The branch main has been updated by jamie:
URL:
https://cgit.FreeBSD.org/src/commit/?id=6e1d1bfcac77603541706807803a198c6d954d7c
commit 6e1d1bfcac77603541706807803a198c6d954d7c
Author: Jamie Gritton <ja...@freebsd.org>
AuthorDate: 2021-02-20 22:38:58 +0000
Commit: Jamie Gritton <ja...@freebsd.org>
CommitDate: 2021-02-20 22:38:58 +0000
jail: Improve locking when removing prisons
Change the flow of prison_deref() so it doesn't let go of allprison_lock
until it's completely done using it (except for a possible drop as part
of an upgrade on its first try).
Differential Revision: https://reviews.freebsd.org/D28458
MFC after: 3 days
---
sys/kern/kern_jail.c | 69 +++++++++++++++++++++++++++++++---------------------
1 file changed, 41 insertions(+), 28 deletions(-)
diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c
index 90ab69a372d2..65201eb12951 100644
--- a/sys/kern/kern_jail.c
+++ b/sys/kern/kern_jail.c
@@ -2793,11 +2793,17 @@ prison_complete(void *context, int pending)
static void
prison_deref(struct prison *pr, int flags)
{
- struct prison *ppr, *tpr;
+ struct prisonlist freeprison;
+ struct prison *rpr, *tpr;
int lastref, lasturef;
+ TAILQ_INIT(&freeprison);
if (!(flags & PD_LOCKED))
mtx_lock(&pr->pr_mtx);
+ /*
+ * Release this prison as requested, which may cause its parent
+ * to be released, and then maybe its grandparent, etc.
+ */
for (;;) {
if (flags & PD_DEUREF) {
KASSERT(refcount_load(&pr->pr_uref) > 0,
@@ -2840,56 +2846,63 @@ prison_deref(struct prison *pr, int flags)
mtx_unlock(&pr->pr_mtx);
}
- /* If the prison still has references, nothing else to do. */
- if (!lastref) {
- if (flags & PD_LIST_SLOCKED)
- sx_sunlock(&allprison_lock);
- else if (flags & PD_LIST_XLOCKED)
- sx_xunlock(&allprison_lock);
- return;
- }
+ if (!lastref)
+ break;
if (flags & PD_LIST_SLOCKED) {
if (!sx_try_upgrade(&allprison_lock)) {
sx_sunlock(&allprison_lock);
sx_xlock(&allprison_lock);
}
+ flags &= ~PD_LIST_SLOCKED;
} else if (!(flags & PD_LIST_XLOCKED))
sx_xlock(&allprison_lock);
+ flags |= PD_LIST_XLOCKED;
TAILQ_REMOVE(&allprison, pr, pr_list);
LIST_REMOVE(pr, pr_sibling);
- ppr = pr->pr_parent;
- for (tpr = ppr; tpr != NULL; tpr = tpr->pr_parent)
+ TAILQ_INSERT_TAIL(&freeprison, pr, pr_list);
+ for (tpr = pr->pr_parent; tpr != NULL; tpr = tpr->pr_parent)
tpr->pr_childcount--;
+
+ /* Removing a prison frees a reference on its parent. */
+ pr = pr->pr_parent;
+ mtx_lock(&pr->pr_mtx);
+ flags |= PD_DEREF | PD_DEUREF;
+ }
+
+ /* Release all the prison locks. */
+ if (flags & PD_LIST_SLOCKED)
+ sx_sunlock(&allprison_lock);
+ else if (flags & PD_LIST_XLOCKED)
sx_xunlock(&allprison_lock);
+ /*
+ * Finish removing any unreferenced prisons, which couldn't happen
+ * while allprison_lock was held (to avoid a LOR on vrele).
+ */
+ TAILQ_FOREACH_SAFE(rpr, &freeprison, pr_list, tpr) {
#ifdef VIMAGE
- if (pr->pr_vnet != ppr->pr_vnet)
- vnet_destroy(pr->pr_vnet);
+ if (rpr->pr_vnet != rpr->pr_parent->pr_vnet)
+ vnet_destroy(rpr->pr_vnet);
#endif
- if (pr->pr_root != NULL)
- vrele(pr->pr_root);
- mtx_destroy(&pr->pr_mtx);
+ if (rpr->pr_root != NULL)
+ vrele(rpr->pr_root);
+ mtx_destroy(&rpr->pr_mtx);
#ifdef INET
- free(pr->pr_ip4, M_PRISON);
+ free(rpr->pr_ip4, M_PRISON);
#endif
#ifdef INET6
- free(pr->pr_ip6, M_PRISON);
+ free(rpr->pr_ip6, M_PRISON);
#endif
- if (pr->pr_cpuset != NULL)
- cpuset_rel(pr->pr_cpuset);
- osd_jail_exit(pr);
+ if (rpr->pr_cpuset != NULL)
+ cpuset_rel(rpr->pr_cpuset);
+ osd_jail_exit(rpr);
#ifdef RACCT
if (racct_enable)
- prison_racct_detach(pr);
+ prison_racct_detach(rpr);
#endif
- free(pr, M_PRISON);
-
- /* Removing a prison frees a reference on its parent. */
- pr = ppr;
- mtx_lock(&pr->pr_mtx);
- flags = PD_DEREF | PD_DEUREF;
+ free(rpr, M_PRISON);
}
}
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