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jail: Add prison_isvalid() and prison_isalive()

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prison_isvalid() checks if a prison record can be used at all, i.e.
pr_ref > 0.  This filters out prisons that aren't fully created, and
those that are either in the process of being dismantled, or will be
at the next opportunity.  While the check for pr_ref > 0 is simple
enough to make without a convenience function, this prepares the way
for other measures of prison validity.

prison_isalive() checks not only validity as far as the useablity of
the prison structure, but also whether the prison is visible to user
space.  It replaces a test for pr_uref > 0, which is currently only
used within kern_jail.c, and not often there.

Both of these functions also assert that either the prison mutex or
allprison_lock is held, since it's generally the case that unlocked
prisons aren't guaranteed to remain useable for any length of time.
This isn't entirely true, for example a thread can assume its own
prison is good, but most exceptions will exist inside of kern_jail.c.
This commit is contained in:
Jamie Gritton 2021-01-18 10:56:20 -08:00
parent efa9c21bca
commit 76ad42abf9
6 changed files with 73 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

94
sys/kern/kern_jail.c
View File

@ -1008,7 +1008,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
TAILQ_FOREACH(inspr, &allprison, pr_list) {
if (inspr->pr_id == jid) {
mtx_lock(&inspr->pr_mtx);
if (inspr->pr_ref > 0) {
if (prison_isvalid(inspr)) {
pr = inspr;
drflags |= PD_LOCKED;
inspr = NULL;
@ -1041,7 +1041,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
error = ENOENT;
vfs_opterror(opts, "jail %d not found", jid);
goto done_deref;
} else if (pr->pr_uref == 0) {
} else if (!prison_isalive(pr)) {
if (!(flags & JAIL_DYING)) {
error = ENOENT;
vfs_opterror(opts, "jail %d is dying",
@ -1118,24 +1118,18 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
FOREACH_PRISON_CHILD(ppr, tpr) {
if (tpr != pr && tpr->pr_ref > 0 &&
!strcmp(tpr->pr_name + pnamelen, namelc)) {
mtx_lock(&tpr->pr_mtx);
drflags |= PD_LOCKED;
if (prison_isalive(tpr)) {
if (pr == NULL &&
cuflags != JAIL_CREATE) {
mtx_lock(&tpr->pr_mtx);
if (tpr->pr_ref > 0) {
/*
* Use this jail
* for updates.
*/
if (tpr->pr_uref > 0) {
pr = tpr;
drflags |=
PD_LOCKED;
break;
}
deadpr = tpr;
}
mtx_unlock(&tpr->pr_mtx);
} else if (tpr->pr_uref > 0) {
/*
* Create, or update(jid):
* name must not exist in an
@ -1147,13 +1141,19 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
name);
goto done_deref;
}
if (pr == NULL &&
cuflags != JAIL_CREATE &&
prison_isvalid(tpr))
deadpr = tpr;
mtx_unlock(&tpr->pr_mtx);
drflags &= ~PD_LOCKED;
}
}
/* If no active jail is found, use a dying one. */
if (deadpr != NULL && pr == NULL) {
if (flags & JAIL_DYING) {
mtx_lock(&deadpr->pr_mtx);
if (deadpr->pr_ref == 0) {
if (!prison_isvalid(deadpr)) {
mtx_unlock(&deadpr->pr_mtx);
goto name_again;
}
@ -1192,7 +1192,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
goto done_deref;
}
mtx_lock(&ppr->pr_mtx);
if (ppr->pr_ref == 0) {
if (!prison_isvalid(ppr)) {
mtx_unlock(&ppr->pr_mtx);
error = ENOENT;
vfs_opterror(opts, "jail \"%s\" not found",
@ -1735,7 +1735,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
* for now, so new ones will remain unseen until after the module
* handlers have completed.
*/
born = pr->pr_uref == 0;
born = !prison_isalive(pr);
if (!created && (ch_flags & PR_PERSIST & (pr_flags ^ pr->pr_flags))) {
if (pr_flags & PR_PERSIST) {
pr->pr_ref++;
@ -2029,8 +2029,8 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
TAILQ_FOREACH(pr, &allprison, pr_list) {
if (pr->pr_id > jid && prison_ischild(mypr, pr)) {
mtx_lock(&pr->pr_mtx);
if (pr->pr_ref > 0 &&
(pr->pr_uref > 0 || (flags & JAIL_DYING)))
if ((flags & JAIL_DYING)
? prison_isvalid(pr) : prison_isalive(pr))
break;
mtx_unlock(&pr->pr_mtx);
}
