linux-kernel - Re: [PATCH] staging: lustre: add error handling for try_module

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Message-ID: <87y3fkinht.fsf@notabene.neil.brown.name>
Date:   Tue, 12 Jun 2018 15:26:38 +1000
From:   NeilBrown <neilb@...e.com>
To:     Zhouyang Jia <jiazhouyang09@...il.com>
Cc:     Zhouyang Jia <jiazhouyang09@...il.com>,
        Oleg Drokin <oleg.drokin@...el.com>,
        Andreas Dilger <andreas.dilger@...el.com>,
        James Simmons <jsimmons@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        lustre-devel@...ts.lustre.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: lustre: add error handling for try_module_get

On Tue, Jun 12 2018, Zhouyang Jia wrote:

> When try_module_get fails, the lack of error-handling code may
> cause unexpected results.
>
> This patch adds error-handling code after calling try_module_get.
>
> Signed-off-by: Zhouyang Jia <jiazhouyang09@...il.com>
> ---
>  drivers/staging/lustre/lnet/klnds/socklnd/socklnd.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/staging/lustre/lnet/klnds/socklnd/socklnd.c b/drivers/staging/lustre/lnet/klnds/socklnd/socklnd.c
> index 7086678..72a42bd 100644
> --- a/drivers/staging/lustre/lnet/klnds/socklnd/socklnd.c
> +++ b/drivers/staging/lustre/lnet/klnds/socklnd/socklnd.c
> @@ -2422,7 +2422,10 @@ ksocknal_base_startup(void)
>  
>  	/* flag lists/ptrs/locks initialised */
>  	ksocknal_data.ksnd_init = SOCKNAL_INIT_DATA;
> -	try_module_get(THIS_MODULE);
> +	if (!try_module_get(THIS_MODULE)) {
> +		CERROR("%s: cannot get module\n", __func__);
> +		goto failed;
> +	}
>  
>  	ksocknal_data.ksnd_sched_info = cfs_percpt_alloc(lnet_cpt_table(),
>  							 sizeof(*info));

Thanks for the patch....
I agree that this is probably a bug, but the code is still buggy after
you patch, just in a different way.
Try following through the code and see what happens when you 'goto
failed'.

NeilBrown



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