diff --git a/lib/libsys/jail.2 b/lib/libsys/jail.2
index d3f871608c1d..ee4e5b03d38e 100644
--- a/lib/libsys/jail.2
+++ b/lib/libsys/jail.2
@@ -1,588 +1,591 @@
 .\" Copyright (c) 1999 Poul-Henning Kamp.
 .\" Copyright (c) 2009 James Gritton.
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd September 9, 2025
+.Dd September 15, 2025
 .Dt JAIL 2
 .Os
 .Sh NAME
 .Nm jail ,
 .Nm jail_get ,
 .Nm jail_set ,
 .Nm jail_remove ,
 .Nm jail_attach ,
 .Nm jail_remove_jd ,
 .Nm jail_attach_jd
 .Nd create and manage system jails
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
 .In sys/param.h
 .In sys/jail.h
 .Ft int
 .Fn jail "struct jail *jail"
 .Ft int
 .Fn jail_attach "int jid"
 .Ft int
 .Fn jail_remove "int jid"
 .Ft int
 .Fn jail_attach_jd "int fd"
 .Ft int
 .Fn jail_remove_jd "int fd"
 .In sys/uio.h
 .Ft int
 .Fn jail_get "struct iovec *iov" "u_int niov" "int flags"
 .Ft int
 .Fn jail_set "struct iovec *iov" "u_int niov" "int flags"
 .Sh DESCRIPTION
 The
 .Fn jail
 system call sets up a jail and locks the current process in it.
 .Pp
 The argument is a pointer to a structure describing the prison:
 .Bd -literal -offset indent
 struct jail {
 	uint32_t	version;
 	char		*path;
 	char		*hostname;
 	char		*jailname;
 	unsigned int	ip4s;
 	unsigned int	ip6s;
 	struct in_addr	*ip4;
 	struct in6_addr	*ip6;
 };
 .Ed
 .Pp
 .Dq Li version
 defines the version of the API in use.
 .Dv JAIL_API_VERSION
 is defined for the current version.
 .Pp
 The
 .Dq Li path
 pointer should be set to the directory which is to be the root of the
 prison.
 .Pp
 The
 .Dq Li hostname
 pointer can be set to the hostname of the prison.
 This can be changed
 from the inside of the prison.
 .Pp
 The
 .Dq Li jailname
 pointer is an optional name that can be assigned to the jail
 for example for management purposes.
 .Pp
 The
 .Dq Li ip4s
 and
 .Dq Li ip6s
 give the numbers of IPv4 and IPv6 addresses that will be passed
 via their respective pointers.
 .Pp
 The
 .Dq Li ip4
 and
 .Dq Li ip6
 pointers can be set to an arrays of IPv4 and IPv6 addresses to be assigned to
 the prison, or NULL if none.
 IPv4 addresses must be in network byte order.
 .Pp
 This is equivalent to, and deprecated in favor of, the
 .Fn jail_set
 system call (see below), with the parameters
 .Va path ,
 .Va host.hostname ,
 .Va name ,
 .Va ip4.addr ,
 and
 .Va ip6.addr ,
 and with the
 .Dv JAIL_ATTACH
 flag.
 .Pp
 The
 .Fn jail_set
 system call creates a new jail, or modifies an existing one, and optionally
 locks the current process in it.
 Jail parameters are passed as an array of name-value pairs in the array
 .Fa iov ,
 containing
 .Fa niov
 elements.
 Parameter names are a null-terminated string, and values may be strings,
 integers, or other arbitrary data.
 Some parameters are boolean, and do not have a value (their length is zero)
 but are set by the name alone with or without a
 .Dq no
 prefix, e.g.
 .Va persist
 or
 .Va nopersist .
 Any parameters not set will be given default values, generally based on
 the current environment.
 .Pp
 Jails have a set of core parameters, and modules can add their own jail
 parameters.
 The current set of available parameters, and their formats, can be
 retrieved via the
 .Va security.jail.param
 sysctl MIB entry.