@ -2051,7 +2051,8 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
pr = prison_find_child(mypr, jid);
if (pr != NULL) {
drflags |= PD_LOCKED;
if (pr->pr_uref == 0 && !(flags & JAIL_DYING)) {
if (!(prison_isalive(pr) ||
(flags & JAIL_DYING))) {
error = ENOENT;
vfs_opterror(opts, "jail %d is dying",
jid);
@ -2075,7 +2076,7 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
pr = prison_find_name(mypr, name);
if (pr != NULL) {
drflags |= PD_LOCKED;
if (pr->pr_uref == 0 && !(flags & JAIL_DYING)) {
if (!(prison_isalive(pr) || (flags & JAIL_DYING))) {
error = ENOENT;
vfs_opterror(opts, "jail \"%s\" is dying",
name);
@ -2203,7 +2204,7 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
if (error != 0 && error != ENOENT)
goto done;
}
i = (pr->pr_uref == 0);
i = !prison_isalive(pr);
error = vfs_setopt(opts, "dying", &i, sizeof(i));
if (error != 0 && error != ENOENT)
goto done;
@ -2314,7 +2315,7 @@ sys_jail_remove(struct thread *td, struct jail_remove_args *uap)
lpr = NULL;
FOREACH_PRISON_DESCENDANT(pr, cpr, descend) {
mtx_lock(&cpr->pr_mtx);
if (cpr->pr_ref > 0) {
if (prison_isvalid(cpr)) {
tpr = cpr;
cpr->pr_ref++;
} else {
@ -2414,11 +2415,8 @@ sys_jail_attach(struct thread *td, struct jail_attach_args *uap)
return (EINVAL);
}
/*
* Do not allow a process to attach to a prison that is not
* considered to be "alive".
*/
if (pr->pr_uref == 0) {
/* Do not allow a process to attach to a prison that is not alive. */
if (!prison_isalive(pr)) {
mtx_unlock(&pr->pr_mtx);
sx_sunlock(&allprison_lock);
return (EINVAL);
@ -2514,7 +2512,7 @@ prison_find(int prid)
TAILQ_FOREACH(pr, &allprison, pr_list) {
if (pr->pr_id == prid) {
mtx_lock(&pr->pr_mtx);
if (pr->pr_ref > 0)
if (prison_isvalid(pr))
return (pr);
/*
* Any active prison with the same ID would have
@ -2542,7 +2540,7 @@ prison_find_child(struct prison *mypr, int prid)
FOREACH_PRISON_DESCENDANT(mypr, pr, descend) {
if (pr->pr_id == prid) {
mtx_lock(&pr->pr_mtx);
if (pr->pr_ref > 0)
if (prison_isvalid(pr))
return (pr);
mtx_unlock(&pr->pr_mtx);
}
@ -2567,18 +2565,17 @@ prison_find_name(struct prison *mypr, const char *name)
FOREACH_PRISON_DESCENDANT(mypr, pr, descend) {
if (!strcmp(pr->pr_name + mylen, name)) {
mtx_lock(&pr->pr_mtx);
if (pr->pr_ref > 0) {
if (pr->pr_uref > 0)
if (prison_isalive(pr))
return (pr);
if (prison_isvalid(pr))
deadpr = pr;
}
mtx_unlock(&pr->pr_mtx);
}
}
/* There was no valid prison - perhaps there was a dying one. */
if (deadpr != NULL) {
mtx_lock(&deadpr->pr_mtx);
if (deadpr->pr_ref == 0) {
if (!prison_isvalid(deadpr)) {
mtx_unlock(&deadpr->pr_mtx);
goto again;
}
@ -2967,6 +2964,37 @@ prison_ischild(struct prison *pr1, struct prison *pr2)
return (0);
}
/*
* Return true if the prison is currently alive. A prison is alive if it is
* valid and it holds user references.
*/
bool
prison_isalive(struct prison *pr)
{
mtx_assert(&pr->pr_mtx, MA_OWNED);
if (__predict_false(pr->pr_ref == 0))
return (false);
if (__predict_false(pr->pr_uref == 0))
return (false);
return (true);
}
/*
* Return true if the prison is currently valid. A prison is valid if it has
* been fully created, and is not being destroyed. Note that dying prisons
* are still considered valid.
*/
bool
prison_isvalid(struct prison *pr)
{
mtx_assert(&pr->pr_mtx, MA_OWNED);
if (__predict_false(pr->pr_ref == 0))
return (false);
return (true);
}
/*
* Return 1 if the passed credential is in a jail and that jail does not
* have its own virtual network stack, otherwise 0.
@ -3623,14 +3651,14 @@ sysctl_jail_list(SYSCTL_HANDLER_ARGS)
cpr->pr_ip6s * sizeof(struct in6_addr));
}
#endif
if (cpr->pr_ref == 0) {
if (!prison_isvalid(cpr)) {
mtx_unlock(&cpr->pr_mtx);
continue;
}
bzero(xp, sizeof(*xp));
xp->pr_version = XPRISON_VERSION;
xp->pr_id = cpr->pr_id;
xp->pr_state = cpr->pr_uref > 0
xp->pr_state = prison_isalive(cpr)
? PRISON_STATE_ALIVE : PRISON_STATE_DYING;
strlcpy(xp->pr_path, prison_path(pr, cpr), sizeof(xp->pr_path));
strlcpy(xp->pr_host, cpr->pr_hostname, sizeof(xp->pr_host));

