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

This Linux kernel change "net/sched: act_skbedit: 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 12:33:26 2019 +0100. The commit for this change in Linux stable tree is 6191da9 (patch).

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

when act_skbedit was converted to use RCU in the data plane, we added an
error path, but we forgot to drop the action refcount in case of failure
during a 'replace' operation:

 # tc actions add action skbedit ptype otherhost pass index 100
 # tc action show action skbedit
 total acts 1

         action order 0: skbedit  ptype otherhost pass
          index 100 ref 1 bind 0
 # tc actions replace action skbedit ptype otherhost drop index 100
 RTNETLINK answers: Cannot allocate memory
 We have an error talking to the kernel
 # tc action show action skbedit
 total acts 1

         action order 0: skbedit  ptype otherhost pass
          index 100 ref 2 bind 0

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

Fixes: c749cdda9089 ("net/sched: act_skbedit: don't use spinlock in the data path")
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_skbedit.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/sched/act_skbedit.c b/net/sched/act_skbedit.c
index 64dba37..cfceed2 100644
--- a/net/sched/act_skbedit.c
+++ b/net/sched/act_skbedit.c
@@ -189,8 +189,7 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,

    params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
    if (unlikely(!params_new)) {
-       if (ret == ACT_P_CREATED)
-           tcf_idr_release(*a, bind);
+       tcf_idr_release(*a, bind);
        return -ENOMEM;
    }

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