netdev - Re: [PATCH net-next] net: add real socket cookies

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 11 Mar 2015 18:31:42 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, salo@...gle.com
Subject: Re: [PATCH net-next] net: add real socket cookies

On Wed, 2015-03-11 at 21:21 -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Wed, 11 Mar 2015 15:30:35 -0700
> 
> > Note that sk_clone_lock() really does the clear for us :
> > 
> > net/core/sock.c:1541:		atomic64_set(&newsk->sk_cookie, 0);
> > 
> > atomic_cmpxchg() is needed here in case a concurrent dumper already
> > caught the new socket.
> 
> How is newsk visible at this moment?
> 
> It is freshly allocated, and not present in any tables.  Nothing even
> indirectly links to it at this point.
> 
> Visibility only happens after we return from this function, in
> routines such as tcp_v4_syn_recv_sock() which do the hash table
> insertion.

Yes, but remember we use RCU with SLAB_DESTROY_BY_RCU thing,
and inet_diag_dump_one_icsk() uses RCU as well.

I wanted to be extra careful here. Note that with v2, this
atomic_cmpxchg() wont happen unless one dump operation previously
revealed the SYN_RECV to the world.

I have no strong opinion and definitely it is currently safe to use
atomic64_set() here.


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html