Commit 24633953 authored by Jamie Gritton's avatar Jamie Gritton
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MFC jail: Add PD_KILL to remove a prison in prison_deref().

Add the PD_KILL flag that instructs prison_deref() to take steps
to actively kill a prison and its descendents, namely marking it
PRISON_STATE_DYING, clearing its PR_PERSIST flag, and killing any
attached processes.

This replaces a similar loop in sys_jail_remove(), bringing the
operation under the same single hold on allprison_lock that it already
has. It is also used to clean up failed jail (re-)creations in
kern_jail_set(), which didn't generally take all the proper steps.

Differential Revision:  https://reviews.freebsd.org/D28473

(cherry picked from commit 811e27fa)

MFC jail: back out 811e27fa until it doesn't break Jenkins

Reported by:	arichardson

(cherry picked from commit ddfffb41)

MFC jail: re-commit 811e27fa with fixes

Make sure PD_KILL isn't passed to do_jail_attach, where it might end
up trying to kill the caller's prison (even prison0).

Fix the child jail loop in prison_deref_kill, which was doing the
post-order part during the pre-order part.  That's not a system-
killer, but make jails not always die correctly.

(cherry picked from commit c861373b)

MFC jail: Add safety around prison_deref() flags.

do_jail_attach() now only uses the PD_XXX flags that refer to lock
status, so make sure that something else like PD_KILL doesn't slip
through.

Add a KASSERT() in prison_deref() to catch any further PD_KILL misuse.

