netdev - Re: [PATCH net-next v1] net/9p/trans_fd: check the return value of parse

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Date:   Thu, 22 Sep 2022 06:23:35 +0900
From:   asmadeus@...ewreck.org
To:     Li Zhong <floridsleeves@...il.com>
Cc:     netdev@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
        pabeni@...hat.com, kuba@...nel.org, edumazet@...gle.com,
        davem@...emloft.net, linux_oss@...debyte.com, lucho@...kov.net,
        ericvh@...il.com
Subject: Re: [PATCH net-next v1] net/9p/trans_fd: check the return value of
 parse_opts

Li Zhong wrote on Wed, Sep 21, 2022 at 02:09:21PM -0700:
> parse_opts() could fail when there is error parsing mount options into
> p9_fd_opts structure due to allocation failure. In that case opts will
> contain invalid data.

In practice opts->rfd/wfd is set to ~0 before the failure modes so they
will contain exactly what we want them to contain: something that'll
fail the check below.

It is however cleared like this so I'll queue this patch in 9p tree when
I have a moment, but I'll clarify the commit message to say this is
NO-OP : please feel free to send a v2 if you want to put your own words
in there; otherwise it'll be something like below:
----
net/9p: clarify trans_fd parse_opt failure handling

This parse_opts will set invalid opts.rfd/wfd in case of failure which
we already check, but it is not clear for readers that parse_opts error
are handled in p9_fd_create: clarify this by explicitely checking the
return value.
----


Also, in practice args != null doesn't seem to be checked before (the
parse_opt() in client.c allows it) so keeping the error message common
might be better?
(allocation failure will print its own messages anyway and doesn't need
checking)

> 
> Signed-off-by: Li Zhong <floridsleeves@...il.com>
> ---
>  net/9p/trans_fd.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
> index e758978b44be..11ae64c1a24b 100644
> --- a/net/9p/trans_fd.c
> +++ b/net/9p/trans_fd.c
> @@ -1061,7 +1061,9 @@ p9_fd_create(struct p9_client *client, const char *addr, char *args)
>  	int err;
>  	struct p9_fd_opts opts;
>  
> -	parse_opts(args, &opts);
> +	err = parse_opts(args, &opts);
> +	if (err < 0)
> +		return err;
>  	client->trans_opts.fd.rfd = opts.rfd;
>  	client->trans_opts.fd.wfd = opts.wfd;
>