Re: [PATCH] netfilter: Use hlist_add_head_rcu() in nf_conntrack_set_hashsize()

[Patrick McHardy <kaber@trash.net>]

Eric Dumazet wrote:
> While working on this stuff, I found one suspect use of hlist_add_head()
> 
> Its not a hot path, I believe following patch would make sure nothing
> wrong happens.
> 
> If a chain contains element A and B, then we might build a new table
> with a new chain containing B and A (in this reverse order), and
> a cpu could see A->next = B (new pointer),  B->next = A (old pointer)

I think you're right.

> [PATCH] netfilter: Use hlist_add_head_rcu() in nf_conntrack_set_hashsize()
> 
> Using hlist_add_head() in nf_conntrack_set_hashsize() is quite dangerous.
> Without any barrier, one CPU could see a loop while doing its lookup.
> Its true new table cannot be seen by another cpu, but previous table is still
> readable.

Applied, thanks Eric.