net/sched: act_ipt: fix refcount leak when replace fails [Linux 5.0]

net/sched: act_ipt: fix refcount leak when replace fails [Linux 5.0]

This Linux kernel change "net/sched: act_ipt: fix refcount leak when replace fails" is included in the Linux 5.0 release. This change is authored by Davide Caratti <dcaratti [at] redhat.com> on Fri Feb 22 12:33:25 2019 +0100. The commit for this change in Linux stable tree is 8f67c90 (patch).

net/sched: act_ipt: fix refcount leak when replace fails

After commit 4e8ddd7f1758 ("net: sched: don't release reference on action
overwrite"), the error path of all actions was converted to drop refcount
also when the action was being overwritten. But we forgot act_ipt_init(),
in case allocation of 'tname' was not successful:

 # tc action add action xt -j LOG --log-prefix hello index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "hello" index 100
 # tc action show action xt
 total acts 1

         action order 0: tablename: mangle  hook: NF_IP_POST_ROUTING
         target  LOG level warning prefix "hello"
         index 100 ref 1 bind 0
 # tc action replace action xt -j LOG --log-prefix world index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "world" index 100
 RTNETLINK answers: Cannot allocate memory
 We have an error talking to the kernel
 # tc action show action xt
 total acts 1

         action order 0: tablename: mangle  hook: NF_IP_POST_ROUTING
         target  LOG level warning prefix "hello"
         index 100 ref 2 bind 0

Ensure we call tcf_idr_release(), in case 'tname' allocation failed, also
when the action is being replaced.

Fixes: 4e8ddd7f1758 ("net: sched: don't release reference on action overwrite")
Signed-off-by: Davide Caratti <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

There are 3 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/sched/act_ipt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c
index 8af6c11..faa1add 100644
--- a/net/sched/act_ipt.c
+++ b/net/sched/act_ipt.c
@@ -199,8 +199,7 @@ static int __tcf_ipt_init(struct net *net, unsigned int id, struct nlattr *nla,
 err2:
    kfree(tname);
 err1:
-   if (ret == ACT_P_CREATED)
-       tcf_idr_release(*a, bind);
+   tcf_idr_release(*a, bind);
    return err;
 }

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