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kern_jail.c: Allow mountd/nfsd to optionally run in a jail

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This patch adds "allow.nfsd" to the jail code based on a
new kernel build option VNET_NFSD.  This will not work
until future patches fix nmount(2) to allow mountd to
run in a vnet prison and the NFS server code is patched
so that global variables are in a vnet.

The jail(8) man page will be patched in a future commit.

Reviewed by:	jamie
MFC after:	4 months
Differential Revision:	https://reviews.freebsd.org/D37637
This commit is contained in:
Rick Macklem 2022-12-17 13:43:49 -08:00
parent 38389acc59
commit bba7a2e896
2 changed files with 49 additions and 2 deletions
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47
sys/kern/kern_jail.c
View File

@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_nfs.h"
#include <sys/param.h>
#include <sys/types.h>
@ -218,6 +219,9 @@ static struct bool_flags pr_flag_allow[NBBY * NBPW] = {
{"allow.unprivileged_proc_debug", "allow.nounprivileged_proc_debug",
PR_ALLOW_UNPRIV_DEBUG},
{"allow.suser", "allow.nosuser", PR_ALLOW_SUSER},
#if defined(VNET_NFSD) && defined(VIMAGE) && defined(NFSD)
{"allow.nfsd", "allow.nonfsd", PR_ALLOW_NFSD},
#endif
};
static unsigned pr_allow_all = PR_ALLOW_ALL_STATIC;
const size_t pr_flag_allow_size = sizeof(pr_flag_allow);
@ -2102,6 +2106,13 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
}
#endif
#ifdef VNET_NFSD
if (born && pr != &prison0 && (pr->pr_allow & PR_ALLOW_NFSD) != 0 &&
(pr->pr_root->v_vflag & VV_ROOT) == 0)
printf("Warning jail jid=%d: mountd/nfsd requires a separate"
" file system\n", pr->pr_id);
#endif
drflags &= ~PD_KILL;
td->td_retval[0] = pr->pr_id;
@ -3463,6 +3474,27 @@ prison_check(struct ucred *cred1, struct ucred *cred2)
prison_ischild(cred1->cr_prison, cred2->cr_prison)) ? 0 : ESRCH);
}
/*
* For mountd/nfsd to run within a prison, it must be:
* - A vnet prison.
* - PR_ALLOW_NFSD must be set on it.
* - The root directory (pr_root) of the prison must be
* a file system mount point, so the mountd can hang
* export information on it.
*/
bool
prison_check_nfsd(struct ucred *cred)
{
if (jailed_without_vnet(cred))
return (false);
if (!prison_allow(cred, PR_ALLOW_NFSD))
return (false);
if ((cred->cr_prison->pr_root->v_vflag & VV_ROOT) == 0)
return (false);
return (true);
}
/*
* Return 1 if p2 is a child of p1, otherwise 0.
*/
@ -3717,11 +3749,20 @@ prison_priv_check(struct ucred *cred, int priv)
* is only granted conditionally in the legacy jail case.
*/
switch (priv) {
#ifdef notyet
/*
* NFS-specific privileges.
*/
case PRIV_NFS_DAEMON:
case PRIV_VFS_GETFH:
case PRIV_VFS_MOUNT_EXPORTED:
#ifdef VNET_NFSD
if (!prison_check_nfsd(cred))
#else
printf("running nfsd in a prison requires a kernel "
"built with ''options VNET_NFSD''\n");
#endif
return (EPERM);
#ifdef notyet
case PRIV_NFS_LOCKD:
#endif
/*
@ -4474,6 +4515,10 @@ SYSCTL_JAIL_PARAM(_allow, unprivileged_proc_debug, CTLTYPE_INT | CTLFLAG_RW,
"B", "Unprivileged processes may use process debugging facilities");
SYSCTL_JAIL_PARAM(_allow, suser, CTLTYPE_INT | CTLFLAG_RW,
"B", "Processes in jail with uid 0 have privilege");
#if defined(VNET_NFSD) && defined(VIMAGE) && defined(NFSD)
SYSCTL_JAIL_PARAM(_allow, nfsd, CTLTYPE_INT | CTLFLAG_RW,
"B", "Mountd/nfsd may run in the jail");
#endif
SYSCTL_JAIL_PARAM_SUBNODE(allow, mount, "Jail mount/unmount permission flags");
SYSCTL_JAIL_PARAM(_allow_mount, , CTLTYPE_INT | CTLFLAG_RW,

4
sys/sys/jail.h
View File

@ -253,7 +253,8 @@ struct prison_racct {
#define PR_ALLOW_SUSER 0x00000400
#define PR_ALLOW_RESERVED_PORTS 0x00008000
#define PR_ALLOW_KMEM_ACCESS 0x00010000 /* reserved, not used yet */
#define PR_ALLOW_ALL_STATIC 0x000187ff
#define PR_ALLOW_NFSD 0x00020000
#define PR_ALLOW_ALL_STATIC 0x000387ff
/*
* PR_ALLOW_DIFFERENCES determines which flags are able to be
@ -420,6 +421,7 @@ void getjailname(struct ucred *cred, char *name, size_t len);
void prison0_init(void);
int prison_allow(struct ucred *, unsigned);
int prison_check(struct ucred *cred1, struct ucred *cred2);
bool prison_check_nfsd(struct ucred *cred);
int prison_owns_vnet(struct ucred *);
int prison_canseemount(struct ucred *cred, struct mount *mp);
void prison_enforce_statfs(struct ucred *cred, struct mount *mp,