On Sun, Jul 13, 2014 at 3:01 PM, Christoph Schulz <develop@xxxxxxxxxx> wrote:
> From: Christoph Schulz <develop@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Thank you for fixing it.
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