From 93e71edfd90ca7e07a3645167f1e8e4504d4e8ee Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Tue, 10 Jan 2023 20:29:08 -0800 Subject: [PATCH] devlink: keep the instance mutex alive until references are gone The reference needs to keep the instance memory around, but also the instance lock must remain valid. Users will take the lock, check registration status and release the lock. mutex_destroy() etc. belong in the same place as the freeing of the memory. Unfortunately lockdep_unregister_key() sleeps so we need to switch the an rcu_work. Note that the problem is a bit hard to repro, because devlink_pernet_pre_exit() iterates over registered instances. AFAIU the instances must get devlink_free()d concurrently with the namespace getting deleted for the problem to occur. Reported-by: syzbot+d94d214ea473e218fc89@syzkaller.appspotmail.com Reported-by: syzbot+9f0dd863b87113935acf@syzkaller.appspotmail.com Fixes: 9053637e0da7 ("devlink: remove the registration guarantee of references") Reviewed-by: Jiri Pirko Reviewed-by: Jacob Keller Link: https://lore.kernel.org/r/20230111042908.988199-1-kuba@kernel.org Signed-off-by: Jakub Kicinski --- net/devlink/core.c | 16 +++++++++++++--- net/devlink/devl_internal.h | 3 ++- 2 files changed, 15 insertions(+), 4 deletions(-) diff --git a/net/devlink/core.c b/net/devlink/core.c index a31a317626d75..60beca2df7ccb 100644 --- a/net/devlink/core.c +++ b/net/devlink/core.c @@ -83,10 +83,21 @@ struct devlink *__must_check devlink_try_get(struct devlink *devlink) return NULL; } +static void devlink_release(struct work_struct *work) +{ + struct devlink *devlink; + + devlink = container_of(to_rcu_work(work), struct devlink, rwork); + + mutex_destroy(&devlink->lock); + lockdep_unregister_key(&devlink->lock_key); + kfree(devlink); +} + void devlink_put(struct devlink *devlink) { if (refcount_dec_and_test(&devlink->refcount)) - kfree_rcu(devlink, rcu); + queue_rcu_work(system_wq, &devlink->rwork); } struct devlink *devlinks_xa_find_get(struct net *net, unsigned long *indexp) @@ -231,6 +242,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops, INIT_LIST_HEAD(&devlink->trap_list); INIT_LIST_HEAD(&devlink->trap_group_list); INIT_LIST_HEAD(&devlink->trap_policer_list); + INIT_RCU_WORK(&devlink->rwork, devlink_release); lockdep_register_key(&devlink->lock_key); mutex_init(&devlink->lock); lockdep_set_class(&devlink->lock, &devlink->lock_key); @@ -259,8 +271,6 @@ void devlink_free(struct devlink *devlink) mutex_destroy(&devlink->linecards_lock); mutex_destroy(&devlink->reporters_lock); - mutex_destroy(&devlink->lock); - lockdep_unregister_key(&devlink->lock_key); WARN_ON(!list_empty(&devlink->trap_policer_list)); WARN_ON(!list_empty(&devlink->trap_group_list)); WARN_ON(!list_empty(&devlink->trap_list)); diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h index 5d2bbe2956596..e724e4c2a4ffd 100644 --- a/net/devlink/devl_internal.h +++ b/net/devlink/devl_internal.h @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -51,7 +52,7 @@ struct devlink { struct lock_class_key lock_key; u8 reload_failed:1; refcount_t refcount; - struct rcu_head rcu; + struct rcu_work rwork; struct notifier_block netdevice_nb; char priv[] __aligned(NETDEV_ALIGN); };