Add hierarchical jails. A jail may further virtualize its environment

by creating a child jail, which is visible to that jail and to any
parent jails.  Child jails may be restricted more than their parents,
but never less.  Jail names reflect this hierarchy, being MIB-style
dot-separated strings.

Every thread now points to a jail, the default being prison0, which
contains information about the physical system.  Prison0's root
directory is the same as rootvnode; its hostname is the same as the
global hostname, and its securelevel replaces the global securelevel.
Note that the variable "securelevel" has actually gone away, which
should not cause any problems for code that properly uses
securelevel_gt() and securelevel_ge().

Some jail-related permissions that were kept in global variables and
set via sysctls are now per-jail settings.  The sysctls still exist for
backward compatibility, used only by the now-deprecated jail(2) system
call.

Approved by:	bz (mentor)

1 files changed, 5 insertions, 13 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 8c26b131..05d9de5 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -467,22 +467,14 @@ vfs_suser(struct mount *mp, struct thread *td)
 		return (EPERM);
 
 	/*
-	 * If the file system was mounted outside a jail and a jailed thread
-	 * tries to access it, deny immediately.
+	 * If the file system was mounted outside the jail of the calling
+	 * thread, deny immediately.
 	 */
-	if (!jailed(mp->mnt_cred) && jailed(td->td_ucred))
+	if (mp->mnt_cred->cr_prison != td->td_ucred->cr_prison &&
+	    !prison_ischild(td->td_ucred->cr_prison, mp->mnt_cred->cr_prison))
 		return (EPERM);
 
 	/*
-	 * If the file system was mounted inside different jail that the jail of
-	 * the calling thread, deny immediately.
-	 */
-	if (jailed(mp->mnt_cred) && jailed(td->td_ucred) &&
-	    mp->mnt_cred->cr_prison != td->td_ucred->cr_prison) {
-		return (EPERM);
-	}
-
-	/*
 	 * If file system supports delegated administration, we don't check
 	 * for the PRIV_VFS_MOUNT_OWNER privilege - it will be better verified
 	 * by the file system itself.
@@ -2900,7 +2892,7 @@ DB_SHOW_COMMAND(mount, db_show_mount)
 
 	db_printf("    mnt_cred = { uid=%u ruid=%u",
 	    (u_int)mp->mnt_cred->cr_uid, (u_int)mp->mnt_cred->cr_ruid);
-	if (mp->mnt_cred->cr_prison != NULL)
+	if (jailed(mp->mnt_cred))
 		db_printf(", jail=%d", mp->mnt_cred->cr_prison->pr_id);
 	db_printf(" }\n");
 	db_printf("    mnt_ref = %d\n", mp->mnt_ref);