 Notable parameters include those mentioned in the
 .Fn jail
 description above, as well as
 .Va jid
 and
 .Va name ,
 which identify the jail being created or modified.
 See
 .Xr jail 8
 for more information on the core jail parameters.
 .Pp
 The
 .Fa flags
 arguments consists of one or more of the following flags:
 .Bl -tag -width indent
 .It Dv JAIL_CREATE
 Create a new jail.
 If a
 .Va jid
 or
 .Va name
 parameters exists, they must not refer to an existing jail.
 .It Dv JAIL_UPDATE
 Modify an existing jail.
 One of the
 .Va jid
 or
 .Va name
 parameters must exist, and must refer to an existing jail.
 If both
 .Dv JAIL_CREATE
 and
 .Dv JAIL_UPDATE
 are set, a jail will be created if it does not yet exist, and modified if it
 does exist.
 .It Dv JAIL_ATTACH
 In addition to creating or modifying the jail, attach the current process to
 it, as with the
 .Fn jail_attach
 system call.
 .It Dv JAIL_DYING
 This is deprecated in
 .Fn jail_set
 and has no effect.
 .It Dv JAIL_USE_DESC
 Identify the jail by a descriptor in the
 .Va desc
 parameter.
 .It Dv JAIL_AT_DESC
 Operate in the context of the jail described by the
 .Va desc
 parameter, instead of the current jail.
 Only one of
 .Dv JAIL_USE_DESC
 or
 .Dv JAIL_AT_DESC
 may be specified.
 .It Dv JAIL_GET_DESC
 Return a new jail descriptor for the jail in the
 .Va desc
 parameter.
 .It Dv JAIL_OWN_DESC
 Return an
 .Dq owning
 jail descriptor in the
 .Va desc
 parameter.
 .El
 .Pp
 The
 .Fn jail_get
 system call retrieves jail parameters, using the same name-value list as
 .Fn jail_set
 in the
 .Fa iov
 and
 .Fa niov
 arguments.
 The jail to read can be specified by either
 .Va jid
 or
 .Va name
 by including those parameters in the list.
 If they are included but are not intended to be the search key, they
 should be cleared (zero and the empty string respectively).
 .Pp
 The special parameter
 .Va lastjid
 can be used to retrieve a list of all jails.
 It will fetch the jail with the jid above and closest to the passed value.
 The first jail (usually but not always jid 1) can be found by passing a
 .Va lastjid
 of zero.
 .Pp
 The
 .Fa flags
 arguments consists of one or more following flags:
 .Bl -tag -width indent
 .It Dv JAIL_DYING
 Allow getting a jail that is in the process of being removed.
 .It Dv JAIL_USE_DESC , Dv JAIL_AT_DESC , Dv JAIL_GET_DESC , Dv JAIL_OWN_DESC
 These have the same meaning as they do in
 .Fn jail_set .
 .El
 .Pp
 The
 .Fn jail_attach
 system call attaches the current process to an existing jail,
 identified by
 .Fa jid .
 It changes the process's root and current directories to the jail's
 .Va path
 directory.
 .Pp
 The
 .Fn jail_remove
 system call removes the jail identified by
 .Fa jid .
 It will kill all processes belonging to the jail, and remove any children
 of that jail.
 .Pp
 The
 .Fn jail_attach_fd
 and
 .Fn jail_remove_fd
 system calls work the same as
 .Fn jail_attach
 and
 .Fn jail_remove ,
 except that they operate on the jail identified by jail descriptor
 .Fa fd .
 .Ss Jail Descriptors
 In addition to the jail ID,
 jails can be referred to using a jail descriptor,
 a type of file descriptor tied to a particular jail.
 Jail descriptors are created by calling
 .Fn jail_set
 or
 .Fn jail_get
 with the special parameter
 .Va desc ,
 and either the
 .Dv JAIL_GET_DESC
 or
 .Dv JAIL_OWN_DESC
 flags set.
