From: Patrick McHardy <kaber@trash•net>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: David Miller <davem@davemloft•net>,
netdev@vger•kernel.org, paulmck@linux•vnet.ibm.com
Subject: Re: [PATCH] net: nf_conntrack_alloc() fixes
Date: Thu, 16 Jul 2009 14:05:02 +0200 [thread overview]
Message-ID: <4A5F176E.7010508@trash.net> (raw)
In-Reply-To: <4A5E33D9.2030602@gmail.com>
Eric Dumazet wrote:
> [PATCH] net: nf_conntrack_alloc() fixes
>
> When a slab cache uses SLAB_DESTROY_BY_RCU, we must be careful when allocating
> objects, since slab allocator could give a freed object still used by lockless
> readers.
>
> In particular, nf_conntrack RCU lookups rely on ct->tuplehash[xxx].hnnode.next
> being always valid (ie containing a valid 'nulls' value, or a valid pointer to next
> object in hash chain.)
>
> kmem_cache_zalloc() setups object with NULL values, but a NULL value is not valid
> for ct->tuplehash[xxx].hnnode.next.
>
> Fix is to call kmem_cache_alloc() and do the zeroing ourself.
>
> As spotted by Patrick, we also need to make sure lookup keys are committed to
> memory before setting refcount to 1, or a lockless reader could get a reference
> on the old version of the object. Its key re-check could then pass the barrier.
Looks good to me. Applied, thanks Eric. I'll push it to -stable
with the other fixes in a couple of days.
next prev parent reply other threads:[~2009-07-16 12:05 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-01 18:08 WARNING: at include/net/sock.h:417 udp_lib_unhash Tantilov, Emil S
2009-07-02 6:10 ` Eric Dumazet
2009-07-07 0:54 ` Emil S Tantilov
2009-07-07 7:21 ` Eric Dumazet
2009-07-07 7:40 ` Eric Dumazet
2009-07-07 16:14 ` [PATCH] net: sk_alloc() should not blindly overwrite memory Eric Dumazet
2009-07-07 18:33 ` Tantilov, Emil S
2009-07-07 22:33 ` [PATCH] net: sk_prot_alloc() " Eric Dumazet
2009-07-08 2:14 ` David Miller
2009-07-08 6:50 ` Eric Dumazet
2009-07-09 5:36 ` Eric Dumazet
2009-07-09 17:13 ` Paul E. McKenney
2009-07-09 20:50 ` Eric Dumazet
2009-07-12 3:27 ` David Miller
2009-07-12 7:07 ` Eric Dumazet
2009-07-15 12:28 ` [PATCH] net: nf_conntrack_alloc() should not use kmem_cache_zalloc() Eric Dumazet
2009-07-15 15:28 ` Patrick McHardy
2009-07-15 19:54 ` [PATCH] net: nf_conntrack_alloc() fixes Eric Dumazet
2009-07-16 9:13 ` [PATCH] net: sock_copy() fixes Eric Dumazet
2009-07-17 1:09 ` David Miller
2009-07-16 12:05 ` Patrick McHardy [this message]
2009-07-08 17:02 ` [PATCH] net: sk_prot_alloc() should not blindly overwrite memory Tantilov, Emil S
2009-07-08 17:45 ` David Miller
2009-07-08 23:21 ` Eric Dumazet
2009-07-08 23:35 ` Tantilov, Emil S
2009-07-09 0:20 ` [PATCH] net: ip_push_pending_frames() fix Eric Dumazet
2009-07-09 14:32 ` Tantilov, Emil S
2009-07-09 14:38 ` Eric Dumazet
2009-07-12 3:27 ` David Miller
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