From 28e6b67f0b292f557468c139085303b15f1a678f Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 29 Jul 2015 23:35:25 +0200 Subject: net: sched: fix refcount imbalance in actions Since commit 55334a5db5cd ("net_sched: act: refuse to remove bound action outside"), we end up with a wrong reference count for a tc action. Test case 1: FOO="1,6 0 0 4294967295," BAR="1,6 0 0 4294967294," tc filter add dev foo parent 1: bpf bytecode "$FOO" flowid 1:1 \ action bpf bytecode "$FOO" tc actions show action bpf action order 0: bpf bytecode '1,6 0 0 4294967295' default-action pipe index 1 ref 1 bind 1 tc actions replace action bpf bytecode "$BAR" index 1 tc actions show action bpf action order 0: bpf bytecode '1,6 0 0 4294967294' default-action pipe index 1 ref 2 bind 1 tc actions replace action bpf bytecode "$FOO" index 1 tc actions show action bpf action order 0: bpf bytecode '1,6 0 0 4294967295' default-action pipe index 1 ref 3 bind 1 Test case 2: FOO="1,6 0 0 4294967295," tc filter add dev foo parent 1: bpf bytecode "$FOO" flowid 1:1 action ok tc actions show action gact action order 0: gact action pass random type none pass val 0 index 1 ref 1 bind 1 tc actions add action drop index 1 RTNETLINK answers: File exists [...] tc actions show action gact action order 0: gact action pass random type none pass val 0 index 1 ref 2 bind 1 tc actions add action drop index 1 RTNETLINK answers: File exists [...] tc actions show action gact action order 0: gact action pass random type none pass val 0 index 1 ref 3 bind 1 What happens is that in tcf_hash_check(), we check tcf_common for a given index and increase tcfc_refcnt and conditionally tcfc_bindcnt when we've found an existing action. Now there are the following cases: 1) We do a late binding of an action. In that case, we leave the tcfc_refcnt/tcfc_bindcnt increased and are done with the ->init() handler. This is correctly handeled. 2) We replace the given action, or we try to add one without replacing and find out that the action at a specific index already exists (thus, we go out with error in that case). In case of 2), we have to undo the reference count increase from tcf_hash_check() in the tcf_hash_check() function. Currently, we fail to do so because of the 'tcfc_bindcnt > 0' check which bails out early with an -EPERM error. Now, while commit 55334a5db5cd prevents 'tc actions del action ...' on an already classifier-bound action to drop the reference count (which could then become negative, wrap around etc), this restriction only accounts for invocations outside a specific action's ->init() handler. One possible solution would be to add a flag thus we possibly trigger the -EPERM ony in situations where it is indeed relevant. After the patch, above test cases have correct reference count again. Fixes: 55334a5db5cd ("net_sched: act: refuse to remove bound action outside") Signed-off-by: Daniel Borkmann Reviewed-by: Cong Wang Signed-off-by: David S. Miller --- include/net/act_api.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'include/net/act_api.h') diff --git a/include/net/act_api.h b/include/net/act_api.h index 3ee4c92afd1b..931738bc5bba 100644 --- a/include/net/act_api.h +++ b/include/net/act_api.h @@ -99,7 +99,6 @@ struct tc_action_ops { int tcf_hash_search(struct tc_action *a, u32 index); void tcf_hash_destroy(struct tc_action *a); -int tcf_hash_release(struct tc_action *a, int bind); u32 tcf_hash_new_index(struct tcf_hashinfo *hinfo); int tcf_hash_check(u32 index, struct tc_action *a, int bind); int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a, @@ -107,6 +106,13 @@ int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a, void tcf_hash_cleanup(struct tc_action *a, struct nlattr *est); void tcf_hash_insert(struct tc_action *a); +int __tcf_hash_release(struct tc_action *a, bool bind, bool strict); + +static inline int tcf_hash_release(struct tc_action *a, bool bind) +{ + return __tcf_hash_release(a, bind, false); +} + int tcf_register_action(struct tc_action_ops *a, unsigned int mask); int tcf_unregister_action(struct tc_action_ops *a); int tcf_action_destroy(struct list_head *actions, int bind); -- cgit v1.2.3-58-ga151