linux-kernel - [PATCH 3.12 036/142] net sched actions: decrement module reference count after table flush.

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Message-Id: <8463a2e48f91093aeab18c246b60f775ed4a3f1f.1491838390.git.jslaby@suse.cz>
Date:   Mon, 10 Apr 2017 17:31:57 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Roman Mashak <mrv@...atatu.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 036/142] net sched actions: decrement module reference count after table flush.

From: Roman Mashak <mrv@...atatu.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit edb9d1bff4bbe19b8ae0e71b1f38732591a9eeb2 ]

When tc actions are loaded as a module and no actions have been installed,
flushing them would result in actions removed from the memory, but modules
reference count not being decremented, so that the modules would not be
unloaded.

Following is example with GACT action:

% sudo modprobe act_gact
% lsmod
Module                  Size  Used by
act_gact               16384  0
%
% sudo tc actions ls action gact
%
% sudo tc actions flush action gact
% lsmod
Module                  Size  Used by
act_gact               16384  1
% sudo tc actions flush action gact
% lsmod
Module                  Size  Used by
act_gact               16384  2
% sudo rmmod act_gact
rmmod: ERROR: Module act_gact is in use
....

After the fix:
% lsmod
Module                  Size  Used by
act_gact               16384  0
%
% sudo tc actions add action pass index 1
% sudo tc actions add action pass index 2
% sudo tc actions add action pass index 3
% lsmod
Module                  Size  Used by
act_gact               16384  3
%
% sudo tc actions flush action gact
% lsmod
Module                  Size  Used by
act_gact               16384  0
%
% sudo tc actions flush action gact
% lsmod
Module                  Size  Used by
act_gact               16384  0
% sudo rmmod act_gact
% lsmod
Module                  Size  Used by
%

Fixes: f97017cdefef ("net-sched: Fix actions flushing")
Signed-off-by: Roman Mashak <mrv@...atatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
Acked-by: Cong Wang <xiyou.wangcong@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 net/sched/act_api.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 15d46b9166de..0a31f2c51e94 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -814,10 +814,8 @@ static int tca_action_flush(struct net *net, struct nlattr *nla,
 		goto out_module_put;
 
 	err = a->ops->walk(skb, &dcb, RTM_DELACTION, a);
-	if (err < 0)
+	if (err <= 0)
 		goto out_module_put;
-	if (err == 0)
-		goto noflush_out;
 
 	nla_nest_end(skb, nest);
 
@@ -835,7 +833,6 @@ static int tca_action_flush(struct net *net, struct nlattr *nla,
 out_module_put:
 	module_put(a->ops->owner);
 err_out:
-noflush_out:
 	kfree_skb(skb);
 	kfree(a);
 	return err;
-- 
2.12.2