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Implement SOCK_CLOEXEC, SOCK_NONBLOCK and MSG_CMSG_CLOEXEC.

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This change allows creating file descriptors with close-on-exec set in some
situations. SOCK_CLOEXEC and SOCK_NONBLOCK can be OR'ed in socket() and
socketpair()'s type parameter, and MSG_CMSG_CLOEXEC to recvmsg() makes file
descriptors (SCM_RIGHTS) atomically close-on-exec.

The numerical values for SOCK_CLOEXEC and SOCK_NONBLOCK are as in NetBSD.
MSG_CMSG_CLOEXEC is the first free bit for MSG_*.

The SOCK_* flags are not passed to MAC because this may cause incorrect
failures and can be done later via fcntl() anyway. On the other hand, audit
is expected to cope with the new flags.

For MSG_CMSG_CLOEXEC, unp_externalize() is extended to take a flags
argument.

Reviewed by:	kib
This commit is contained in:
Jilles Tjoelker 2013-03-19 20:58:17 +00:00
parent f0db652cf6
commit c2e3c52e0d
9 changed files with 95 additions and 27 deletions
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9
lib/libc/sys/recv.2
View File

@ -28,7 +28,7 @@
.\" @(#)recv.2 8.3 (Berkeley) 2/21/94
.\" $FreeBSD$
.\"
.Dd September 12, 2012
.Dd March 19, 2013
.Dt RECV 2
.Os
.Sh NAME
@ -121,11 +121,12 @@ argument to a
function is formed by
.Em or Ap ing
one or more of the values:
.Bl -column ".Dv MSG_DONTWAIT" -offset indent
.Bl -column ".Dv MSG_CMSG_CLOEXEC" -offset indent
.It Dv MSG_OOB Ta process out-of-band data
.It Dv MSG_PEEK Ta peek at incoming message
.It Dv MSG_WAITALL Ta wait for full request or error
.It Dv MSG_DONTWAIT Ta do not block
.It Dv MSG_CMSG_CLOEXEC Ta set received fds close-on-exec
.El
.Pp
The
@ -227,6 +228,10 @@ and
.Fa cmsg_type
set to
.Dv SCM_RIGHTS .
The close-on-exec flag on received descriptors is set according to the
.Dv MSG_CMSG_CLOEXEC
flag passed to
.Fn recvmsg .
.Pp
Process credentials can also be passed as ancillary data for
.Dv AF_UNIX

11
lib/libc/sys/socket.2
View File

@ -28,7 +28,7 @@
.\" From: @(#)socket.2 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd December 7, 2012
.Dd March 19, 2013
.Dt SOCKET 2
.Os
.Sh NAME
@ -115,6 +115,15 @@ which is available only to the super-user, and
which is planned,
but not yet implemented, are not described here.
.Pp
Additionally, the following flags are allowed in the
.Fa type
argument:
.Pp
.Bd -literal -offset indent -compact
SOCK_CLOEXEC Set close-on-exec on the new descriptor,
SOCK_NONBLOCK Set non-blocking mode on the new socket
.Ed
.Pp
The
.Fa protocol
argument

11
lib/libc/sys/socketpair.2
View File

@ -28,7 +28,7 @@
.\" @(#)socketpair.2 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dd March 19, 2013
.Dt SOCKETPAIR 2
.Os
.Sh NAME
@ -57,6 +57,14 @@ are returned in
and
.Fa sv Ns [1] .
The two sockets are indistinguishable.
.Pp
The
.Dv SOCK_CLOEXEC
and
.Dv SOCK_NONBLOCK
flags in the
.Fa type
argument apply to both descriptors.
.Sh RETURN VALUES
.Rv -std socketpair
.Sh ERRORS
@ -79,6 +87,7 @@ process address space.
.Sh SEE ALSO
.Xr pipe 2 ,
.Xr read 2 ,
.Xr socket 2 ,
.Xr write 2
.Sh HISTORY
The

