net: Unbreak compat_sys_{send,recv}msg

I broke them in this commit:

    commit 1be374a0518a288147c6a7398792583200a67261
    Author: Andy Lutomirski <luto@amacapital.net>
    Date:   Wed May 22 14:07:44 2013 -0700

        net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg

This patch adds __sys_sendmsg and __sys_sendmsg as common helpers that accept
MSG_CMSG_COMPAT and blocks MSG_CMSG_COMPAT at the syscall entrypoints.  It
also reverts some unnecessary checks in sys_socketcall.

Apparently I was suffering from underscore blindness the first time around.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Tested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 47 insertions, 41 deletions

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 33bf2dfab19d..b10ce4b341ea 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -320,6 +320,9 @@ extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
 
 struct timespec;
 
+/* The __sys_...msg variants allow MSG_CMSG_COMPAT */
+extern long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags);
+extern long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags);
 extern int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
                           unsigned int flags, struct timespec *timeout);
 extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
diff --git a/net/compat.c b/net/compat.c
index 79ae88485001..f0a1ba6c8086 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -734,19 +734,25 @@ static unsigned char nas[21] = {
 
 asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned int flags)
 {
-        return sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
+        if (flags & MSG_CMSG_COMPAT)
+                return -EINVAL;
+        return __sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
 }
 
 asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg,
                                     unsigned int vlen, unsigned int flags)
 {
+        if (flags & MSG_CMSG_COMPAT)
+                return -EINVAL;
         return __sys_sendmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
                               flags | MSG_CMSG_COMPAT);
 }
 
 asmlinkage long compat_sys_recvmsg(int fd, struct compat_msghdr __user *msg, unsigned int flags)
 {
-        return sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
+        if (flags & MSG_CMSG_COMPAT)
+                return -EINVAL;
+        return __sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
 }
 
 asmlinkage long compat_sys_recv(int fd, void __user *buf, size_t len, unsigned int flags)
@@ -768,6 +774,9 @@ asmlinkage long compat_sys_recvmmsg(int fd, struct compat_mmsghdr __user *mmsg,
         int datagrams;
         struct timespec ktspec;
 
+        if (flags & MSG_CMSG_COMPAT)
+                return -EINVAL;
+
         if (COMPAT_USE_64BIT_TIME)
                 return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
                                       flags | MSG_CMSG_COMPAT,
diff --git a/net/socket.c b/net/socket.c
index 9ff6366fee13..4ca1526db756 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1956,7 +1956,7 @@ struct used_address {
         unsigned int name_len;
 };
 
-static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
+static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
                          struct msghdr *msg_sys, unsigned int flags,
                          struct used_address *used_address)
 {
@@ -2071,26 +2071,30 @@ out:
  *      BSD sendmsg interface
  */
 
-SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags)
+long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
 {
         int fput_needed, err;
         struct msghdr msg_sys;
         struct socket *sock;
 
-        if (flags & MSG_CMSG_COMPAT)
-                return -EINVAL;
-
         sock = sockfd_lookup_light(fd, &err, &fput_needed);
         if (!sock)
                 goto out;
 
-        err = __sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
+        err = ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
 
         fput_light(sock->file, fput_needed);
 out:
         return err;
 }
 
+SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags)
+{
+        if (flags & MSG_CMSG_COMPAT)
+                return -EINVAL;
+        return __sys_sendmsg(fd, msg, flags);
+}
+
 /*
  *      Linux sendmmsg interface
  */
@@ -2121,15 +2125,16 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
 
         while (datagrams < vlen) {
                 if (MSG_CMSG_COMPAT & flags) {
-                        err = __sys_sendmsg(sock, (struct msghdr __user *)compat_entry,
-                                            &msg_sys, flags, &used_address);
+                        err = ___sys_sendmsg(sock, (struct msghdr __user *)compat_entry,
+                                             &msg_sys, flags, &used_address);
                         if (err < 0)
                                 break;
                         err = __put_user(err, &compat_entry->msg_len);
                         ++compat_entry;
                 } else {
-                        err = __sys_sendmsg(sock, (struct msghdr __user *)entry,
-                                            &msg_sys, flags, &used_address);
+                        err = ___sys_sendmsg(sock,
+                                             (struct msghdr __user *)entry,
+                                             &msg_sys, flags, &used_address);
                         if (err < 0)
                                 break;
                         err = put_user(err, &entry->msg_len);
@@ -2158,7 +2163,7 @@ SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
         return __sys_sendmmsg(fd, mmsg, vlen, flags);
 }
 
-static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
+static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
                          struct msghdr *msg_sys, unsigned int flags, int nosec)
 {
         struct compat_msghdr __user *msg_compat =
@@ -2250,27 +2255,31 @@ out:
  *      BSD recvmsg interface
  */
 
-SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
-                unsigned int, flags)
+long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags)
 {
         int fput_needed, err;
         struct msghdr msg_sys;
         struct socket *sock;
 
-        if (flags & MSG_CMSG_COMPAT)
-                return -EINVAL;
-
         sock = sockfd_lookup_light(fd, &err, &fput_needed);
         if (!sock)
                 goto out;
 
-        err = __sys_recvmsg(sock, msg, &msg_sys, flags, 0);
+        err = ___sys_recvmsg(sock, msg, &msg_sys, flags, 0);
 
         fput_light(sock->file, fput_needed);
 out:
         return err;
 }
 
+SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
+                unsigned int, flags)
+{
+        if (flags & MSG_CMSG_COMPAT)
+                return -EINVAL;
+        return __sys_recvmsg(fd, msg, flags);
+}
+
 /*
  *     Linux recvmmsg interface
  */
@@ -2308,17 +2317,18 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
                  * No need to ask LSM for more than the first datagram.
                  */
                 if (MSG_CMSG_COMPAT & flags) {
-                        err = __sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
-                                            &msg_sys, flags & ~MSG_WAITFORONE,
-                                            datagrams);
+                        err = ___sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
+                                             &msg_sys, flags & ~MSG_WAITFORONE,
+                                             datagrams);
                         if (err < 0)
                                 break;
                         err = __put_user(err, &compat_entry->msg_len);
                         ++compat_entry;
                 } else {
-                        err = __sys_recvmsg(sock, (struct msghdr __user *)entry,
-                                            &msg_sys, flags & ~MSG_WAITFORONE,
-                                            datagrams);
+                        err = ___sys_recvmsg(sock,
+                                             (struct msghdr __user *)entry,
+                                             &msg_sys, flags & ~MSG_WAITFORONE,
+                                             datagrams);
                         if (err < 0)
                                 break;
                         err = put_user(err, &entry->msg_len);
@@ -2505,31 +2515,15 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
                                    (int __user *)a[4]);
                 break;
         case SYS_SENDMSG:
-                if (a[2] & MSG_CMSG_COMPAT) {
-                        err = -EINVAL;
-                        break;
-                }
                 err = sys_sendmsg(a0, (struct msghdr __user *)a1, a[2]);
                 break;
         case SYS_SENDMMSG:
-                if (a[3] & MSG_CMSG_COMPAT) {
-                        err = -EINVAL;
-                        break;
-                }
                 err = sys_sendmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3]);
                 break;
         case SYS_RECVMSG:
-                if (a[2] & MSG_CMSG_COMPAT) {
-                        err = -EINVAL;
-                        break;
-                }
                 err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
                 break;
         case SYS_RECVMMSG:
-                if (a[3] & MSG_CMSG_COMPAT) {
-                        err = -EINVAL;
-                        break;
-                }
                 err = sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3],
                                    (struct timespec __user *)a[4]);
                 break;