From: David Ahern <dsahern@gmail.com>
To: Omid Ehtemam-Haghighi <omid.ehtemamhaghighi@menlosecurity.com>,
netdev@vger.kernel.org
Cc: adrian.oliver@menlosecurity.com, Ido Schimmel <idosch@nvidia.com>,
Nicolas Dichtel <nicolas.dichtel@6wind.com>
Subject: Re: [PATCH] net/ipv6: Fix kernel soft lockup in fib6_select_path under high next hop churn
Date: Wed, 15 May 2024 13:26:38 -0600 [thread overview]
Message-ID: <a21b8fb8-6615-47a2-89a4-4ba97922bd46@gmail.com> (raw)
In-Reply-To: <20240514040757.1957761-1-omid.ehtemamhaghighi@menlosecurity.com>
On 5/13/24 10:07 PM, Omid Ehtemam-Haghighi wrote:
> diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
> index c1f62352a481..b4f3627dd045 100644
> --- a/net/ipv6/ip6_fib.c
> +++ b/net/ipv6/ip6_fib.c
> @@ -1037,7 +1037,7 @@ static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn,
> fib6_drop_pcpu_from(rt, table);
>
> if (rt->nh && !list_empty(&rt->nh_list))
> - list_del_init(&rt->nh_list);
> + list_del_rcu(&rt->nh_list);
This path is only for the separate nexthop objects (the rt->nh check),
while you seem to be dependent on the legacy IPv6 multipath code.
>
> if (refcount_read(&rt->fib6_ref) != 1) {
> /* This route is used as dummy address holder in some split
> @@ -1247,7 +1247,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
> fib6_siblings)
> sibling->fib6_nsiblings--;
> rt->fib6_nsiblings = 0;
> - list_del_init(&rt->fib6_siblings);
> + list_del_rcu(&rt->fib6_siblings);
If using rcu for fib6_siblings fixes your problem, then all references
should be updated to annotate or use the rcu apis.
> rt6_multipath_rebalance(next_sibling);
> return err;
> }
> @@ -1965,7 +1965,7 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
> &rt->fib6_siblings, fib6_siblings)
> sibling->fib6_nsiblings--;
> rt->fib6_nsiblings = 0;
> - list_del_init(&rt->fib6_siblings);
> + list_del_rcu(&rt->fib6_siblings);
> rt6_multipath_rebalance(next_sibling);
> }
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 1f4b935a0e57..485a14098958 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -414,7 +414,7 @@ void fib6_select_path(const struct net *net, struct fib6_result *res,
> struct flowi6 *fl6, int oif, bool have_oif_match,
> const struct sk_buff *skb, int strict)
> {
> - struct fib6_info *sibling, *next_sibling;
> + struct fib6_info *sibling;
> struct fib6_info *match = res->f6i;
>
> if (!match->nh && (!match->fib6_nsiblings || have_oif_match))
> @@ -441,8 +441,8 @@ void fib6_select_path(const struct net *net, struct fib6_result *res,
> if (fl6->mp_hash <= atomic_read(&match->fib6_nh->fib_nh_upper_bound))
> goto out;
>
> - list_for_each_entry_safe(sibling, next_sibling, &match->fib6_siblings,
> - fib6_siblings) {
> + list_for_each_entry_rcu(sibling, &match->fib6_siblings,
> + fib6_siblings) {
> const struct fib6_nh *nh = sibling->fib6_nh;
> int nh_upper_bound;
>
prev parent reply other threads:[~2024-05-15 19:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-14 4:07 [PATCH] net/ipv6: Fix kernel soft lockup in fib6_select_path under high next hop churn Omid Ehtemam-Haghighi
2024-05-15 19:26 ` David Ahern [this message]
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