netdev - Re: [PATCH] net: compare_ether_addr[

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Date:	Mon, 07 May 2012 16:12:41 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: compare_ether_addr[_64bits]() has no ordering

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 <johannes.berg@...el.com>
> > 
> > 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 <johannes.berg@...el.com>
> > ---
> >  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 :-)

johannes

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