Patch "xfrm: move xfrm_garbage_collect out of xfrm_policy_flush" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

xfrm: move xfrm_garbage_collect out of xfrm_policy_flush

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xfrm-move-xfrm_garbage_collect-out-of-xfrm_policy_flush.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Hangbin Liu <[email protected]>
Date: Sun, 11 Jun 2017 09:44:20 +0800
Subject: xfrm: move xfrm_garbage_collect out of xfrm_policy_flush

From: Hangbin Liu <[email protected]>

commit 138437f591dd9a42d53c6fed1a3c85e02678851c upstream.

Now we will force to do garbage collection if any policy removed in xfrm_policy_flush(). But during xfrm_net_exit(). We call flow_cache_fini() first and set set fc->percpu to NULL. Then after we call xfrm_policy_fini() -> frxm_policy_flush() -> flow_cache_flush(), we will get NULL pointer dereference when check percpu_empty. The code path looks like:

flow_cache_fini()
- fc->percpu = NULL
xfrm_policy_fini()
- xfrm_policy_flush()
- xfrm_garbage_collect()
- flow_cache_flush()
- flow_cache_percpu_empty()
- fcp = per_cpu_ptr(fc->percpu, cpu)

To reproduce, just add ipsec in netns and then remove the netns.

v2:
As Xin Long suggested, since only two other places need to call it. move xfrm_garbage_collect() outside xfrm_policy_flush().

v3:
Fix subject mismatch after v2 fix.

---
 net/key/af_key.c       |    2 ++
 net/xfrm/xfrm_policy.c |    4 ----
 net/xfrm/xfrm_user.c   |    1 +
 3 files changed, 3 insertions(+), 4 deletions(-)

@@ -2755,6 +2755,8 @@ static int pfkey_spdflush(struct sock *s
 	int err, err2;
 
 	err = xfrm_policy_flush(net, XFRM_POLICY_TYPE_MAIN, true);
+	if (!err)
+		xfrm_garbage_collect(net);
 	err2 = unicast_flush_resp(sk, hdr);
 	if (err || err2) {
 		if (err == -ESRCH) /* empty table - old silent behavior */

@@ -1006,10 +1006,6 @@ int xfrm_policy_flush(struct net *net, u
 		err = -ESRCH;
 out:
 	spin_unlock_bh(&net->xfrm.xfrm_policy_lock);
-
-	if (cnt)
-		xfrm_garbage_collect(net);
-
 	return err;
 }
 EXPORT_SYMBOL(xfrm_policy_flush);

@@ -1999,6 +1999,7 @@ static int xfrm_flush_policy(struct sk_b
 			return 0;
 		return err;
 	}
+	xfrm_garbage_collect(net);
 
 	c.data.type = type;
 	c.event = nlh->nlmsg_type;

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/xfrm-move-xfrm_garbage_collect-out-of-xfrm_policy_flush.patch