Disable fd sharing for this release. Sorry.

deraadt@ ok.

3 files changed, 23 insertions, 3 deletions

diff --git a/lib/libc/sys/rfork.2 b/lib/libc/sys/rfork.2
index dfc8313953f..39cda812b45 100644
--- a/lib/libc/sys/rfork.2
+++ b/lib/libc/sys/rfork.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: rfork.2,v 1.15 2000/10/18 05:12:11 aaron Exp $
+.\"	$OpenBSD: rfork.2,v 1.16 2001/10/14 14:39:03 art Exp $
 .\"
 .\" This manual page is taken directly from Plan9, and modified to
 .\" describe the actual OpenBSD implementation.  Permission for
@@ -52,6 +52,11 @@ If set, the invoker's file descriptor table (see
 .Xr intro 2 )
 is copied; otherwise the two processes share a
 single table.
+This flag is currently disabled in the kernel for security reasons and needs
+a special kernel compile option to work.
+Please consult
+.Xr options 4
+for information about the RFORK_FDSHARE option.
 .It Dv RFCFDG
 If set, the new process starts with a clean file descriptor table.
 Is mutually exclusive with
diff --git a/share/man/man4/options.4 b/share/man/man4/options.4
index 8a8b8d4876b..6afef675a0c 100644
--- a/share/man/man4/options.4
+++ b/share/man/man4/options.4
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: options.4,v 1.84 2001/10/05 14:45:53 mpech Exp $
+.\"	$OpenBSD: options.4,v 1.85 2001/10/14 14:39:03 art Exp $
 .\"	$NetBSD: options.4,v 1.21 1997/06/25 03:13:00 thorpej Exp $
 .\"
 .\" Copyright (c) 1998 Theo de Raadt
@@ -996,6 +996,14 @@ status can still be obtained using
 .Xr apm 8
 and/or
 .Xr apmd 8 .
+.It Cd RFORK_FDSHARE
+This option enables sharing of filedescriptor tables between processes that
+request it.
+It is needed for the
+.Xr rfork
+system call to work properly and for some programs run under Linux emulation.
+It's disabled by default for security reasons because it allows any malicious
+user to crash the system.
 .El
 .\" The following requests should be uncommented and used where appropriate.
 .\" .Sh FILES
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 20921bd35d7..38fae5329ea 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_fork.c,v 1.43 2001/09/19 20:50:58 mickey Exp $	*/
+/*	$OpenBSD: kern_fork.c,v 1.44 2001/10/14 14:39:03 art Exp $	*/
 /*	$NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $	*/
 
 /*
@@ -152,6 +152,13 @@ fork1(p1, exitsig, flags, stack, stacksize, retval)
 	extern void endtsleep __P((void *));
 	extern void realitexpire __P((void *));
 
+#ifndef RFORK_FDSHARE
+	/* XXX - Too dangerous right now. */
+	if (flags & FORK_SHAREFILES) {
+		return (EOPNOTSUPP);
+	}
+#endif
+
 	/*
 	 * Although process entries are dynamically created, we still keep
 	 * a global limit on the maximum number we will create. We reserve