net/sched: act_api: Notify user space if any actions were flushed before error

BugLink: https://bugs.launchpad.net/bugs/1986728
commit 76b39b94382f9e0a639e1c70c3253de248cc4c83 upstream.

If during an action flush operation one of the actions is still being
referenced, the flush operation is aborted and the kernel returns to
user space with an error. However, if the kernel was able to flush, for
example, 3 actions and failed on the fourth, the kernel will not notify
user space that it deleted 3 actions before failing.

This patch fixes that behaviour by notifying user space of how many
actions were deleted before flush failed and by setting extack with a
message describing what happened.

Fixes: 55334a5db5cd ("net_sched: act: refuse to remove bound action outside")
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 7d53272727bfabb1d228a887768745fedf04f9e5..d775676956bf93f4c4ee372d6ecfa36d4b38cac3 100644 (file)
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -350,7 +350,8 @@ static int tcf_idr_release_unsafe(struct tc_action *p)
 }
 
 static int tcf_del_walker(struct tcf_idrinfo *idrinfo, struct sk_buff *skb,
-                         const struct tc_action_ops *ops)
+                         const struct tc_action_ops *ops,
+                         struct netlink_ext_ack *extack)
 {
        struct nlattr *nest;
        int n_i = 0;
@@ -366,20 +367,25 @@ static int tcf_del_walker(struct tcf_idrinfo *idrinfo, struct sk_buff *skb,
        if (nla_put_string(skb, TCA_KIND, ops->kind))
                goto nla_put_failure;
 
+       ret = 0;
        mutex_lock(&idrinfo->lock);
        idr_for_each_entry_ul(idr, p, tmp, id) {
                if (IS_ERR(p))
                        continue;
                ret = tcf_idr_release_unsafe(p);
-               if (ret == ACT_P_DELETED) {
+               if (ret == ACT_P_DELETED)
                        module_put(ops->owner);
-                       n_i++;
-               } else if (ret < 0) {
-                       mutex_unlock(&idrinfo->lock);
-                       goto nla_put_failure;
-               }
+               else if (ret < 0)
+                       break;
+               n_i++;
        }
        mutex_unlock(&idrinfo->lock);
+       if (ret < 0) {
+               if (n_i)
+                       NL_SET_ERR_MSG(extack, "Unable to flush all TC actions");
+               else
+                       goto nla_put_failure;
+       }
 
        ret = nla_put_u32(skb, TCA_FCNT, n_i);
        if (ret)
@@ -400,7 +406,7 @@ int tcf_generic_walker(struct tc_action_net *tn, struct sk_buff *skb,
        struct tcf_idrinfo *idrinfo = tn->idrinfo;
 
        if (type == RTM_DELACTION) {
-               return tcf_del_walker(idrinfo, skb, ops);
+               return tcf_del_walker(idrinfo, skb, ops, extack);
        } else if (type == RTM_GETACTION) {
                return tcf_dump_walker(idrinfo, skb, cb);
        } else {