6.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 31d7d67ba1274f42494256d52e86da80ed09f3cb ]
rt->fib6_nsiblings can be read locklessly, add corresponding READ_ONCE() and WRITE_ONCE() annotations.
Fixes: 66f5d6ce53e6 ("ipv6: replace rwlock with rcu and spinlock in fib6_table") Signed-off-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20250725140725.3626540-5-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/ip6_fib.c | 20 +++++++++++++------- net/ipv6/route.c | 5 +++-- 2 files changed, 16 insertions(+), 9 deletions(-)
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index c53303e89390..aa1046fbf28e 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -440,15 +440,17 @@ struct fib6_dump_arg { static int fib6_rt_dump(struct fib6_info *rt, struct fib6_dump_arg *arg) { enum fib_event_type fib_event = FIB_EVENT_ENTRY_REPLACE; + unsigned int nsiblings; int err;
if (!rt || rt == arg->net->ipv6.fib6_null_entry) return 0;
- if (rt->fib6_nsiblings) + nsiblings = READ_ONCE(rt->fib6_nsiblings); + if (nsiblings) err = call_fib6_multipath_entry_notifier(arg->nb, fib_event, rt, - rt->fib6_nsiblings, + nsiblings, arg->extack); else err = call_fib6_entry_notifier(arg->nb, fib_event, rt, @@ -1126,7 +1128,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
if (rt6_duplicate_nexthop(iter, rt)) { if (rt->fib6_nsiblings) - rt->fib6_nsiblings = 0; + WRITE_ONCE(rt->fib6_nsiblings, 0); if (!(iter->fib6_flags & RTF_EXPIRES)) return -EEXIST; if (!(rt->fib6_flags & RTF_EXPIRES)) { @@ -1155,7 +1157,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt, */ if (rt_can_ecmp && rt6_qualify_for_ecmp(iter)) - rt->fib6_nsiblings++; + WRITE_ONCE(rt->fib6_nsiblings, + rt->fib6_nsiblings + 1); }
if (iter->fib6_metric > rt->fib6_metric) @@ -1205,7 +1208,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt, fib6_nsiblings = 0; list_for_each_entry_safe(sibling, temp_sibling, &rt->fib6_siblings, fib6_siblings) { - sibling->fib6_nsiblings++; + WRITE_ONCE(sibling->fib6_nsiblings, + sibling->fib6_nsiblings + 1); BUG_ON(sibling->fib6_nsiblings != rt->fib6_nsiblings); fib6_nsiblings++; } @@ -1250,7 +1254,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt, list_for_each_entry_safe(sibling, next_sibling, &rt->fib6_siblings, fib6_siblings) - sibling->fib6_nsiblings--; + WRITE_ONCE(sibling->fib6_nsiblings, + sibling->fib6_nsiblings - 1); WRITE_ONCE(rt->fib6_nsiblings, 0); list_del_rcu(&rt->fib6_siblings); rt6_multipath_rebalance(next_sibling); @@ -1968,7 +1973,8 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn, notify_del = true; list_for_each_entry_safe(sibling, next_sibling, &rt->fib6_siblings, fib6_siblings) - sibling->fib6_nsiblings--; + WRITE_ONCE(sibling->fib6_nsiblings, + sibling->fib6_nsiblings - 1); WRITE_ONCE(rt->fib6_nsiblings, 0); list_del_rcu(&rt->fib6_siblings); rt6_multipath_rebalance(next_sibling); diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 8b84ed926cd1..22866444efc0 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -5240,7 +5240,8 @@ static void ip6_route_mpath_notify(struct fib6_info *rt, */ rcu_read_lock();
- if ((nlflags & NLM_F_APPEND) && rt_last && rt_last->fib6_nsiblings) { + if ((nlflags & NLM_F_APPEND) && rt_last && + READ_ONCE(rt_last->fib6_nsiblings)) { rt = list_first_or_null_rcu(&rt_last->fib6_siblings, struct fib6_info, fib6_siblings); @@ -5773,7 +5774,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb, if (dst->lwtstate && lwtunnel_fill_encap(skb, dst->lwtstate, RTA_ENCAP, RTA_ENCAP_TYPE) < 0) goto nla_put_failure; - } else if (rt->fib6_nsiblings) { + } else if (READ_ONCE(rt->fib6_nsiblings)) { struct fib6_info *sibling; struct nlattr *mp;