From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: [RFC][PATCH 2/2] pidns: Remove proc flush races when a pid namespaces are exiting. Date: Thu, 08 Jul 2010 21:39:59 -0700 Message-ID: References: <20100623203652.GA25298@redhat.com> <1277399329-18087-1-git-send-email-louis.rilling@kerlabs.com> <20100624191843.GA14205@redhat.com> <20100625102303.GG3773@hawkmoon.kerlabs.com> <20100625183733.GA2627@us.ibm.com> <20100625192945.GA25532@redhat.com> <20100625212618.GA11917@us.ibm.com> <20100625212758.GA30474@redhat.com> <20100625220713.GA31123@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: (Eric W. Biederman's message of "Thu\, 08 Jul 2010 21\:36\:32 -0700") Sender: linux-kernel-owner@vger.kernel.org To: Oleg Nesterov Cc: Pavel Emelyanov , Andrew Morton , Linux Containers , linux-kernel@vger.kernel.org, Louis Rilling , Sukadev Bhattiprolu List-Id: containers.vger.kernel.org Currently it is possible to put proc_mnt before we have flushed the last process that will use the proc_mnt to flush it's proc entries. This race is fixed by not flushing proc entries for dead pid namespaces, and calling pid_ns_release_proc unconditionally from zap_pid_ns_processes after the pid namespace has been declared dead. To ensure we don't unnecessarily leak any dcache entries with skipped flushes pid_ns_release_proc flushes the entire proc_mnt when it is called. Signed-off-by: Eric W. Biederman --- fs/proc/base.c | 9 +++++---- fs/proc/root.c | 3 +++ kernel/pid_namespace.c | 1 + 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index acb7ef8..e9d84e1 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2742,13 +2742,14 @@ void proc_flush_task(struct task_struct *task) for (i = 0; i <= pid->level; i++) { upid = &pid->numbers[i]; + + /* Don't bother flushing dead pid namespaces */ + if (test_bit(PIDNS_DEAD, &upid->ns->flags)) + continue; + proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr, tgid->numbers[i].nr); } - - upid = &pid->numbers[pid->level]; - if (upid->nr == 1) - pid_ns_release_proc(upid->ns); } static struct dentry *proc_pid_instantiate(struct inode *dir, diff --git a/fs/proc/root.c b/fs/proc/root.c index cfdf032..2298fdd 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -209,5 +209,8 @@ int pid_ns_prepare_proc(struct pid_namespace *ns) void pid_ns_release_proc(struct pid_namespace *ns) { + /* Flush any cached proc dentries for this pid namespace */ + shrink_dcache_parent(ns->proc_mnt->mnt_root); + mntput(ns->proc_mnt); } diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index 92032d1..43dec5d 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -189,6 +189,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns) rc = sys_wait4(-1, NULL, __WALL, NULL); } while (rc != -ECHILD); + pid_ns_release_proc(pid_ns); acct_exit_ns(pid_ns); return; } -- 1.6.5.2.143.g8cc62