git: 811e27fa3c44 - main - jail: Add PD_KILL to remove a prison in prison_deref().
Jamie Gritton
jamie at FreeBSD.org
Mon Feb 22 20:27:57 UTC 2021
The branch main has been updated by jamie:
URL: https://cgit.FreeBSD.org/src/commit/?id=811e27fa3c445664e36071a7d08228fc7fb85676
commit 811e27fa3c445664e36071a7d08228fc7fb85676
Author: Jamie Gritton <jamie at FreeBSD.org>
AuthorDate: 2021-02-22 20:27:44 +0000
Commit: Jamie Gritton <jamie at FreeBSD.org>
CommitDate: 2021-02-22 20:27:44 +0000
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
---
sys/kern/kern_jail.c | 258 ++++++++++++++++++++++++++++++++-------------------
sys/sys/jail.h | 13 +++
2 files changed, 178 insertions(+), 93 deletions(-)
diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c
index 1ddfe3c3df5f..01724e41955c 100644
--- a/sys/kern/kern_jail.c
+++ b/sys/kern/kern_jail.c
@@ -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 +157,10 @@ 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 */
/*
* Parameter names corresponding to PR_* flag values. Size values are for kvm
@@ -1756,6 +1758,12 @@ 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 +1823,12 @@ 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
@@ -1856,6 +1859,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
}
#endif
+ drflags &= ~PD_KILL;
td->td_retval[0] = pr->pr_id;
done_deref:
@@ -2279,8 +2283,8 @@ 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)
@@ -2292,90 +2296,16 @@ 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;
@@ -2727,6 +2657,24 @@ 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.
*/
@@ -2760,14 +2708,25 @@ 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. */
+ 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,
@@ -2796,6 +2755,16 @@ prison_deref(struct prison *pr, int flags)
}
}
}
+ if (flags & PD_KILL) {
+ 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;
+ }
if (flags & PD_DEREF) {
/* Drop a reference. */
KASSERT(refcount_load(&pr->pr_ref) > 0,
@@ -2848,6 +2817,25 @@ 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).
@@ -2878,6 +2866,90 @@ 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);
+ }
+ 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
diff --git a/sys/sys/jail.h b/sys/sys/jail.h
index 723a1fff0b82..c9d4c65e4d9e 100644
--- a/sys/sys/jail.h
+++ b/sys/sys/jail.h
@@ -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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