ -214,13 +214,12 @@ static int parse_opts(char *opts, struct
 					 "problem allocating copy of version arg\n");
 				goto free_and_return;
 			}
-			ret = get_protocol_version(s);
-			if (ret == -EINVAL) {
-				kfree(s);
-				continue;
-			}
+			pv = get_protocol_version(s);
+			if (pv >= 0)
+				clnt->proto_version = pv;
+			else
+				ret = pv;
 			kfree(s);
-			clnt->proto_version = ret;
 			break;
 		default:
 			continue;
_


Similar changes can be made to patch 2/2.