net: separate out the msghdr copy from ___sys_{send,recv}msg()

This is in preparation for enabling the io_uring helpers for sendmsg
and recvmsg to first copy the header for validation before continuing
with the operation.

There should be no functional changes in this patch.

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/net/socket.c b/net/socket.c
index 274df4d..98568ae 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2264,15 +2264,10 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
        return err < 0 ? err : 0;
 }
 
-static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
-                        struct msghdr *msg_sys, unsigned int flags,
-                        struct used_address *used_address,
-                        unsigned int allowed_msghdr_flags)
+static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys,
+                          unsigned int flags, struct used_address *used_address,
+                          unsigned int allowed_msghdr_flags)
 {
-       struct compat_msghdr __user *msg_compat =
-           (struct compat_msghdr __user *)msg;
-       struct sockaddr_storage address;
-       struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
        unsigned char ctl[sizeof(struct cmsghdr) + 20]
                                __aligned(sizeof(__kernel_size_t));
        /* 20 is size of ipv6_pktinfo */
@@ -2280,19 +2275,10 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
        int ctl_len;
        ssize_t err;
 
-       msg_sys->msg_name = &address;
-
-       if (MSG_CMSG_COMPAT & flags)
-               err = get_compat_msghdr(msg_sys, msg_compat, NULL, &iov);
-       else
-               err = copy_msghdr_from_user(msg_sys, msg, NULL, &iov);
-       if (err < 0)
-               return err;
-
        err = -ENOBUFS;
 
        if (msg_sys->msg_controllen > INT_MAX)
-               goto out_freeiov;
+               goto out;
        flags |= (msg_sys->msg_flags & allowed_msghdr_flags);
        ctl_len = msg_sys->msg_controllen;
        if ((MSG_CMSG_COMPAT & flags) && ctl_len) {
@@ -2300,7 +2286,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
                    cmsghdr_from_user_compat_to_kern(msg_sys, sock->sk, ctl,
                                                     sizeof(ctl));
                if (err)
-                       goto out_freeiov;
+                       goto out;
                ctl_buf = msg_sys->msg_control;
                ctl_len = msg_sys->msg_controllen;
        } else if (ctl_len) {
@@ -2309,7 +2295,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
                if (ctl_len > sizeof(ctl)) {
                        ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL);
                        if (ctl_buf == NULL)
-                               goto out_freeiov;
+                               goto out;
                }
                err = -EFAULT;
                /*
@@ -2355,7 +2341,47 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
 out_freectl:
        if (ctl_buf != ctl)
                sock_kfree_s(sock->sk, ctl_buf, ctl_len);
-out_freeiov:
+out:
+       return err;
+}
+
+static int sendmsg_copy_msghdr(struct msghdr *msg,
+                              struct user_msghdr __user *umsg, unsigned flags,
+                              struct iovec **iov)
+{
+       int err;
+
+       if (flags & MSG_CMSG_COMPAT) {
+               struct compat_msghdr __user *msg_compat;
+
+               msg_compat = (struct compat_msghdr __user *) umsg;
+               err = get_compat_msghdr(msg, msg_compat, NULL, iov);
+       } else {
+               err = copy_msghdr_from_user(msg, umsg, NULL, iov);
+       }
+       if (err < 0)
+               return err;
+
+       return 0;
+}
+
+static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
+                        struct msghdr *msg_sys, unsigned int flags,
+                        struct used_address *used_address,
+                        unsigned int allowed_msghdr_flags)
+{
+       struct sockaddr_storage address;
+       struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+       ssize_t err;
+
+       msg_sys->msg_name = &address;
+
+       err = sendmsg_copy_msghdr(msg_sys, msg, flags, &iov);
+       if (err < 0)
+               return err;
+
+       err = ____sys_sendmsg(sock, msg_sys, flags, used_address,
+                               allowed_msghdr_flags);
        kfree(iov);
        return err;
 }
@@ -2474,33 +2500,41 @@ SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
        return __sys_sendmmsg(fd, mmsg, vlen, flags, true);
 }
 
