From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] net: compare_ether_addr[_64bits]() has no ordering Date: Mon, 07 May 2012 19:20:52 -0400 (EDT) Message-ID: <20120507.192052.181899101154654170.davem@davemloft.net> References: <1336397946.4325.27.camel@jlt3.sipsolutions.net> <1336398809.3752.2313.camel@edumazet-glaptop> <1336399961.4325.30.camel@jlt3.sipsolutions.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org To: johannes@sipsolutions.net Return-path: Received: from shards.monkeyblade.net ([198.137.202.13]:52341 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755219Ab2EGXV6 (ORCPT ); Mon, 7 May 2012 19:21:58 -0400 In-Reply-To: <1336399961.4325.30.camel@jlt3.sipsolutions.net> Sender: netdev-owner@vger.kernel.org List-ID: From: Johannes Berg Date: Mon, 07 May 2012 16:12:41 +0200 > On Mon, 2012-05-07 at 15:53 +0200, Eric Dumazet wrote: >> On Mon, 2012-05-07 at 15:39 +0200, Johannes Berg wrote: >> > From: Johannes Berg >> > >> > Neither compare_ether_addr() nor compare_ether_addr_64bits() >> > (as it can fall back to the former) have comparison semantics >> > like memcmp() where the sign of the return value indicates sort >> > order. We had a bug in the wireless code due to a blind memcmp >> > replacement because of this. >> > >> > A cursory look suggests that the wireless bug was the only one >> > due to this semantic difference. >> > >> > Signed-off-by: Johannes Berg >> > --- >> > include/linux/etherdevice.h | 11 ++++++----- >> > 1 file changed, 6 insertions(+), 5 deletions(-) >> >> The right way to avoid this kind of problems is to change these >> functions to return a bool > > Well, I guess so, but that'd be a weird thing for a compare_ function... > should probably be named equal_... then, but I'm not really able to do > such a huge change on the first day after my vacation :-) It's true the name could be improved, but changing the name is quite a large undertaking even with automated scripts. Even the bool change is slightly painful, since all of the explicit tests against integers (%99.999 of these are in wireless BTW :-) would need to be adjusted. For now, I'll just apply Johannes's comment fix.