(cherry picked from commit 589e4c1d)
parent 2bfecbef
......@@ -141,12 +141,13 @@ static int get_next_prid(struct prison **insprp);
static int do_jail_attach(struct thread *td, struct prison *pr, int drflags);
static void prison_complete(void *context, int pending);
static void prison_deref(struct prison *pr, int flags);
static void prison_deref_kill(struct prison *pr, struct prisonlist *freeprison);
static int prison_lock_xlock(struct prison *pr, int flags);
static void prison_free_not_last(struct prison *pr);
static void prison_proc_free_not_last(struct prison *pr);
static void prison_set_allow_locked(struct prison *pr, unsigned flag,
int enable);
static char *prison_path(struct prison *pr1, struct prison *pr2);
static void prison_remove_one(struct prison *pr);
#ifdef RACCT
static void prison_racct_attach(struct prison *pr);
static void prison_racct_modify(struct prison *pr);
......@@ -156,9 +157,12 @@ static void prison_racct_detach(struct prison *pr);
/* Flags for prison_deref */
#define PD_DEREF 0x01 /* Decrement pr_ref */
#define PD_DEUREF 0x02 /* Decrement pr_uref */
#define PD_LOCKED 0x04 /* pr_mtx is held */
#define PD_LIST_SLOCKED 0x08 /* allprison_lock is held shared */
#define PD_LIST_XLOCKED 0x10 /* allprison_lock is held exclusive */
#define PD_KILL 0x04 /* Remove jail, kill processes, etc */
#define PD_LOCKED 0x10 /* pr_mtx is held */
#define PD_LIST_SLOCKED 0x20 /* allprison_lock is held shared */
#define PD_LIST_XLOCKED 0x40 /* allprison_lock is held exclusive */
#define PD_OP_FLAGS 0x07 /* Operation flags */
#define PD_LOCK_FLAGS 0x70 /* Lock status flags */
/*
* Parameter names corresponding to PR_* flag values. Size values are for kvm
......@@ -1756,6 +1760,12 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
pr->pr_flags = (pr->pr_flags & ~ch_flags) | pr_flags;
mtx_unlock(&pr->pr_mtx);
drflags &= ~PD_LOCKED;
/*
* Any errors past this point will need to de-persist newly created
* prisons, as well as call remove methods.
*/
if (born)
drflags |= PD_KILL;
#ifdef RACCT
if (racct_enable && created)
......@@ -1815,17 +1825,12 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
/* Let the modules do their work. */
if (born) {
error = osd_jail_call(pr, PR_METHOD_CREATE, opts);
if (error) {
(void)osd_jail_call(pr, PR_METHOD_REMOVE, NULL);
if (error)
goto done_deref;
}
}
error = osd_jail_call(pr, PR_METHOD_SET, opts);
if (error) {
if (born)
(void)osd_jail_call(pr, PR_METHOD_REMOVE, NULL);
if (error)
goto done_deref;
}
/*
* A new prison is now ready to be seen; either it has gained a user
......@@ -1838,7 +1843,8 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
/* Attach this process to the prison if requested. */
if (flags & JAIL_ATTACH) {
error = do_jail_attach(td, pr, prison_lock_xlock(pr, drflags));
error = do_jail_attach(td, pr,
prison_lock_xlock(pr, drflags & PD_LOCK_FLAGS));
drflags &= ~(PD_LOCKED | PD_LIST_XLOCKED);
if (error) {
vfs_opterror(opts, "attach failed");
......@@ -1860,6 +1866,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
}
#endif
drflags &= ~PD_KILL;
td->td_retval[0] = pr->pr_id;
done_deref:
......@@ -2283,8 +2290,8 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
int
sys_jail_remove(struct thread *td, struct jail_remove_args *uap)
{
struct prison *pr, *cpr, *lpr;
int descend, error;
struct prison *pr;
int error;
error = priv_check(td, PRIV_JAIL_REMOVE);
if (error)
......@@ -2296,90 +2303,16 @@ sys_jail_remove(struct thread *td, struct jail_remove_args *uap)
sx_xunlock(&allprison_lock);
return (EINVAL);
}
/* Remove all descendants of this prison, then remove this prison. */
prison_hold(pr);
if (!LIST_EMPTY(&pr->pr_children)) {
if (!prison_isalive(pr)) {
/* Silently ignore already-dying prisons. */
mtx_unlock(&pr->pr_mtx);
lpr = NULL;
