apparmor: fix fast path cache check for unix sockets

The fast path cache check is incorrect forcing more slow path
revalidations than necessary, because the unix logic check is inverted.

Reviewed-by: Georgia Garcia <georgia.garcia@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

1 files changed, 21 insertions, 14 deletions

diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index c751f2774c59..694e157149e8 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -572,8 +572,7 @@ static bool __file_is_delegated(struct aa_label *obj_label)
 	return unconfined(obj_label);
 }
 
-static bool __unix_needs_revalidation(struct file *file, struct aa_label *label,
-				      u32 request)
+static bool __is_unix_file(struct file *file)
 {
 	struct socket *sock = (struct socket *) file->private_data;
 
@@ -581,23 +580,31 @@ static bool __unix_needs_revalidation(struct file *file, struct aa_label *label,
 
 	if (!S_ISSOCK(file_inode(file)->i_mode))
 		return false;
-	if (request & NET_PEER_MASK)
-		return false;
 	/* sock and sock->sk can be NULL for sockets being set up or torn down */
 	if (!sock || !sock->sk)
 		return false;
-	if (sock->sk->sk_family == PF_UNIX) {
-		struct aa_sk_ctx *ctx = aa_sock(sock->sk);
-
-		if (rcu_access_pointer(ctx->peer) !=
-		    rcu_access_pointer(ctx->peer_lastupdate))
-			return true;
-		return !__aa_subj_label_is_cached(rcu_dereference(ctx->label),
-						  label);
-	}
+	if (sock->sk->sk_family == PF_UNIX)
+		return true;
 	return false;
 }
 
+static bool __unix_needs_revalidation(struct file *file, struct aa_label *label,
+				      u32 request)
+{
+	struct socket *sock = (struct socket *) file->private_data;
+
+	AA_BUG(!__is_unix_file(file));
+	lockdep_assert_in_rcu_read_lock();
+
+	struct aa_sk_ctx *skctx = aa_sock(sock->sk);
+
+	if (rcu_access_pointer(skctx->peer) !=
+	    rcu_access_pointer(skctx->peer_lastupdate))
+		return true;
+
+	return !__aa_subj_label_is_cached(rcu_dereference(skctx->label), label);
+}
+
 /**
  * aa_file_perm - do permission revalidation check & audit for @file
  * @op: operation being checked
@@ -640,7 +647,7 @@ int aa_file_perm(const char *op, const struct cred *subj_cred,
 	 */
 	denied = request & ~fctx->allow;
 	if (unconfined(label) || __file_is_delegated(flabel) ||
-	    __unix_needs_revalidation(file, label, request) ||
+	    (!denied && __is_unix_file(file) && !__unix_needs_revalidation(file, label, request)) ||
 	    (!denied && __aa_subj_label_is_cached(label, flabel))) {
 		rcu_read_unlock();
 		goto done;