: nf_conntrack: fix use-after-free in helper destroy callback invocation

These two patches fix an oops when unloading helper modules and a incorrect config ifdef.

Please apply, thanks.

[NETFILTER]: nf_conntrack: fix use-after-free in helper destroy callback invocation

When the helper module is removed for a master connection that has a fulfilled expectation, but has already timed out and got removed from the hash tables, nf_conntrack_helper_unregister can't find the master connection to unset the helper, causing a use-after-free when the expected connection is destroyed and releases the last reference to the master.

The helper destroy callback was introduced for the PPtP helper to clean up expectations and expected connections when the master connection times out, but doing this from destroy_conntrack only works for unfulfilled expectations since expected connections hold a reference to the master, preventing its destruction. Move the destroy callback to the timeout function, which fixes both problems.

Reported/tested by Gabor Burjan <[email protected]>.

---
commit a49738a0ca6dbe54bbc6672b52286ed6b1d8f4ce
tree aa2324f3dd628d3b74f6c6d57355b11adb2212d3
parent af3b146d26550f0c8e0d77b2117c6f8aec5d8146
author Patrick McHardy <[email protected]> Wed, 16 May 2007 18:51:42 +0200 committer Patrick McHardy <[email protected]> Wed, 16 May 2007 18:51:42 +0200

 net/netfilter/nf_conntrack_core.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

index e8b5c2d..483e927 100644
@@ -298,7 +298,6 @@ static void
 destroy_conntrack(struct nf_conntrack *nfct)
 {
 	struct nf_conn *ct = (struct nf_conn *)nfct;
-	struct nf_conn_help *help = nfct_help(ct);
 	struct nf_conntrack_l4proto *l4proto;
 	typeof(nf_conntrack_destroyed) destroyed;
 

@@ -309,9 +308,6 @@ destroy_conntrack(struct nf_conntrack *nfct)
 	nf_conntrack_event(IPCT_DESTROY, ct);
 	set_bit(IPS_DYING_BIT, &ct->status);
 
-	if (help && help->helper && help->helper->destroy)
-		help->helper->destroy(ct);
-
 	/* To make sure we don't get any weird locking issues here:
 	 * destroy_conntrack() MUST NOT be called with a write lock
 	 * to nf_conntrack_lock!!! -HW */

@@ -353,6 +349,10 @@ destroy_conntrack(struct nf_conntrack *nfct)
 static void death_by_timeout(unsigned long ul_conntrack)
 {
 	struct nf_conn *ct = (void *)ul_conntrack;
+	struct nf_conn_help *help = nfct_help(ct);
+
+	if (help && help->helper && help->helper->destroy)
+		help->helper->destroy(ct);
 
 	write_lock_bh(&nf_conntrack_lock);
 	/* Inside lock so preempt is disabled on module removal path.

From: Patrick McHardy <[email protected]>
Date: Wed, 16 May 2007 18:54:37 +0200

Both applied, thanks a lot Patrick.