linux-kernel - Re: [PATCH] TTY: n_gsm, fix false positive WARN

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Date:	Wed, 25 Nov 2015 10:56:09 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	xinhui <xinhui@...ux.vnet.ibm.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	dvyukov@...gle.com, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...ux.intel.com>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH] TTY: n_gsm, fix false positive WARN_ON

Hi,

On 11/25/2015, 07:32 AM, xinhui wrote:
>     This warning should blame on commit 5a640967 ("tty/n_gsm.c: fix a
> memory leak in gsmld_open()").

Oh, yes, I messed up the "Fixes" line then. It should write:
Fixes: 5a640967 ("tty/n_gsm.c: fix a memory leak in gsmld_open()")

> I have one confusion. As there is field gsm->num to store the index of
> gsm_mux[]. so in gsm_cleanup_mux(), why we still use for-loop to find
> this mux?
> 
> In error handle path, for example, the call trace in this patch, as we
> failed to activate it and the
> gsm->num is invalid(and the value is 0). we can just modify the codes
> like below:
> 
> if(gsm_mux[gsm->num] == gsm)
> ....other work
> else
>     return;
> 
> I think it would work, and the logic is correct. Or I just miss
> something important?

Yup, it looks like a cleanup. Could you prepare a separate patch for that?

Something like this:
        /* open failed before registering => nothing to do */
        if (gsm_mux[gsm->num] != gsm)
              return;
        spin_lock(&gsm_mux_lock);
        gsm_mux[gsm->num] = NULL;
        spin_unlock(&gsm_mux_lock);

thanks,
-- 
js
suse labs
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