From 87c750e8c38bce706eb32e4d8f1e3402f2cebbd4 Mon Sep 17 00:00:00 2001 From: Vlad Buslov Date: Wed, 7 Apr 2021 18:36:03 +0300 Subject: net: sched: fix action overwrite reference counting Action init code increments reference counter when it changes an action. This is the desired behavior for cls API which needs to obtain action reference for every classifier that points to action. However, act API just needs to change the action and releases the reference before returning. This sequence breaks when the requested action doesn't exist, which causes act API init code to create new action with specified index, but action is still released before returning and is deleted (unless it was referenced concurrently by cls API). Reproduction: $ sudo tc actions ls action gact $ sudo tc actions change action gact drop index 1 $ sudo tc actions ls action gact Extend tcf_action_init() to accept 'init_res' array and initialize it with action->ops->init() result. In tcf_action_add() remove pointers to created actions from actions array before passing it to tcf_action_put_many(). Fixes: cae422f379f3 ("net: sched: use reference counting action init") Reported-by: Kumar Kartikeya Dwivedi Signed-off-by: Vlad Buslov Signed-off-by: David S. Miller --- include/net/act_api.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/net/act_api.h b/include/net/act_api.h index 2bf3092ae7ec..312f0f6554a0 100644 --- a/include/net/act_api.h +++ b/include/net/act_api.h @@ -185,7 +185,7 @@ int tcf_action_exec(struct sk_buff *skb, struct tc_action **actions, int nr_actions, struct tcf_result *res); int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla, struct nlattr *est, char *name, int ovr, int bind, - struct tc_action *actions[], size_t *attr_size, + struct tc_action *actions[], int init_res[], size_t *attr_size, bool rtnl_held, struct netlink_ext_ack *extack); struct tc_action_ops *tc_action_load_ops(char *name, struct nlattr *nla, bool rtnl_held, @@ -193,7 +193,8 @@ struct tc_action_ops *tc_action_load_ops(char *name, struct nlattr *nla, struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp, struct nlattr *nla, struct nlattr *est, char *name, int ovr, int bind, - struct tc_action_ops *ops, bool rtnl_held, + struct tc_action_ops *a_o, int *init_res, + bool rtnl_held, struct netlink_ext_ack *extack); int tcf_action_dump(struct sk_buff *skb, struct tc_action *actions[], int bind, int ref, bool terse); -- cgit v1.2.3 From b3650bf76a32380d4d80a3e21b5583e7303f216c Mon Sep 17 00:00:00 2001 From: Vlad Buslov Date: Wed, 7 Apr 2021 18:36:04 +0300 Subject: net: sched: fix err handler in tcf_action_init() With recent changes that separated action module load from action initialization tcf_action_init() function error handling code was modified to manually release the loaded modules if loading/initialization of any further action in same batch failed. For the case when all modules successfully loaded and some of the actions were initialized before one of them failed in init handler. In this case for all previous actions the module will be released twice by the error handler: First time by the loop that manually calls module_put() for all ops, and second time by the action destroy code that puts the module after destroying the action. Reproduction: $ sudo tc actions add action simple sdata \"2\" index 2 $ sudo tc actions add action simple sdata \"1\" index 1 \ action simple sdata \"2\" index 2 RTNETLINK answers: File exists We have an error talking to the kernel $ sudo tc actions ls action simple total acts 1 action order 0: Simple <"2"> index 2 ref 1 bind 0 $ sudo tc actions flush action simple $ sudo tc actions ls action simple $ sudo tc actions add action simple sdata \"2\" index 2 Error: Failed to load TC action module. We have an error talking to the kernel $ lsmod | grep simple act_simple 20480 -1 Fix the issue by modifying module reference counting handling in action initialization code: - Get module reference in tcf_idr_create() and put it in tcf_idr_release() instead of taking over the reference held by the caller. - Modify users of tcf_action_init_1() to always release the module reference which they obtain before calling init function instead of assuming that created action takes over the reference. - Finally, modify tcf_action_init_1() to not release the module reference when overwriting existing action as this is no longer necessary since both upper and lower layers obtain and manage their own module references independently. Fixes: d349f9976868 ("net_sched: fix RTNL deadlock again caused by request_module()") Suggested-by: Cong Wang Signed-off-by: Vlad Buslov Signed-off-by: David S. Miller --- include/net/act_api.h | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'include') diff --git a/include/net/act_api.h b/include/net/act_api.h index 312f0f6554a0..086b291e9530 100644 --- a/include/net/act_api.h +++ b/include/net/act_api.h @@ -170,12 +170,7 @@ void tcf_idr_insert_many(struct tc_action *actions[]); void tcf_idr_cleanup(struct tc_action_net *tn, u32 index); int tcf_idr_check_alloc(struct tc_action_net *tn, u32 *index, struct tc_action **a, int bind); -int __tcf_idr_release(struct tc_action *a, bool bind, bool strict); - -static inline int tcf_idr_release(struct tc_action *a, bool bind) -{ - return __tcf_idr_release(a, bind, false); -} +int tcf_idr_release(struct tc_action *a, bool bind); int tcf_register_action(struct tc_action_ops *a, struct pernet_operations *ops); int tcf_unregister_action(struct tc_action_ops *a, -- cgit v1.2.3