FOREACH_PRISON_DESCENDANT(pr, cpr, descend) {
prison_hold(cpr);
if (lpr != NULL) {
mtx_lock(&lpr->pr_mtx);
prison_remove_one(lpr);
sx_xlock(&allprison_lock);
}
lpr = cpr;
}
if (lpr != NULL) {
mtx_lock(&lpr->pr_mtx);
prison_remove_one(lpr);
sx_xlock(&allprison_lock);
}
mtx_lock(&pr->pr_mtx);
sx_xunlock(&allprison_lock);
return (0);
}
prison_remove_one(pr);
prison_deref(pr, PD_KILL | PD_LOCKED | PD_LIST_XLOCKED);
return (0);
}
static void
prison_remove_one(struct prison *pr)
{
struct proc *p;
int was_alive, drflags;
drflags = PD_DEREF | PD_LOCKED | PD_LIST_XLOCKED;
/*
* Mark the prison as doomed, so it doesn't accidentally come back
* to life. It may still be explicitly brought back by jail_set(2).
*/
was_alive = pr->pr_state == PRISON_STATE_ALIVE;
pr->pr_state = PRISON_STATE_DYING;
/* If the prison was persistent, it is not anymore. */
if (pr->pr_flags & PR_PERSIST) {
drflags |= PD_DEUREF;
prison_free_not_last(pr);
pr->pr_flags &= ~PR_PERSIST;
}
/*
* jail_remove added a reference. If that's the only one, remove
* the prison now. refcount(9) doesn't guarantee the cache coherence
* of non-zero counters, so force it here.
*/
KASSERT(refcount_load(&pr->pr_ref) > 0,
("prison_remove_one removing a dead prison (jid=%d)", pr->pr_id));
if (atomic_load_acq_int(&pr->pr_ref) == 1) {
prison_deref(pr, drflags);
return;
}
/* Tell modules this prison has died. */
mtx_unlock(&pr->pr_mtx);
drflags &= ~PD_LOCKED;
if (was_alive)
(void)osd_jail_call(pr, PR_METHOD_REMOVE, NULL);
sx_xunlock(&allprison_lock);
drflags &= ~PD_LIST_XLOCKED;
/*
* Kill all processes unfortunate enough to be attached to this prison.
*/
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
PROC_LOCK(p);
if (p->p_state != PRS_NEW && p->p_ucred &&
p->p_ucred->cr_prison == pr)
kern_psignal(p, SIGKILL);
PROC_UNLOCK(p);
}
sx_sunlock(&allproc_lock);
/* Remove the temporary reference added by jail_remove. */
prison_deref(pr, drflags);
}
/*
* struct jail_attach_args {
* int jid;
......@@ -2421,6 +2354,7 @@ do_jail_attach(struct thread *td, struct prison *pr, int drflags)
mtx_assert(&pr->pr_mtx, MA_OWNED);
sx_assert(&allprison_lock, SX_LOCKED);
drflags &= PD_LOCK_FLAGS;
/*
* XXX: Note that there is a slight race here if two threads
* in the same privileged process attempt to attach to two
......@@ -2731,6 +2665,24 @@ prison_proc_free(struct prison *pr)
}
}
static void
prison_proc_free_not_last(struct prison *pr)
{
#ifdef INVARIANTS
int lastref;
KASSERT(refcount_load(&pr->pr_uref) > 0,
("Trying to free dead prison %p (jid=%d).",
pr, pr->pr_id));
lastref = refcount_release(&pr->pr_uref);
KASSERT(!lastref,
("prison_proc_free_not_last freed last uref on prison %p (jid=%d).",
pr, pr->pr_id));
#else
refcount_release(&pr->pr_uref);
#endif
}
/*
* Complete a call to either prison_free or prison_proc_free.
*/
......@@ -2764,14 +2716,27 @@ static void
prison_deref(struct prison *pr, int flags)
{
struct prisonlist freeprison;
struct prison *rpr, *ppr, *tpr;
struct prison *killpr, *rpr, *ppr, *tpr;
struct proc *p;
killpr = NULL;
TAILQ_INIT(&freeprison);
/*
* Release this prison as requested, which may cause its parent
* to be released, and then maybe its grandparent, etc.
*/
for (;;) {
if (flags & PD_KILL) {
/* Kill the prison and its descendents. */
KASSERT(pr != &prison0,
("prison_deref trying to kill prison0"));
if (!(flags & PD_DEREF)) {
prison_hold(pr);
flags |= PD_DEREF;
}
flags = prison_lock_xlock(pr, flags);
prison_deref_kill(pr, &freeprison);
}
if (flags & PD_DEUREF) {
/* Drop a user reference. */
KASSERT(refcount_load(&pr->pr_uref) > 0,
......@@ -2800,6 +2765,17 @@ prison_deref(struct prison *pr, int flags)
}
}
}
if (flags & PD_KILL) {
/*
* Any remaining user references are probably processes
* that need to be killed, either in this prison or its
* descendants.
*/
if (refcount_load(&pr->pr_uref) > 0)
