From: Oleg Nesterov <oleg@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Louis Rilling <louis.rilling@kerlabs.com>,
Pavel Emelyanov <xemul@openvz.org>,
Linux Containers <containers@lists.osdl.org>,
linux-kernel@vger.kernel.org,
Daniel Lezcano <dlezcano@fr.ibm.com>
Subject: [PATCH 2/2] pid_ns: refactor the buggy pid_ns_release_proc() logic
Date: Sun, 20 Jun 2010 20:06:37 +0200 [thread overview]
Message-ID: <20100620180637.GD17120@redhat.com> (raw)
In-Reply-To: <20100620180530.GB17120@redhat.com>
pid_namespace holds ns->proc_mnt, while this vfsmount has a referene to
the namespace via PROC_I(sb->s_root->d_inode)->pid. To break this circle
/sbin/init does mntput() in pid_ns_release_proc(). See 6f4e6433.
But we have the following problems:
- Nobody does mntput() if copy_process() fails after
pid_ns_prepare_proc().
- proc_flush_task() checks upid->nr == 1 to verify we are init,
this is wrong if a multi-threaded init does exec.
- As Louis pointed out, this namespace can have the detached
EXIT_DEAD tasks which can use ns->proc_mnt after this mntput().
With this patch only pid_namespace has a reference to ns->proc_mnt, and
mntput(ns->proc_mnt) is called by destroy_pid_namespace() paths when we
know that this ns must not have any references (in particular, there are
no pids in this namespace).
Changes:
- kill proc_flush_task()->pid_ns_release_proc()
- change fs/proc/root.c so that we don't create the "artificial"
references to the namespace or its pid==1.
- change destroy_pid_namespace() to call pid_ns_release_proc().
- change pid_ns_release_proc() to clear s_root->d_inode->pid.
The caller is destroy_pid_namespace(), this pid was already
freed.
Reported-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/pid_namespace.c | 2 ++
fs/proc/base.c | 4 ----
fs/proc/root.c | 10 ++++++----
3 files changed, 8 insertions(+), 8 deletions(-)
--- 35-rc3/kernel/pid_namespace.c~PNS_6_BREAK_CIRCLE 2010-06-20 18:36:00.000000000 +0200
+++ 35-rc3/kernel/pid_namespace.c 2010-06-20 18:50:30.000000000 +0200
@@ -128,6 +128,8 @@ static void destroy_pid_namespace(struct
{
int i;
+ pid_ns_release_proc(ns);
+
for (i = 0; i < PIDMAP_ENTRIES; i++)
kfree(ns->pidmap[i].page);
kmem_cache_free(pid_ns_cachep, ns);
--- 35-rc3/fs/proc/base.c~PNS_6_BREAK_CIRCLE 2010-05-28 13:41:41.000000000 +0200
+++ 35-rc3/fs/proc/base.c 2010-06-20 18:51:14.000000000 +0200
@@ -2745,10 +2745,6 @@ void proc_flush_task(struct task_struct
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,
--- 35-rc3/fs/proc/root.c~PNS_6_BREAK_CIRCLE 2010-06-19 20:11:03.000000000 +0200
+++ 35-rc3/fs/proc/root.c 2010-06-20 18:58:12.000000000 +0200
@@ -31,7 +31,7 @@ static int proc_set_super(struct super_b
struct pid_namespace *ns;
ns = (struct pid_namespace *)data;
- sb->s_fs_info = get_pid_ns(ns);
+ sb->s_fs_info = ns;
return set_anon_super(sb, NULL);
}
@@ -68,7 +68,7 @@ static int proc_get_sb(struct file_syste
struct proc_inode *ei = PROC_I(sb->s_root->d_inode);
if (!ei->pid) {
rcu_read_lock();
- ei->pid = get_pid(find_pid_ns(1, ns));
+ ei->pid = find_pid_ns(1, ns);
rcu_read_unlock();
}
}
@@ -83,7 +83,6 @@ static void proc_kill_sb(struct super_bl
ns = (struct pid_namespace *)sb->s_fs_info;
kill_anon_super(sb);
- put_pid_ns(ns);
}
static struct file_system_type proc_fs_type = {
@@ -209,5 +208,8 @@ int pid_ns_prepare_proc(struct pid_names
void pid_ns_release_proc(struct pid_namespace *ns)
{
- mntput(ns->proc_mnt);
+ if (ns->proc_mnt) {
+ PROC_I(ns->proc_mnt->mnt_sb->s_root->d_inode)->pid = NULL;
+ mntput(ns->proc_mnt);
+ }
}
next prev parent reply other threads:[~2010-06-20 18:08 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-16 16:34 [PATCH] procfs: Do not release pid_ns->proc_mnt too early Louis Rilling
2010-06-17 9:53 ` Pavel Emelyanov
2010-06-17 13:41 ` Eric W. Biederman
2010-06-17 14:20 ` Louis Rilling
2010-06-17 21:36 ` Oleg Nesterov
2010-06-18 8:27 ` Louis Rilling
2010-06-18 16:27 ` Oleg Nesterov
2010-06-21 11:11 ` Louis Rilling
2010-06-21 12:58 ` Eric W. Biederman
2010-06-21 14:15 ` Louis Rilling