 The difference between the two flags is that descriptors created with
 .Dv JAIL_OWN_DESC
 .Po
 called
 .Dq owning
 descriptors
 .Pc
 will automatically remove the jail when the descriptor is closed.
 .Pp
 Jail descriptors can be passed back to
 .Fn jail_set
 or
 .Fm jail_get
 with the
 .Va desc
 parameter,
 and either the
 .Dv JAIL_USE_DESC
 or
 .Dv JAIL_AT_DESC
 flags set.
 With
 .Dv JAIL_USE_DESC ,
 the descriptor identifies the jail to operate on,
 instead of the
 .Va jid
 or
 .Va name
 parameter.
 With
 .Dv JAIL_AT_DESC ,
 the descriptor is used in place of the current jail,
 allowing accessing or creating jails that are children of the
 descriptor jail.
 .Pp
 The system calls
 .Fn jail_attach_jd
 and
 .Fn jail_aremove_jd
 work the same as
 .Fn jail_attach
 and
 .Fn jail_remove ,
 except that they operate on the jail referred to by the passed descriptor.
 .Sh RETURN VALUES
 If successful,
 .Fn jail ,
 .Fn jail_set ,
 and
 .Fn jail_get
 return a non-negative integer, termed the jail identifier (JID).
 They return \-1 on failure, and set
 .Va errno
 to indicate the error.
 .Pp
 .Rv -std jail_attach jail_remove jail_attach_jd jail_remove_jd
 .Sh ERRORS
 The
 .Fn jail
 system call
 will fail if:
 .Bl -tag -width Er
 .It Bq Er EPERM
 This process is not allowed to create a jail, either because it is not
 the super-user, or because it would exceed the jail's
 .Va children.max
 limit.
 .It Bq Er EFAULT
 .Fa jail
 points to an address outside the allocated address space of the process.
 .It Bq Er EINVAL
 The version number of the argument is not correct.
 .It Bq Er EAGAIN
 No free JID could be found.
 .El
 .Pp
 The
 .Fn jail_set
 system call
 will fail if:
 .Bl -tag -width Er
 .It Bq Er EPERM
 This process is not allowed to create a jail, either because it is not
 the super-user, or because it would exceed the jail's
 .Va children.max
 limit.
 .It Bq Er EPERM
 The jail descriptor in the
 .Va desc
 parameter was created by a user other than the super-user,
 and the
 .Dv JAIL_USE_DESC
 flag was set.
 .It Bq Er EPERM
 A jail parameter was set to a less restrictive value then the current
 environment.
 .It Bq Er EFAULT
 .Fa Iov ,
 or one of the addresses contained within it,
 points to an address outside the allocated address space of the process.
 .It Bq Er ENOENT
 The jail referred to by a
 .Va jid
 or
 .Va name
 parameter does not exist, and the
 .Dv JAIL_CREATE
 flag is not set.
 .It Bq Er ENOENT
 The jail referred to by a
 .Va jid
 parameter is not accessible by the process, because the process is in a
 different jail.
 .It Bq Er ENOENT
 The jail referred to by a
 .Va desc
 parameter has been removed.
 .It Bq Er EEXIST
 The jail referred to by a
 .Va jid
 or
 .Va name
 parameter exists, and the
 .Dv JAIL_UPDATE
 flag is not set.
 .It Bq Er EINVAL
 A supplied parameter is the wrong size.
 .It Bq Er EINVAL
 A supplied parameter is out of range.
 .It Bq Er EINVAL
 A supplied string parameter is not null-terminated.
 .It Bq Er EINVAL
 A supplied parameter name does not match any known parameters.
 .It Bq Er EINVAL
 One of the
 .Dv JAIL_CREATE
 or
 .Dv JAIL_UPDATE
 flags is not set.
 .It Bq Er ENAMETOOLONG
 A supplied string parameter is longer than allowed.
 .It Bq Er EAGAIN
 There are no jail IDs left.
