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

[ Upstream commits 1be374a0518a288147c6a7398792583200a67261 and
  a7526eb5d06b0084ef12d7b168d008fcf516caab ]

MSG_CMSG_COMPAT is (AFAIK) not intended to be part of the API --
it's a hack that steals a bit to indicate to other networking code
that a compat entry was used.  So don't allow it from a non-compat
syscall.

This prevents an oops when running this code:

int main()
{
	int s;
	struct sockaddr_in addr;
	struct msghdr *hdr;

	char *highpage = mmap((void*)(TASK_SIZE_MAX - 4096), 4096,
	                      PROT_READ | PROT_WRITE,
	                      MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
	if (highpage == MAP_FAILED)
		err(1, "mmap");

	s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (s == -1)
		err(1, "socket");

        addr.sin_family = AF_INET;
        addr.sin_port = htons(1);
        addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
	if (connect(s, (struct sockaddr*)&addr, sizeof(addr)) != 0)
		err(1, "connect");

	void *evil = highpage + 4096 - COMPAT_MSGHDR_SIZE;
	printf("Evil address is %p\n", evil);

	if (syscall(__NR_sendmmsg, s, evil, 1, MSG_CMSG_COMPAT) < 0)
		err(1, "sendmmsg");

	return 0;
}

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 2acd2e2..7e9f2d3 100644 (file)
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -336,6 +336,9 @@ extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
 
 struct timespec;
 
 
 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,
 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 6def90e..8c979cc 100644 (file)
--- a/net/compat.c
+++ b/net/compat.c
@@ -733,19 +733,25 @@ static unsigned char nas[21] = {
 
 asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned flags)
 {
 
 asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned 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 vlen, unsigned int flags)
 {
 }
 
 asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg,
                                    unsigned 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_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 flags)
 }
 
 asmlinkage long compat_sys_recv(int fd, void __user *buf, size_t len, unsigned flags)


@@ -767,6 +773,9 @@ asmlinkage long compat_sys_recvmmsg(int fd, struct compat_mmsghdr __user *mmsg,
        int datagrams;
        struct timespec ktspec;
 
        int datagrams;
        struct timespec ktspec;
 

+       if (flags & MSG_CMSG_COMPAT)
+               return -EINVAL;
+

        if (timeout == NULL)
                return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
                                      flags | MSG_CMSG_COMPAT, NULL);
        if (timeout == NULL)
                return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
                                      flags | MSG_CMSG_COMPAT, NULL);

diff --git a/net/socket.c b/net/socket.c
index 68879db..cf546a3 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -1876,9 +1876,9 @@ struct used_address {
        unsigned int name_len;
 };
 
        unsigned int name_len;
 };
 

-static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
-                        struct msghdr *msg_sys, unsigned flags,
-                        struct used_address *used_address)
+static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
+                         struct msghdr *msg_sys, unsigned flags,
+                         struct used_address *used_address)

 {
        struct compat_msghdr __user *msg_compat =
            (struct compat_msghdr __user *)msg;
 {
        struct compat_msghdr __user *msg_compat =
            (struct compat_msghdr __user *)msg;


@@ -1998,22 +1998,30 @@ out:
  *     BSD sendmsg interface
  */
 
  *     BSD sendmsg interface
  */
 

-SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned, flags)
+long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)

 {
        int fput_needed, err;
        struct msghdr msg_sys;
 {
        int fput_needed, err;
        struct msghdr msg_sys;

-       struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed);
+       struct socket *sock;

 
 

+       sock = sockfd_lookup_light(fd, &err, &fput_needed);

        if (!sock)
                goto out;
 
        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;
 }
 
 
        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
  */
 /*
  *     Linux sendmmsg interface
  */


@@ -2044,15 +2052,16 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
 
        while (datagrams < vlen) {
                if (MSG_CMSG_COMPAT & flags) {
 
        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 {
                        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);
                        if (err < 0)
                                break;
                        err = put_user(err, &entry->msg_len);


@@ -2076,11 +2085,13 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
 SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
                unsigned int, vlen, unsigned int, flags)
 {
 SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
                unsigned int, vlen, unsigned int, flags)
 {

+       if (flags & MSG_CMSG_COMPAT)
+               return -EINVAL;

        return __sys_sendmmsg(fd, mmsg, vlen, flags);
 }
 
        return __sys_sendmmsg(fd, mmsg, vlen, flags);
 }
 

-static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
-                        struct msghdr *msg_sys, unsigned flags, int nosec)
+static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
+                         struct msghdr *msg_sys, unsigned flags, int nosec)

 {
        struct compat_msghdr __user *msg_compat =
            (struct compat_msghdr __user *)msg;
 {
        struct compat_msghdr __user *msg_compat =
            (struct compat_msghdr __user *)msg;


@@ -2177,23 +2188,31 @@ out:
  *     BSD recvmsg interface
  */
 
  *     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;
 {
        int fput_needed, err;
        struct msghdr msg_sys;

-       struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed);
+       struct socket *sock;

 
 

+       sock = sockfd_lookup_light(fd, &err, &fput_needed);

        if (!sock)
                goto out;
 
        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;
 }
 
 
        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
  */
 /*
  *     Linux recvmmsg interface
  */


@@ -2231,17 +2250,18 @@ 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) {
                 * 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 {
                        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);
                        if (err < 0)
                                break;
                        err = put_user(err, &entry->msg_len);


@@ -2308,6 +2328,9 @@ SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg,
        int datagrams;
        struct timespec timeout_sys;
 
        int datagrams;
        struct timespec timeout_sys;
 

+       if (flags & MSG_CMSG_COMPAT)
+               return -EINVAL;
+

        if (!timeout)
                return __sys_recvmmsg(fd, mmsg, vlen, flags, NULL);
 
        if (!timeout)
                return __sys_recvmmsg(fd, mmsg, vlen, flags, NULL);