2010-06-21 14:26 ` Eric W. Biederman
2010-06-17 21:20 ` Oleg Nesterov
2010-06-18 8:20 ` Louis Rilling
2010-06-18 11:15 ` Oleg Nesterov
2010-06-18 16:08 ` Oleg Nesterov
2010-06-18 17:33 ` Louis Rilling
2010-06-18 17:55 ` Oleg Nesterov
2010-06-18 21:23 ` Oleg Nesterov
2010-06-19 19:08 ` [PATCH 0/4] pid_ns_prepare_proc/unshare cleanups Oleg Nesterov
2010-06-19 19:09 ` [PATCH 1/4] procfs: proc_get_sb: consolidate/cleanup root_inode->pid logic Oleg Nesterov
2010-06-19 19:10 ` [PATCH 2/4] procfs: kill the global proc_mnt variable Oleg Nesterov
2010-06-19 19:10 ` [PATCH 3/4] procfs: move pid_ns_prepare_proc() from copy_process() to create_pid_namespace() Oleg Nesterov
2010-06-19 19:11 ` [PATCH RESEND 4/4] sys_unshare: simplify the not-really-implemented CLONE_THREAD/SIGHAND/VM code Oleg Nesterov
2010-06-20 8:42 ` [PATCH 0/6] Unshare support for the pid namespace Eric W. Biederman
2010-06-20 8:44 ` [PATCH 1/6] pid: Remove the child_reaper special case in init/main.c Eric W. Biederman
2010-06-20 18:29 ` Oleg Nesterov
2010-06-20 20:27 ` Oleg Nesterov
2010-06-20 8:45 ` [PATCH 2/6] pidns: Call pid_ns_prepare_proc from create_pid_namespace Eric W. Biederman
2010-06-20 18:19 ` Oleg Nesterov
2010-06-20 8:45 ` [PATCH 3/6] procfs: kill the global proc_mnt variable Eric W. Biederman
2010-06-20 8:47 ` [PATCH 4/6] pidns: Don't allow new pids after the namespace is dead Eric W. Biederman
2010-06-20 18:44 ` Oleg Nesterov
2010-06-20 8:48 ` [PATCH 5/6] pidns: Use task_active_pid_ns where appropriate Eric W. Biederman
2010-06-20 8:49 ` [PATCH 6/6] pidns: Support unsharing the pid namespace Eric W. Biederman
2010-06-20 20:14 ` Oleg Nesterov
2010-06-20 20:42 ` Oleg Nesterov
2010-06-21 1:53 ` Eric W. Biederman
2010-06-20 18:03 ` [PATCH 0/6] Unshare support for " Oleg Nesterov
2010-06-20 18:05 ` [PATCH 0/2] pid_ns_release_proc() fixes Oleg Nesterov
2010-06-20 18:06 ` [PATCH 1/2] pid_ns: move destroy_pid_namespace() into workqueue context Oleg Nesterov
2010-06-20 18:06 ` Oleg Nesterov [this message]
2010-06-20 21:00 ` [PATCH 0/6] Unshare support for the pid namespace Eric W. Biederman
2010-06-20 21:48 ` Oleg Nesterov
2010-06-20 21:56 ` Oleg Nesterov
2011-01-26 15:57 ` Daniel Lezcano
2010-06-23 20:36 ` [PATCH 0/1] pid_ns: move pid_ns_release_proc() from proc_flush_task() to zap_pid_ns_processes() Oleg Nesterov
2010-06-23 20:37 ` [PATCH 1/1] " Oleg Nesterov
2010-06-24 6:36 ` Sukadev Bhattiprolu
2010-06-24 12:59 ` Oleg Nesterov
2010-06-24 7:06 ` Eric W. Biederman
2010-06-24 13:01 ` Oleg Nesterov
2010-06-24 8:37 ` [PATCH] pid_ns: Fix proc_flush_task() accessing freed proc_mnt Louis Rilling
2010-06-24 17:08 ` [RESEND PATCH] " Louis Rilling
2010-06-24 19:18 ` Oleg Nesterov
2010-06-25 10:23 ` Louis Rilling
2010-06-25 12:21 ` Oleg Nesterov
2010-06-25 18:37 ` Sukadev Bhattiprolu
2010-06-25 19:29 ` Oleg Nesterov
2010-06-25 21:26 ` Sukadev Bhattiprolu
2010-06-25 21:27 ` Oleg Nesterov
2010-06-25 22:07 ` Sukadev Bhattiprolu
2010-07-09 4:36 ` [RFC][PATCH 1/2] pidns: Add a flag to indicate a pid namespace is dead Eric W. Biederman
2010-07-09 4:39 ` [RFC][PATCH 2/2] pidns: Remove proc flush races when a pid namespaces are exiting Eric W. Biederman
2010-07-09 12:14 ` Louis Rilling
2010-07-09 13:05 ` Eric W. Biederman
2010-07-09 14:13 ` Louis Rilling
2010-07-09 15:58 ` [PATCH 01/24] pidns: Remove races by stopping the caching of proc_mnt Eric W. Biederman
2010-07-09 22:13 ` Serge E. Hallyn
2010-07-11 14:14 ` Louis Rilling
2010-07-11 14:25 ` Eric W. Biederman
2010-07-12 18:09 ` [PATCH] pidns: Fix wait for zombies to be reaped in zap_pid_ns_processes Eric W. Biederman
2010-07-13 21:42 ` Louis Rilling
2010-07-13 22:34 ` Serge E. Hallyn
2010-07-14 1:47 ` Eric W. Biederman
2010-10-30 7:07 ` Sukadev Bhattiprolu
2010-07-14 20:53 ` Sukadev Bhattiprolu
2010-07-14 21:35 ` Eric W. Biederman
2010-06-21 11:09 ` [PATCH] procfs: Do not release pid_ns->proc_mnt too early Louis Rilling
2010-06-21 11:15 ` Louis Rilling
2010-06-21 14:38 ` Oleg Nesterov
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