 .It Bq Er EMFILE
 A jail descriptor could not be created for the
 .Va desc
 parameter with either the
 .Dv JAIL_GET_DESC
 or
 .Dv JAIL_OWN_DESC
 flag set,
 because the process has already reached its limit for open file descriptors.
 .It Bq Er ENFILE
 A jail descriptor could not be created for the
 .Va desc
 parameter with either the
 .Dv JAIL_GET_DESC
 or
 .Dv JAIL_OWN_DESC
 flag set,
 because the system file table is full.
 .El
 .Pp
 The
 .Fn jail_get
 system call
 will fail if:
 .Bl -tag -width Er
 .It Bq Er ENOENT
 The jail referred to by a
 .Va jid
 or
 .Va name
 parameter does not exist.
 .It Bq Er ENOENT
 The jail referred to by a
 .Va jid
 is not accessible by the process, because the process is in a different
 jail.
 .It Bq Er ENOENT
 The
 .Va lastjid
 parameter is greater than the highest current jail ID.
 .It Bq Er ENOENT
 The jail referred to by a
 .Va desc
 parameter has been removed
 .Pq even if the Dv JAIL_CREATE flag has been set .
 .It Bq Er EINVAL
 A supplied parameter is the wrong size.
 .It Bq Er EINVAL
 A supplied parameter is out of range.
 .It Bq Er EINVAL
 A supplied string parameter is not null-terminated.
 .It Bq Er EINVAL
 A supplied parameter name does not match any known parameters.
 .It Bq Er EMFILE
 A jail descriptor could not be created for the
 .Va desc
 parameter with either the
 .Dv JAIL_GET_DESC
 or
 .Dv JAIL_OWN_DESC
 flag set,
 because the process has already reached its limit for open file descriptors.
 .It Bq Er ENFILE
 A jail descriptor could not be created for the
 .Va desc
 parameter with either the
 .Dv JAIL_GET_DESC
 or
 .Dv JAIL_OWN_DESC
 flag set,
 because the system file table is full.
 .El
 .Pp
 The
 .Fn jail_attach
 and
 .Fn jail_remove
 system calls
 will fail if:
 .Bl -tag -width Er
 .It Bq Er EPERM
 A user other than the super-user attempted to attach to or remove a jail.
 .It Bq Er EINVAL
 The jail specified by
 .Fa jid
 does not exist.
 .El
 .Pp
 The
 .Fn jail_attach_jd
 and
 .Fn jail_remove_jd
 system calls
 will fail if:
 .Bl -tag -width Er
 .It Bq Er EINVAL
 The
 .Fa fd
 argument is not a valid jail descriptor.
 .It Bq Er EPERM
 The jail descriptor was created by a user other than the super-user.
 .It Bq Er EINVAL
 The jail specified by
 .Fa jid
 has been removed.
 .El
 .Pp
 Further
 .Fn jail ,
 .Fn jail_set ,
 .Fn jail_attach ,
 and
 .Fn jail_attach_jd
 call
 .Xr chroot 2
 internally, so they can fail for all the same reasons.
+In particular, they return the
+.Bq Er EPERM
+error when the process to join a jail has open directories.
 Please consult the
 .Xr chroot 2
 manual page for details.
 .Sh SEE ALSO
 .Xr chdir 2 ,
 .Xr chroot 2 ,
 .Xr jail 8
 .Sh HISTORY
 The
 .Fn jail
 system call appeared in
 .Fx 4.0 .
 The
 .Fn jail_attach
 system call appeared in
 .Fx 5.1 .
 The
 .Fn jail_set ,
 .Fn jail_get ,
 and
 .Fn jail_remove
 system calls appeared in
 .Fx 8.0 .
 .Sh AUTHORS
 The jail feature was written by
 .An Poul-Henning Kamp
 for R&D Associates
 who contributed it to
 .Fx .
 .An James Gritton
 added the extensible jail parameters and hierarchical jails.