audit: log 32-bit socketcalls

32-bit socketcalls were not being logged by audit on x86_64 systems.
Log them.  This is basically a duplicate of the call from
net/socket.c:sys_socketcall(), but it addresses the impedance mismatch
between 32-bit userspace process and 64-bit kernel audit.

See: https://github.com/linux-audit/audit-kernel/issues/14

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Moore <paul@paul-moore.com>

include/linux/audit.h

@@ -387,6 +387,20 @@ static inline int audit_socketcall(int nargs, unsigned long *args)
 		return __audit_socketcall(nargs, args);
 	return 0;
 }
+
+static inline int audit_socketcall_compat(int nargs, u32 *args)
+{
+	unsigned long a[AUDITSC_ARGS];
+	int i;
+
+	if (audit_dummy_context())
+		return 0;
+
+	for (i = 0; i < nargs; i++)
+		a[i] = (unsigned long)args[i];
+	return __audit_socketcall(nargs, a);
+}
+
 static inline int audit_sockaddr(int len, void *addr)
 {
 	if (unlikely(!audit_dummy_context()))
@@ -513,6 +527,12 @@ static inline int audit_socketcall(int nargs, unsigned long *args)
 {
 	return 0;
 }
+
+static inline int audit_socketcall_compat(int nargs, u32 *args)
+{
+	return 0;
+}
+
 static inline void audit_fd_pair(int fd1, int fd2)
 { }
 static inline int audit_sockaddr(int len, void *addr)

net/compat.c

@@ -22,6 +22,7 @@
 #include <linux/filter.h>
 #include <linux/compat.h>
 #include <linux/security.h>
+#include <linux/audit.h>
 #include <linux/export.h>
 
 #include <net/scm.h>
@@ -781,14 +782,24 @@ COMPAT_SYSCALL_DEFINE5(recvmmsg, int, fd, struct compat_mmsghdr __user *, mmsg,
 
 COMPAT_SYSCALL_DEFINE2(socketcall, int, call, u32 __user *, args)
 {
-	int ret;
-	u32 a[6];
+	u32 a[AUDITSC_ARGS];
+	unsigned int len;
 	u32 a0, a1;
+	int ret;
 
 	if (call < SYS_SOCKET || call > SYS_SENDMMSG)
 		return -EINVAL;
-	if (copy_from_user(a, args, nas[call]))
+	len = nas[call];
+	if (len > sizeof(a))
+		return -EINVAL;
+
+	if (copy_from_user(a, args, len))
 		return -EFAULT;
+
+	ret = audit_socketcall_compat(len / sizeof(a[0]), a);
+	if (ret)
+		return ret;
+
 	a0 = a[0];
 	a1 = a[1];