[PATCH 4.11 56/84] xfrm: move xfrm_garbage_collect out of xfrm_policy_flush

Greg Kroah-Hartman
2017-07-03T13:35:36Z

From: Hangbin Liu <liuhangbin@gmail.com>

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.

Fixes: 35db06912189 ("xfrm: do the garbage collection after flushing policy")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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(-)

--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -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 */
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -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);
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -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;