From: Eric Dumazet <eric.dumazet@gmail.com>
To: Li RongQing <lirongqing@baidu.com>, netdev@vger.kernel.org
Subject: Re: [PATCH][net-next] ipv6: sanitize RCU usage on fib6_next
Date: Fri, 22 Feb 2019 15:08:38 -0800 [thread overview]
Message-ID: <48790843-066f-668b-c840-6ab34fc2fcf4@gmail.com> (raw)
In-Reply-To: <1550828682-10608-1-git-send-email-lirongqing@baidu.com>
On 02/22/2019 01:44 AM, Li RongQing wrote:
> using rcu_assign_pointer when setting, which has a memory
> barrier to ensure the initialization is seen first.
>
> using rcu_dereference when dereference this pointer
>
> Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
> net/ipv6/ip6_fib.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
> index 6613d8dbb0e5..b73d40d68178 100644
> --- a/net/ipv6/ip6_fib.c
> +++ b/net/ipv6/ip6_fib.c
> @@ -1143,7 +1143,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
>
> atomic_inc(&rt->fib6_ref);
> rcu_assign_pointer(rt->fib6_node, fn);
> - rt->fib6_next = iter->fib6_next;
> + rcu_assign_pointer(rt->fib6_next, iter->fib6_next);
We do not need a barrier here, the object is still private.
> rcu_assign_pointer(*ins, rt);
> if (!info->skip_notify)
> inet6_rt_notify(RTM_NEWROUTE, rt, info, NLM_F_REPLACE);
> @@ -1761,7 +1761,9 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
> RT6_TRACE("fib6_del_route\n");
>
> /* Unlink it */
> - *rtp = rt->fib6_next;
> + *rtp = rcu_dereference_protected(rt->fib6_next,
> + lockdep_is_held(&rt->fib6_table->tb6_lock));
This change will likely add a sparse bug.
> +
> rt->fib6_node = NULL;
> net->ipv6.rt6_stats->fib_rt_entries--;
> net->ipv6.rt6_stats->fib_discarded_routes++;
>
Really I do not believe these changes are needed.
barriers should be added blindly.
next prev parent reply other threads:[~2019-02-22 23:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-22 9:44 [PATCH][net-next] ipv6: sanitize RCU usage on fib6_next Li RongQing
2019-02-22 22:35 ` David Ahern
2019-02-22 23:08 ` Eric Dumazet [this message]
2019-02-24 3:19 ` kbuild test robot
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