netdev - Re: [PATCH net v2 1/1] net: ppp: don't call sk_chk

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Message-Id: <20140714.161523.399591287185710608.davem@davemloft.net>
Date:	Mon, 14 Jul 2014 16:15:23 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	develop@...stov.de
Cc:	netdev@...r.kernel.org, linux-ppp@...r.kernel.org,
	paulus@...ba.org, isdn@...ux-pingi.de
Subject: Re: [PATCH net v2 1/1] net: ppp: don't call sk_chk_filter twice

From: Christoph Schulz <develop@...stov.de>
Date: Mon, 14 Jul 2014 08:01:10 +0200

> From: Christoph Schulz <develop@...stov.de>
> 
> Commit 568f194e8bd16c353ad50f9ab95d98b20578a39d ("net: ppp: use
> sk_unattached_filter api") causes sk_chk_filter() to be called twice when
> setting a PPP pass or active filter. This applies to both the generic PPP
> subsystem implemented by drivers/net/ppp/ppp_generic.c and the ISDN PPP
> subsystem implemented by drivers/isdn/i4l/isdn_ppp.c. The first call is from
> within get_filter(). The second one is through the call chain
> 
>   ppp_ioctl() or isdn_ppp_ioctl()
>   --> sk_unattached_filter_create()
>       --> __sk_prepare_filter()
>           --> sk_chk_filter()
> 
> The first call from within get_filter() should be deleted as get_filter() is
> called just before calling sk_unattached_filter_create() later on, which
> eventually calls sk_chk_filter() anyway.
> 
> For 3.15.x, this proposed change is a bugfix rather than a pure optimization as
> in that branch, sk_chk_filter() may replace filter codes by other codes which
> are not recognized when executing sk_chk_filter() a second time. So with
> 3.15.x, if sk_chk_filter() is called twice, the second invocation may yield
> EINVAL (this depends on the filter codes found in the filter to be set, but
> because the replacement is done for frequently used codes, this is almost
> always the case). The net effect is that setting pass and/or active PPP filters
> does not work anymore, since sk_unattached_filter_create() always returns
> EINVAL due to the second call to sk_chk_filter(), regardless whether the filter
> was originally sane or not.
> 
> Signed-off-by: Christoph Schulz <develop@...stov.de>

Applied, thank you.
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