From e4feec3174036ba772006be74beee0efa09a9eb8 Mon Sep 17 00:00:00 2001 From: Julian Anastasov Date: Mon, 25 May 2026 07:07:44 +0300 Subject: [PATCH] ipvs: clear the svc scheduler ptr early on edit [ Upstream commit 193989cc6d80dd8e0460fb3992e69fa03bf0ff9b ] ip_vs_edit_service() while unbinding the old scheduler clears the svc->scheduler ptr after the scheduler module initiates RCU callbacks. This can cause packets to use the old scheduler at the time when svc->sched_data is already freed after RCU grace period. Fix it by clearing the ptr early in ip_vs_unbind_scheduler(), before the done_service method schedules any RCU callbacks. Also, if the new scheduler fails to initialize when replacing the old scheduler, try to restore the old scheduler while still returning the error code. Link: https://sashiko.dev/#/patchset/20260519015506.634185-1-rosenp%40gmail.com Fixes: 05f00505a89a ("ipvs: fix crash if scheduler is changed") Signed-off-by: Julian Anastasov Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin --- include/net/ip_vs.h | 3 +-- net/netfilter/ipvs/ip_vs_ctl.c | 13 ++++++++----- net/netfilter/ipvs/ip_vs_sched.c | 14 +++++++------- 3 files changed, 16 insertions(+), 14 deletions(-) diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h index 59f8412de45a..41e20b7e8e88 100644 --- a/include/net/ip_vs.h +++ b/include/net/ip_vs.h @@ -1396,8 +1396,7 @@ int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler); int unregister_ip_vs_scheduler(struct ip_vs_scheduler *scheduler); int ip_vs_bind_scheduler(struct ip_vs_service *svc, struct ip_vs_scheduler *scheduler); -void ip_vs_unbind_scheduler(struct ip_vs_service *svc, - struct ip_vs_scheduler *sched); +void ip_vs_unbind_scheduler(struct ip_vs_service *svc); struct ip_vs_scheduler *ip_vs_scheduler_get(const char *sched_name); void ip_vs_scheduler_put(struct ip_vs_scheduler *scheduler); struct ip_vs_conn * diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c index 4c9ef2ae4d68..0805c9083eaa 100644 --- a/net/netfilter/ipvs/ip_vs_ctl.c +++ b/net/netfilter/ipvs/ip_vs_ctl.c @@ -1417,7 +1417,7 @@ ip_vs_add_service(struct netns_ipvs *ipvs, struct ip_vs_service_user_kern *u, if (ret_hooks >= 0) ip_vs_unregister_hooks(ipvs, u->af); if (svc != NULL) { - ip_vs_unbind_scheduler(svc, sched); + ip_vs_unbind_scheduler(svc); ip_vs_service_free(svc); } ip_vs_scheduler_put(sched); @@ -1479,9 +1479,8 @@ ip_vs_edit_service(struct ip_vs_service *svc, struct ip_vs_service_user_kern *u) old_sched = rcu_dereference_protected(svc->scheduler, 1); if (sched != old_sched) { if (old_sched) { - ip_vs_unbind_scheduler(svc, old_sched); - RCU_INIT_POINTER(svc->scheduler, NULL); - /* Wait all svc->sched_data users */ + ip_vs_unbind_scheduler(svc); + /* Wait all svc->scheduler/sched_data users */ synchronize_rcu(); } /* Bind the new scheduler */ @@ -1489,6 +1488,10 @@ ip_vs_edit_service(struct ip_vs_service *svc, struct ip_vs_service_user_kern *u) ret = ip_vs_bind_scheduler(svc, sched); if (ret) { ip_vs_scheduler_put(sched); + /* Try to restore the old_sched */ + if (old_sched && + !ip_vs_bind_scheduler(svc, old_sched)) + old_sched = NULL; goto out; } } @@ -1545,7 +1548,7 @@ static void __ip_vs_del_service(struct ip_vs_service *svc, bool cleanup) /* Unbind scheduler */ old_sched = rcu_dereference_protected(svc->scheduler, 1); - ip_vs_unbind_scheduler(svc, old_sched); + ip_vs_unbind_scheduler(svc); ip_vs_scheduler_put(old_sched); /* Unbind persistence engine, keep svc->pe */ diff --git a/net/netfilter/ipvs/ip_vs_sched.c b/net/netfilter/ipvs/ip_vs_sched.c index d4903723be7e..49b2e5d2b2c8 100644 --- a/net/netfilter/ipvs/ip_vs_sched.c +++ b/net/netfilter/ipvs/ip_vs_sched.c @@ -57,19 +57,19 @@ int ip_vs_bind_scheduler(struct ip_vs_service *svc, /* * Unbind a service with its scheduler */ -void ip_vs_unbind_scheduler(struct ip_vs_service *svc, - struct ip_vs_scheduler *sched) +void ip_vs_unbind_scheduler(struct ip_vs_service *svc) { - struct ip_vs_scheduler *cur_sched; + struct ip_vs_scheduler *sched; - cur_sched = rcu_dereference_protected(svc->scheduler, 1); - /* This check proves that old 'sched' was installed */ - if (!cur_sched) + sched = rcu_dereference_protected(svc->scheduler, 1); + if (!sched) return; + /* Reset the scheduler before initiating any RCU callbacks */ + rcu_assign_pointer(svc->scheduler, NULL); + smp_wmb(); /* paired with smp_rmb() in ip_vs_schedule() */ if (sched->done_service) sched->done_service(svc); - /* svc->scheduler can be set to NULL only by caller */ }