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Subject: Re: [PATCH] net/9p/client.c: put refcount of trans_mod in error case
 in parse_opts()
To:     piaojun <piaojun@huawei.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        <ericvh@gmail.com>, <rminnich@sandia.gov>, <lucho@ionkov.net>
References: <5B3F39A0.2030509@huawei.com>
CC:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        <v9fs-developer@lists.sourceforge.net>
From:   jiangyiwen <jiangyiwen@huawei.com>
Message-ID: <5B3F3AD1.9010101@huawei.com>
Date:   Fri, 6 Jul 2018 17:48:01 +0800
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On 2018/7/6 17:42, piaojun wrote:
>>From my test, the second mount will fail after umounting successfully.
> The reason is that we put refcount of trans_mod in the correct case rather
> than the error case in parse_opts() at last. That will cause the refcount
> decrease to -1, and when we try to get trans_mod again in
> try_module_get(), we could only increase refcount to 0 which will cause
> failure as follows:
> parse_opts
>   v9fs_get_trans_by_name
>     try_module_get : return NULL to caller which cause error
> 
> So we should put refcount of trans_mod in error case.
> 
> Fixes: 9421c3e64137ec ("net/9p/client.c: fix potential refcnt problem of trans module")
> 
> Signed-off-by: Jun Piao <piaojun@huawei.com>

It looks good to me.

Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>

> ---
>  net/9p/client.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 18c5271..5c13431 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -225,7 +225,8 @@ static int parse_opts(char *opts, struct p9_client *clnt)
>  	}
> 
>  free_and_return:
> -	v9fs_put_trans(clnt->trans_mod);
> +	if (ret)
> +		v9fs_put_trans(clnt->trans_mod);
>  	kfree(tmp_options);
>  	return ret;
>  }
>