killpr = pr;
/* Make sure the parent prison doesn't get killed. */
flags &= ~PD_KILL;
}
if (flags & PD_DEREF) {
/* Drop a reference. */
KASSERT(refcount_load(&pr->pr_ref) > 0,
......@@ -2852,6 +2828,25 @@ prison_deref(struct prison *pr, int flags)
else if (flags & PD_LIST_XLOCKED)
sx_xunlock(&allprison_lock);
/* Kill any processes attached to a killed prison. */
if (killpr != NULL) {
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
PROC_LOCK(p);
if (p->p_state != PRS_NEW && p->p_ucred != NULL) {
for (ppr = p->p_ucred->cr_prison;
ppr != &prison0;
ppr = ppr->pr_parent)
if (ppr == killpr) {
kern_psignal(p, SIGKILL);
break;
}
}
PROC_UNLOCK(p);
}
sx_sunlock(&allproc_lock);
}
/*
* Finish removing any unreferenced prisons, which couldn't happen
* while allprison_lock was held (to avoid a LOR on vrele).
......@@ -2882,6 +2877,91 @@ prison_deref(struct prison *pr, int flags)
}
}
/*
* Kill the prison and its descendants. Mark them as dying, clear the
* persist flag, and call module remove methods.
*/
static void
prison_deref_kill(struct prison *pr, struct prisonlist *freeprison)
{
struct prison *cpr, *ppr, *rpr;
bool descend;
/*
* Unlike the descendants, the target prison can be killed
* even if it is currently dying. This is useful for failed
* creation in jail_set(2).
*/
KASSERT(refcount_load(&pr->pr_ref) > 0,
("Trying to kill dead prison %p (jid=%d).",
pr, pr->pr_id));
refcount_acquire(&pr->pr_uref);
pr->pr_state = PRISON_STATE_DYING;
mtx_unlock(&pr->pr_mtx);
rpr = NULL;
FOREACH_PRISON_DESCENDANT_PRE_POST(pr, cpr, descend) {
if (descend) {
if (!prison_isalive(cpr)) {
descend = false;
continue;
}
prison_hold(cpr);
prison_proc_hold(cpr);
mtx_lock(&cpr->pr_mtx);
cpr->pr_state = PRISON_STATE_DYING;
cpr->pr_flags |= PR_REMOVE;
mtx_unlock(&cpr->pr_mtx);
continue;
}
if (!(cpr->pr_flags & PR_REMOVE))
continue;
(void)osd_jail_call(cpr, PR_METHOD_REMOVE, NULL);
mtx_lock(&cpr->pr_mtx);
cpr->pr_flags &= ~PR_REMOVE;
if (cpr->pr_flags & PR_PERSIST) {
cpr->pr_flags &= ~PR_PERSIST;
prison_proc_free_not_last(cpr);
prison_free_not_last(cpr);
}
(void)refcount_release(&cpr->pr_uref);
if (refcount_release(&cpr->pr_ref)) {
/*
* When the last reference goes, unlink the prison
* and set it aside for prison_deref() to handle.
* Delay unlinking the sibling list to keep the loop
* safe.
*/
if (rpr != NULL)
LIST_REMOVE(rpr, pr_sibling);
rpr = cpr;
rpr->pr_state = PRISON_STATE_INVALID;
TAILQ_REMOVE(&allprison, rpr, pr_list);
TAILQ_INSERT_TAIL(freeprison, rpr, pr_list);
/*
* Removing a prison frees references from its parent.
*/
ppr = rpr->pr_parent;
prison_proc_free_not_last(ppr);
prison_free_not_last(ppr);
for (; ppr != NULL; ppr = ppr->pr_parent)
ppr->pr_childcount--;
}
mtx_unlock(&cpr->pr_mtx);
}
if (rpr != NULL)
LIST_REMOVE(rpr, pr_sibling);
(void)osd_jail_call(pr, PR_METHOD_REMOVE, NULL);
mtx_lock(&pr->pr_mtx);
if (pr->pr_flags & PR_PERSIST) {
pr->pr_flags &= ~PR_PERSIST;
prison_proc_free_not_last(pr);
prison_free_not_last(pr);
}
(void)refcount_release(&pr->pr_uref);
}
/*
* Given the current locking state in the flags, make sure allprison_lock
* is held exclusive, and the prison is locked. Return flags indicating
......
......@@ -341,6 +341,19 @@ prison_unlock(struct prison *pr)
; \
else
/*
* Traverse a prison's descendants, visiting both preorder and postorder.
*/
#define FOREACH_PRISON_DESCENDANT_PRE_POST(ppr, cpr, descend) \
for ((cpr) = (ppr), (descend) = 1; \
((cpr) = (descend) \
? ((descend) = !LIST_EMPTY(&(cpr)->pr_children)) \
? LIST_FIRST(&(cpr)->pr_children) \
: (cpr) \
: ((descend) = LIST_NEXT(cpr, pr_sibling) != NULL) \
? LIST_NEXT(cpr, pr_sibling) \
: cpr->pr_parent) != (ppr);)
/*
* Attributes of the physical system, and the root of the jail tree.
*/
......
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