-static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
-                        struct msghdr *msg_sys, unsigned int flags, int nosec)
+static int recvmsg_copy_msghdr(struct msghdr *msg,
+                              struct user_msghdr __user *umsg, unsigned flags,
+                              struct sockaddr __user **uaddr,
+                              struct iovec **iov)
 {
-       struct compat_msghdr __user *msg_compat =
-           (struct compat_msghdr __user *)msg;
-       struct iovec iovstack[UIO_FASTIOV];
-       struct iovec *iov = iovstack;
-       unsigned long cmsg_ptr;
-       int len;
        ssize_t err;
 
-       /* kernel mode address */
-       struct sockaddr_storage addr;
-
-       /* user mode address pointers */
-       struct sockaddr __user *uaddr;
-       int __user *uaddr_len = COMPAT_NAMELEN(msg);
-
-       msg_sys->msg_name = &addr;
+       if (MSG_CMSG_COMPAT & flags) {
+               struct compat_msghdr __user *msg_compat;
 
-       if (MSG_CMSG_COMPAT & flags)
-               err = get_compat_msghdr(msg_sys, msg_compat, &uaddr, &iov);
-       else
-               err = copy_msghdr_from_user(msg_sys, msg, &uaddr, &iov);
+               msg_compat = (struct compat_msghdr __user *) umsg;
+               err = get_compat_msghdr(msg, msg_compat, uaddr, iov);
+       } else {
+               err = copy_msghdr_from_user(msg, umsg, uaddr, iov);
+       }
        if (err < 0)
                return err;
 
+       return 0;
+}
+
+static int ____sys_recvmsg(struct socket *sock, struct msghdr *msg_sys,
+                          struct user_msghdr __user *msg,
+                          struct sockaddr __user *uaddr,
+                          unsigned int flags, int nosec)
+{
+       struct compat_msghdr __user *msg_compat =
+                                       (struct compat_msghdr __user *) msg;
+       int __user *uaddr_len = COMPAT_NAMELEN(msg);
+       struct sockaddr_storage addr;
+       unsigned long cmsg_ptr;
+       int len;
+       ssize_t err;
+
+       msg_sys->msg_name = &addr;
        cmsg_ptr = (unsigned long)msg_sys->msg_control;
        msg_sys->msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
 
@@ -2511,7 +2545,7 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
                flags |= MSG_DONTWAIT;
        err = (nosec ? sock_recvmsg_nosec : sock_recvmsg)(sock, msg_sys, flags);
        if (err < 0)
-               goto out_freeiov;
+               goto out;
        len = err;
 
        if (uaddr != NULL) {
@@ -2519,12 +2553,12 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
                                        msg_sys->msg_namelen, uaddr,
                                        uaddr_len);
                if (err < 0)
-                       goto out_freeiov;
+                       goto out;
        }
        err = __put_user((msg_sys->msg_flags & ~MSG_CMSG_COMPAT),
                         COMPAT_FLAGS(msg));
        if (err)
-               goto out_freeiov;
+               goto out;
        if (MSG_CMSG_COMPAT & flags)
                err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
                                 &msg_compat->msg_controllen);
@@ -2532,10 +2566,25 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
                err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
                                 &msg->msg_controllen);
        if (err)
-               goto out_freeiov;
+               goto out;
        err = len;
+out:
+       return err;
+}
+
+static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
+                        struct msghdr *msg_sys, unsigned int flags, int nosec)
+{
+       struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+       /* user mode address pointers */
+       struct sockaddr __user *uaddr;
+       ssize_t err;
+
+       err = recvmsg_copy_msghdr(msg_sys, msg, flags, &uaddr, &iov);
+       if (err < 0)
+               return err;
 
-out_freeiov:
+       err = ____sys_recvmsg(sock, msg_sys, msg, uaddr, flags, nosec);
        kfree(iov);
        return err;
 }