netdev - [PATCH net 5/7] net/sched: fix idr leak in the error path of __tcf_ipt

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Message-Id: <c3abf2dd93b945d1cea0e09b040f931660c149ff.1521417146.git.dcaratti@redhat.com>
Date:   Mon, 19 Mar 2018 01:06:15 +0100
From:   Davide Caratti <dcaratti@...hat.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org
Subject: [PATCH net 5/7] net/sched: fix idr leak in the error path of __tcf_ipt_init()

__tcf_ipt_init() can fail after the idr has been successfully reserved.
When this happens, subsequent attempts to configure xt/ipt rules using
the same idr value systematically fail with -ENOSPC:

 # tc action add action xt -j LOG --log-prefix test1 index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "test1" index 100
 RTNETLINK answers: Cannot allocate memory
 We have an error talking to the kernel
 Command "(null)" is unknown, try "tc actions help".
 # tc action add action xt -j LOG --log-prefix test1 index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "test1" index 100
 RTNETLINK answers: No space left on device
 We have an error talking to the kernel
 Command "(null)" is unknown, try "tc actions help".
 # tc action add action xt -j LOG --log-prefix test1 index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "test1" index 100
 RTNETLINK answers: No space left on device
 We have an error talking to the kernel
 ...

Fix this in the error path of __tcf_ipt_init(), calling tcf_idr_release()
in place of tcf_idr_cleanup(). Since tcf_ipt_release() can now be called
when tcfi_t is NULL, we also need to protect calls to ipt_destroy_target()
to avoid NULL pointer dereference.

Fixes: 65a206c01e8e ("net/sched: Change act_api and act_xxx modules to use IDR")
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 net/sched/act_ipt.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c
index 06e380ae0928..71b618144803 100644
--- a/net/sched/act_ipt.c
+++ b/net/sched/act_ipt.c
@@ -80,9 +80,12 @@ static void ipt_destroy_target(struct xt_entry_target *t)
 static void tcf_ipt_release(struct tc_action *a)
 {
 	struct tcf_ipt *ipt = to_ipt(a);
-	ipt_destroy_target(ipt->tcfi_t);
+
+	if (ipt->tfci_t) {
+		ipt_destroy_target(ipt->tcfi_t);
+		kfree(ipt->tcfi_t);
+	}
 	kfree(ipt->tcfi_tname);
-	kfree(ipt->tcfi_t);
 }
 
 static const struct nla_policy ipt_policy[TCA_IPT_MAX + 1] = {
@@ -187,7 +190,7 @@ static int __tcf_ipt_init(struct net *net, unsigned int id, struct nlattr *nla,
 	kfree(tname);
 err1:
 	if (ret == ACT_P_CREATED)
-		tcf_idr_cleanup(*a, est);
+		tcf_idr_release(*a, bind);
 	return err;
 }
 
-- 
2.14.3