svn commit: r333263 - in head: lib/libjail sys/cddl/contrib/opensolaris/uts/common/fs/zfs sys/compat/linprocfs sys/compat/linsysfs sys/fs/devfs sys/fs/fdescfs sys/fs/nullfs sys/fs/procfs sys/fs/pse...

[James Gritton]

On 2018-11-16 16:30, Alan Somers wrote:

> On Fri, Nov 16, 2018 at 2:28 PM James Gritton <jamie at freebsd.org> wrote: 
> 
> On 2018-11-16 10:34, Alan Somers wrote: 
> 
> On Fri, May 4, 2018 at 2:54 PM Jamie Gritton <jamie at freebsd.org> wrote: 
> Author: jamie
> Date: Fri May  4 20:54:27 2018
> New Revision: 333263
> URL: https://svnweb.freebsd.org/changeset/base/333263
> 
> Log:
> Make it easier for filesystems to count themselves as jail-enabled,
> by doing most of the work in a new function prison_add_vfs in kern_jail.c
> Now a jail-enabled filesystem need only mark itself with VFCF_JAIL, and
> the rest is taken care of.  This includes adding a jail parameter like
> allow.mount.foofs, and a sysctl like security.jail.mount_foofs_allowed.
> Both of these used to be a static list of known filesystems, with
> predefined permission bits.
> 
> Reviewed by:  kib
> Differential Revision:        D14681
> 
> Modified:
> head/lib/libjail/jail.c
> head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
> head/sys/compat/linprocfs/linprocfs.c
> head/sys/compat/linsysfs/linsysfs.c
> head/sys/fs/devfs/devfs_vfsops.c
> head/sys/fs/fdescfs/fdesc_vfsops.c
> head/sys/fs/nullfs/null_vfsops.c
> head/sys/fs/procfs/procfs.c
> head/sys/fs/pseudofs/pseudofs.h
> head/sys/fs/tmpfs/tmpfs_vfsops.c
> head/sys/kern/kern_jail.c
> head/sys/kern/vfs_init.c
> head/sys/kern/vfs_mount.c
> head/sys/kern/vfs_subr.c
> head/sys/sys/jail.h
> head/sys/sys/mount.h
> head/usr.sbin/jail/jail.8
> 
> Modified: head/lib/libjail/jail.c
> ==============================================================================
> --- head/lib/libjail/jail.c     Fri May  4 20:38:26 2018        (r333262)
> +++ head/lib/libjail/jail.c     Fri May  4 20:54:27 2018        (r333263)
> @@ -1048,7 +1048,13 @@ kldload_param(const char *name)
> else if (strcmp(name, "sysvmsg") == 0 || strcmp(name, "sysvsem") == 0 ||
> strcmp(name, "sysvshm") == 0)
> kl = kldload(name);
> -       else {
> +       else if (strncmp(name, "allow.mount.", 12) == 0) {
> +               /* Load the matching filesystem */
> +               kl = kldload(name + 12);
> +               if (kl < 0 && errno == ENOENT &&
> +                   strncmp(name + 12, "no", 2) == 0)
> +                       kl = kldload(name + 14);
> +       } else {
> errno = ENOENT;
> return (-1);
> } 
> I'm curious about this part of the change.  Why is it necessary to load the module in the "allow.mount.noXXXfs" case, when the jail is forbidden to mount the filesystem? It seems like that would just load modules that aren't going to be used. 
> Additional discussion at https://github.com/iocage/iocage/issues/689 . 
> -Alan

Presumably such a parameter would be included in some jails in
conjunction with the positive being included in others (perhaps as a
default).  The truth is I never really considered whether the "no"
option would be used, I just always treat these option as pairs. 
It may be reasonable (at least in the allow.mount.* case) to silently
disregard a "no" option that doesn't exist, but I don't know how many
places would need to be modified for that to go smoothly.  Though I
don't expect that there would be too many people who bother to include a
jail parameter about a filesystem which they're not planning to use. 
- Jamie 

Well, many people use the "no" option because one of the most popular
jail managers, iocage, uses it under the hood.  But since "no" is the
default, its presence on the command line is a noop.  Are there any
situations in which the "no" option has an effect?  The only two
possibilities I could think of were: 

1) Somebody puts both the positive and negative options on the same
command line.  From experiment, it seems like the last option takes
effect.  In this case, the presence of the positive option would cause
the kld to be loaded, regardless of the presence of the negative option.

2) When using hierarchical jails, it might make sense to use the
positive option for the outer jail and the negative option for the inner
jail.  But this would only be important if the inner jail inherited the
outer jail's parameters, which doesn't seem to be the case. 

So I can't think of any reason to continue to mount the kld for "no"
options.  Can you? 

3) There's allow.mount.foofs as a global parameter, with some jails
overriding that with a jail-specific allow.mount.nofoofs.  In that case,
KLD loading shouldn't be a problem as global parameters typically come
first. 

It makes sense not to load a KLD for a "no" option, as long as that
option is then silently ignored.  I wouldn't want it to error out with
"unknown parameter".