2
sys/kern/sysv_msg.c
View File

@ -290,7 +290,7 @@ msginit()
if (rsv == NULL)
rsv = osd_reserve(msg_prison_slot);
prison_lock(pr);
if ((pr->pr_allow & PR_ALLOW_SYSVIPC) && pr->pr_ref > 0) {
if (prison_isvalid(pr) && (pr->pr_allow & PR_ALLOW_SYSVIPC)) {
(void)osd_jail_set_reserved(pr, msg_prison_slot, rsv,
&prison0);
rsv = NULL;

2
sys/kern/sysv_sem.c
View File

@ -321,7 +321,7 @@ seminit(void)
if (rsv == NULL)
rsv = osd_reserve(sem_prison_slot);
prison_lock(pr);
if ((pr->pr_allow & PR_ALLOW_SYSVIPC) && pr->pr_ref > 0) {
if (prison_isvalid(pr) && (pr->pr_allow & PR_ALLOW_SYSVIPC)) {
(void)osd_jail_set_reserved(pr, sem_prison_slot, rsv,
&prison0);
rsv = NULL;

2
sys/kern/sysv_shm.c
View File

@ -979,7 +979,7 @@ shminit(void)
if (rsv == NULL)
rsv = osd_reserve(shm_prison_slot);
prison_lock(pr);
if ((pr->pr_allow & PR_ALLOW_SYSVIPC) && pr->pr_ref > 0) {
if (prison_isvalid(pr) && (pr->pr_allow & PR_ALLOW_SYSVIPC)) {
(void)osd_jail_set_reserved(pr, shm_prison_slot, rsv,
&prison0);
rsv = NULL;

3
sys/kern/uipc_mqueue.c
View File

@ -1569,7 +1569,8 @@ mqfs_prison_remove(void *obj, void *data __unused)
found = 0;
TAILQ_FOREACH(tpr, &allprison, pr_list) {
prison_lock(tpr);
if (tpr->pr_root == pr->pr_root && tpr != pr && tpr->pr_ref > 0)
if (tpr != pr && prison_isvalid(tpr) &&
tpr->pr_root == pr->pr_root)
found = 1;
prison_unlock(tpr);
}

2
sys/sys/jail.h
View File

@ -407,6 +407,8 @@ void prison_proc_hold(struct prison *);
void prison_proc_free(struct prison *);
void prison_set_allow(struct ucred *cred, unsigned flag, int enable);
int prison_ischild(struct prison *, struct prison *);
bool prison_isalive(struct prison *);
bool prison_isvalid(struct prison *);
int prison_equal_ip4(struct prison *, struct prison *);
int prison_get_ip4(struct ucred *cred, struct in_addr *ia);
int prison_local_ip4(struct ucred *cred, struct in_addr *ia);