18
share/man/man4/unix.4
View File

@ -32,7 +32,7 @@
.\" @(#)unix.4 8.1 (Berkeley) 6/9/93
.\" $FreeBSD$
.\"
.Dd November 16, 2012
.Dd March 19, 2013
.Dt UNIX 4
.Os
.Sh NAME
@ -153,13 +153,15 @@ plus the size of the array of file descriptors.
.Pp
The received descriptor is a
.Em duplicate
of the sender's descriptor, as if it were created with a call to
.Xr dup 2 .
Per-process descriptor flags, set with
.Xr fcntl 2 ,
are
.Em not
passed to a receiver.
of the sender's descriptor, as if it were created via
.Li dup(fd)
or
.Li fcntl(fd, F_DUPFD_CLOEXEC, 0)
depending on whether
.Dv MSG_CMSG_CLOEXEC
is passed in the
.Xr recvmsg 2
call.
Descriptors that are awaiting delivery, or that are
purposely not received, are automatically closed by the system
when the destination socket is closed.

4
sys/kern/uipc_socket.c
View File

@ -1727,7 +1727,7 @@ soreceive_generic(struct socket *so, struct sockaddr **psa, struct uio *uio,
SOCKBUF_UNLOCK(&so->so_rcv);
VNET_SO_ASSERT(so);
error = (*pr->pr_domain->dom_externalize)
(cm, controlp);
(cm, controlp, flags);
SOCKBUF_LOCK(&so->so_rcv);
} else if (controlp != NULL)
*controlp = cm;
@ -2361,7 +2361,7 @@ soreceive_dgram(struct socket *so, struct sockaddr **psa, struct uio *uio,
cm->m_next = NULL;
if (pr->pr_domain->dom_externalize != NULL) {
error = (*pr->pr_domain->dom_externalize)
(cm, controlp);
(cm, controlp, flags);
} else if (controlp != NULL)
*controlp = cm;
else

52
sys/kern/uipc_syscalls.c
View File

@ -164,25 +164,40 @@ sys_socket(td, uap)
{
struct socket *so;
struct file *fp;
int fd, error;
int fd, error, type, oflag, fflag;
AUDIT_ARG_SOCKET(uap->domain, uap->type, uap->protocol);
type = uap->type;
oflag = 0;
fflag = 0;
if ((type & SOCK_CLOEXEC) != 0) {
type &= ~SOCK_CLOEXEC;
oflag |= O_CLOEXEC;
}
if ((type & SOCK_NONBLOCK) != 0) {
type &= ~SOCK_NONBLOCK;
fflag |= FNONBLOCK;
}
#ifdef MAC
error = mac_socket_check_create(td->td_ucred, uap->domain, uap->type,
error = mac_socket_check_create(td->td_ucred, uap->domain, type,
uap->protocol);
if (error)
return (error);
#endif
error = falloc(td, &fp, &fd, 0);
error = falloc(td, &fp, &fd, oflag);
if (error)
return (error);
/* An extra reference on `fp' has been held for us by falloc(). */
error = socreate(uap->domain, &so, uap->type, uap->protocol,
error = socreate(uap->domain, &so, type, uap->protocol,
td->td_ucred, td);
if (error) {
fdclose(td->td_proc->p_fd, fp, fd, td);
} else {
finit(fp, FREAD | FWRITE, DTYPE_SOCKET, so, &socketops);
finit(fp, FREAD | FWRITE | fflag, DTYPE_SOCKET, so, &socketops);
if ((fflag & FNONBLOCK) != 0)
(void) fo_ioctl(fp, FIONBIO, &fflag, td->td_ucred, td);
td->td_retval[0] = fd;
}
fdrop(fp, td);
@ -648,9 +663,20 @@ kern_socketpair(struct thread *td, int domain, int type, int protocol,
struct filedesc *fdp = td->td_proc->p_fd;
struct file *fp1, *fp2;
struct socket *so1, *so2;
int fd, error;
int fd, error, oflag, fflag;
AUDIT_ARG_SOCKET(domain, type, protocol);
oflag = 0;
fflag = 0;
if ((type & SOCK_CLOEXEC) != 0) {
type &= ~SOCK_CLOEXEC;
oflag |= O_CLOEXEC;
}
if ((type & SOCK_NONBLOCK) != 0) {
type &= ~SOCK_NONBLOCK;
fflag |= FNONBLOCK;
}
#ifdef MAC
/* We might want to have a separate check for socket pairs. */
error = mac_socket_check_create(td->td_ucred, domain, type,
@ -665,12 +691,12 @@ kern_socketpair(struct thread *td, int domain, int type, int protocol,
if (error)
goto free1;
/* On success extra reference to `fp1' and 'fp2' is set by falloc. */
error = falloc(td, &fp1, &fd, 0);
error = falloc(td, &fp1, &fd, oflag);
if (error)
goto free2;
rsv[0] = fd;
fp1->f_data = so1; /* so1 already has ref count */
error = falloc(td, &fp2, &fd, 0);
error = falloc(td, &fp2, &fd, oflag);
if (error)
goto free3;
fp2->f_data = so2; /* so2 already has ref count */
@ -686,8 +712,14 @@ kern_socketpair(struct thread *td, int domain, int type, int protocol,
if (error)
goto free4;
}
finit(fp1, FREAD | FWRITE, DTYPE_SOCKET, fp1->f_data, &socketops);
finit(fp2, FREAD | FWRITE, DTYPE_SOCKET, fp2->f_data, &socketops);
finit(fp1, FREAD | FWRITE | fflag, DTYPE_SOCKET, fp1->f_data,
&socketops);
finit(fp2, FREAD | FWRITE | fflag, DTYPE_SOCKET, fp2->f_data,
&socketops);
if ((fflag & FNONBLOCK) != 0) {
(void) fo_ioctl(fp1, FIONBIO, &fflag, td->td_ucred, td);
(void) fo_ioctl(fp2, FIONBIO, &fflag, td->td_ucred, td);
}
fdrop(fp1, td);
fdrop(fp2, td);
return (0);

