apparmor: fix race between freeing data and fs accessing it

commit 8e135b8aee5a06c52a4347a5a6d51223c6f36ba3 upstream.

AppArmor was putting the reference to i_private data on its end after
removing the original entry from the file system. However the inode
can aand does live beyond that point and it is possible that some of
the fs call back functions will be invoked after the reference has
been put, which results in a race between freeing the data and
accessing it through the fs.

While the rawdata/loaddata is the most likely candidate to fail the
race, as it has the fewest references. If properly crafted it might be
possible to trigger a race for the other types stored in i_private.

Fix this by moving the put of i_private referenced data to the correct
place which is during inode eviction.

Fixes: c961ee5f21b20 ("apparmor: convert from securityfs to apparmorfs for policy ns files")
Reported-by: Qualys Security Advisory <qsa@qualys.com>
Reviewed-by: Georgia Garcia <georgia.garcia@canonical.com>
Reviewed-by: Maxime Bélair <maxime.belair@canonical.com>
Reviewed-by: Cengiz Can <cengiz.can@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/security/apparmor/label.c b/security/apparmor/label.c
index af25ca6b6b83..3bcc45437b44 100644
--- a/security/apparmor/label.c
+++ b/security/apparmor/label.c
@@ -52,7 +52,8 @@ static void free_proxy(struct aa_proxy *proxy)
 
 void aa_proxy_kref(struct kref *kref)
 {
-	struct aa_proxy *proxy = container_of(kref, struct aa_proxy, count);
+	struct aa_proxy *proxy = container_of(kref, struct aa_proxy,
+					      count.count);
 
 	free_proxy(proxy);
 }
@@ -63,7 +64,8 @@ struct aa_proxy *aa_alloc_proxy(struct aa_label *label, gfp_t gfp)
 
 	new = kzalloc(sizeof(struct aa_proxy), gfp);
 	if (new) {
-		kref_init(&new->count);
+		kref_init(&new->count.count);
+		new->count.reftype = REF_PROXY;
 		rcu_assign_pointer(new->label, aa_get_label(label));
 	}
 	return new;
@@ -371,7 +373,8 @@ static void label_free_rcu(struct rcu_head *head)
 
 void aa_label_kref(struct kref *kref)
 {
-	struct aa_label *label = container_of(kref, struct aa_label, count);
+	struct aa_label *label = container_of(kref, struct aa_label,
+					      count.count);
 	struct aa_ns *ns = labels_ns(label);
 
 	if (!ns) {
@@ -408,7 +411,8 @@ bool aa_label_init(struct aa_label *label, int size, gfp_t gfp)
 
 	label->size = size;			/* doesn't include null */
 	label->vec[size] = NULL;		/* null terminate */
-	kref_init(&label->count);
+	kref_init(&label->count.count);
+	label->count.reftype = REF_NS;		/* for aafs purposes */
 	RB_CLEAR_NODE(&label->node);
 
 	return true;