selinux: add a skb_owned_by() hook

Commit 90ba9b1986b5ac (tcp: tcp_make_synack() can use alloc_skb())
broke certain SELinux/NetLabel configurations by no longer correctly
assigning the sock to the outgoing SYNACK packet.

Cost of atomic operations on the LISTEN socket is quite big,
and we would like it to happen only if really needed.

This patch introduces a new security_ops->skb_owned_by() method,
that is a void operation unless selinux is active.

Reported-by: Miroslav Vadkerti <mvadkert@redhat.com>
Diagnosed-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-security-module@vger.kernel.org
Acked-by: James Morris <james.l.morris@oracle.com>
Tested-by: Paul Moore <pmoore@redhat.com>
Acked-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 18 insertions, 0 deletions

diff --git a/security/capability.c b/security/capability.c
index 579775088967..6783c3e6c88e 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -737,6 +737,11 @@ static int cap_tun_dev_open(void *security)
 {
         return 0;
 }
+
+static void cap_skb_owned_by(struct sk_buff *skb, struct sock *sk)
+{
+}
+
 #endif  /* CONFIG_SECURITY_NETWORK */
 
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
@@ -1071,6 +1076,7 @@ void __init security_fixup_ops(struct security_operations *ops)
         set_to_cap_if_null(ops, tun_dev_open);
         set_to_cap_if_null(ops, tun_dev_attach_queue);
         set_to_cap_if_null(ops, tun_dev_attach);
+        set_to_cap_if_null(ops, skb_owned_by);
 #endif  /* CONFIG_SECURITY_NETWORK */
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
         set_to_cap_if_null(ops, xfrm_policy_alloc_security);
diff --git a/security/security.c b/security/security.c
index 7b88c6aeaed4..03f248b84e9f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1290,6 +1290,11 @@ int security_tun_dev_open(void *security)
 }
 EXPORT_SYMBOL(security_tun_dev_open);
 
+void security_skb_owned_by(struct sk_buff *skb, struct sock *sk)
+{
+        security_ops->skb_owned_by(skb, sk);
+}
+
 #endif  /* CONFIG_SECURITY_NETWORK */
 
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 2fa28c88900c..7171a957b933 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -51,6 +51,7 @@
 #include <linux/tty.h>
 #include <net/icmp.h>
 #include <net/ip.h>             /* for local_port_range[] */
+#include <net/sock.h>
 #include <net/tcp.h>            /* struct or_callable used in sock_rcv_skb */
 #include <net/net_namespace.h>
 #include <net/netlabel.h>
@@ -4363,6 +4364,11 @@ static void selinux_inet_conn_established(struct sock *sk, struct sk_buff *skb)
         selinux_skb_peerlbl_sid(skb, family, &sksec->peer_sid);
 }
 
+static void selinux_skb_owned_by(struct sk_buff *skb, struct sock *sk)
+{
+        skb_set_owner_w(skb, sk);
+}
+
 static int selinux_secmark_relabel_packet(u32 sid)
 {
         const struct task_security_struct *__tsec;
@@ -5664,6 +5670,7 @@ static struct security_operations selinux_ops = {
         .tun_dev_attach_queue =         selinux_tun_dev_attach_queue,
         .tun_dev_attach =               selinux_tun_dev_attach,
         .tun_dev_open =                 selinux_tun_dev_open,
+        .skb_owned_by =                 selinux_skb_owned_by,
 
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
         .xfrm_policy_alloc_security =   selinux_xfrm_policy_alloc,