6
sys/kern/uipc_usrreq.c
View File

@ -288,7 +288,7 @@ static void unp_freerights(struct filedescent **, int);
static void unp_init(void);
static int unp_internalize(struct mbuf **, struct thread *);
static void unp_internalize_fp(struct file *);
static int unp_externalize(struct mbuf *, struct mbuf **);
static int unp_externalize(struct mbuf *, struct mbuf **, int);
static int unp_externalize_fp(struct file *);
static struct mbuf *unp_addsockcred(struct thread *, struct mbuf *);
static void unp_process_defers(void * __unused, int);
@ -1695,7 +1695,7 @@ unp_freerights(struct filedescent **fdep, int fdcount)
}
static int
unp_externalize(struct mbuf *control, struct mbuf **controlp)
unp_externalize(struct mbuf *control, struct mbuf **controlp, int flags)
{
struct thread *td = curthread; /* XXX */
struct cmsghdr *cm = mtod(control, struct cmsghdr *);
@ -1765,6 +1765,8 @@ unp_externalize(struct mbuf *control, struct mbuf **controlp)
fde->fde_file = fdep[0]->fde_file;
filecaps_move(&fdep[0]->fde_caps,
&fde->fde_caps);
if ((flags & MSG_CMSG_CLOEXEC) != 0)
fde->fde_flags |= UF_EXCLOSE;
unp_externalize_fp(fde->fde_file);
*fdp = f;
}

2
sys/sys/domain.h
View File

@ -51,7 +51,7 @@ struct domain {
void (*dom_destroy) /* cleanup structures / state */
(void);
int (*dom_externalize) /* externalize access rights */
(struct mbuf *, struct mbuf **);
(struct mbuf *, struct mbuf **, int);
void (*dom_dispose) /* dispose of internalized rights */
(struct mbuf *);
struct protosw *dom_protosw, *dom_protoswNPROTOSW;

9
sys/sys/socket.h
View File

@ -95,6 +95,14 @@ typedef __uid_t uid_t;
#endif
#define SOCK_SEQPACKET 5 /* sequenced packet stream */
#if __BSD_VISIBLE
/*
* Creation flags, OR'ed into socket() and socketpair() type argument.
*/
#define SOCK_CLOEXEC 0x10000000
#define SOCK_NONBLOCK 0x20000000
#endif
/*
* Option flags per-socket.
*/
@ -459,6 +467,7 @@ struct msghdr {
#endif
#if __BSD_VISIBLE
#define MSG_NOSIGNAL 0x20000 /* do not generate SIGPIPE on EOF */
#define MSG_CMSG_CLOEXEC 0x40000 /* make received fds close-on-exec */
#endif
/*