linux-kernel - Re: [PATCH] tty/n_gsm.c: fix false positive WARN

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Date:	Wed, 25 Nov 2015 19:27:15 +0800
From:	xinhui <xinhui@...ux.vnet.ibm.com>
To:	xinhui <xinhui.pan@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, dvyukov@...gle.com,
	yanmin_zhang@...ux.intel.com
Subject: Re: [PATCH] tty/n_gsm.c: fix false positive WARN_ON and do some codes
 improvement

Hi, Jiri
	I made this patch based on your idea. Any modification is welcome. :)

PS. "xinhui" or "xinhui.pan"@linux.vnet.ibm.com are same mail account, both of them are alias.

thanks
xinhui

On 2015/11/25 19:18, xinhui wrote:
> From: xinhui <xinhui@...ux.vnet.ibm.com>
>
> If gsm driver fails to activate one mux, and this mux is not stored in
> gsm_mux[], there would be a warning in gsm_cleanup_mux(). Actually this
> is a legal case. So just do a simple check instead of WARN_ON.
>
> There is one filed gsm->num to store its index of gsm_mux[]. So use
> gsm->num to remove itself from gsm_mux[] instead of the for-loop
> traverse.
>
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Fixes: 5a64096700dc ("tty/n_gsm.c: fix a memory leak in gsmld_open")
> Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
> ---
>   drivers/tty/n_gsm.c |   12 +++++-------
>   1 files changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index c3fe026..56377e1 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -2037,15 +2037,13 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
>
>   	gsm->dead = 1;
>
> +	/* open failed before registering => nothing to do*/
> +	if (gsm_mux[gsm->num] != gsm)
> +		return;
> +
>   	spin_lock(&gsm_mux_lock);
> -	for (i = 0; i < MAX_MUX; i++) {
> -		if (gsm_mux[i] == gsm) {
> -			gsm_mux[i] = NULL;
> -			break;
> -		}
> -	}
> +	gsm_mux[gsm->num] = NULL;
>   	spin_unlock(&gsm_mux_lock);
> -	WARN_ON(i == MAX_MUX);
>
>   	/* In theory disconnecting DLCI 0 is sufficient but for some
>   	   modems this is apparently not the case. */
>

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