From 5088ced10c7ed751ffb1adf8076e8d5dfd5752be Mon Sep 17 00:00:00 2001 From: jamie Date: Wed, 15 Jun 2016 01:56:20 +0000 Subject: [PATCH] MFC r301745: Make sure the OSD methods for jail set and remove can't run concurrently, by holding allprison_lock exclusively (even if only for a moment before downgrading) on all paths that call PR_METHOD_REMOVE. Since they may run on a downgraded lock, it's still possible for them to run concurrently with PR_METHOD_GET, which will need to use the prison lock. git-svn-id: svn://svn.freebsd.org/base/stable/10@301907 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f --- sys/kern/kern_jail.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c index 770419ba0..ed2565a80 100644 --- a/sys/kern/kern_jail.c +++ b/sys/kern/kern_jail.c @@ -2400,7 +2400,14 @@ sys_jail_attach(struct thread *td, struct jail_attach_args *uap) if (error) return (error); - sx_slock(&allprison_lock); + /* + * Start with exclusive hold on allprison_lock to ensure that a possible + * PR_METHOD_REMOVE call isn't concurrent with jail_set or jail_remove. + * But then immediately downgrade it since we don't need to stop + * readers. + */ + sx_xlock(&allprison_lock); + sx_downgrade(&allprison_lock); pr = prison_find_child(td->td_ucred->cr_prison, uap->jid); if (pr == NULL) { sx_sunlock(&allprison_lock); @@ -2618,9 +2625,11 @@ prison_complete(void *context, int pending) { struct prison *pr = context; + sx_xlock(&allprison_lock); mtx_lock(&pr->pr_mtx); prison_deref(pr, pr->pr_uref - ? PD_DEREF | PD_DEUREF | PD_LOCKED : PD_LOCKED); + ? PD_DEREF | PD_DEUREF | PD_LOCKED | PD_LIST_XLOCKED + : PD_LOCKED | PD_LIST_XLOCKED); } /* @@ -2664,13 +2673,8 @@ prison_deref(struct prison *pr, int flags) */ if (lasturef) { if (!(flags & (PD_LIST_SLOCKED | PD_LIST_XLOCKED))) { - if (ref > 1) { - sx_slock(&allprison_lock); - flags |= PD_LIST_SLOCKED; - } else { - sx_xlock(&allprison_lock); - flags |= PD_LIST_XLOCKED; - } + sx_xlock(&allprison_lock); + flags |= PD_LIST_XLOCKED; } (void)osd_jail_call(pr, PR_METHOD_REMOVE, NULL); mtx_lock(&pr->pr_mtx); -- 2.45.0