netdev - Re: [PATCH v2] ipv4: synchronize bind() with RTM

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Date:	Thu, 21 Oct 2010 16:10:28 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Timo Teräs <timo.teras@....fi>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] ipv4: synchronize bind() with RTM_NEWADDR
 notifications

Le jeudi 21 octobre 2010 à 16:06 +0300, Timo Teräs a écrit :
> Otherwise we have race condition to user land:
>  1. process A: changes IP address
>  2. process A: kernel sends RTM_NEWADDR (and schedules out)
>  3. process B: gets notification
>  4. process B: tries to bind() to new IP, but fails with EADDRNOTAVAIL
>       because FIB is not yet updated and inet_addr_type() in inet_bind()
>       does not recognize the IP as local
>  5. process A: calls inetaddr_chain notifiers which updates FIB
> 
> Fix the error path to synchronize with configuration changes and retry
> the address type check.
> 
> IPv6 side seems to handle the notifications properly: bind() immediately
> after RTM_NEWADDR succeeds as expected.  This is because ipv6_chk_addr()
> uses inet6_addr_lst which is updated before address notification.
> 
> Signed-off-by: Timo Teräs <timo.teras@....fi>
> ---
> Since there was no reply to my question if this is ok, I interpreted it
> as "maybe". So here's the code for review. Hopefully this helps determining
> if this is an acceptable fix.
> 

Just say : no

Really Timo, this problem must get another fix.

I understand you need an urgent fix, you can use your patch in the
meantime, of course ;)



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