From: Mike Galbraith <efault@gmx.de>
To: Oleg Nesterov <oleg@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
LKML <linux-kernel@vger.kernel.org>,
Pavel Emelyanov <xemul@parallels.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Louis Rilling <louis.rilling@kerlabs.com>
Subject: [PATCH] Re: [RFC PATCH] namespaces: fix leak on fork() failure
Date: Mon, 30 Apr 2012 05:01:07 +0200 [thread overview]
Message-ID: <1335754867.17899.4.camel@marge.simpson.net> (raw)
In-Reply-To: <20120429165846.GA19054@redhat.com>
On Sun, 2012-04-29 at 18:58 +0200, Oleg Nesterov wrote:
> On 04/29, Eric W. Biederman wrote:
> >
> > Oleg Nesterov <oleg@redhat.com> writes:
> >
> > > Heh. Please look at http://marc.info/?l=linux-kernel&m=127687751003902
> > > and the whole thread, there are a lot more problems here.
> >
> > I don't remember seeing a leak in that conversation.
>
> It was discussed many times ;) in particular, from the link above:
>
> Note: afaics we have another problem. What if copy_process(CLONE_NEWPID)
> fails after pid_ns_prepare_proc() ? Who will do mntput() ?
>
> But we all forgot about this (relatively minor) problem.
>
> > > But this particular one looks simple iirc.
> > >
> > >> @@ -216,6 +216,14 @@ void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
> > >> rcu_assign_pointer(p->nsproxy, new);
> > >>
> > >> if (ns && atomic_dec_and_test(&ns->count)) {
> > >> + /* Handle fork() failure, unmount proc before proceeding */
> > >> + if (unlikely(!new && !((p->flags & PF_EXITING)))) {
> > >> + struct pid_namespace *pid_ns = ns->pid_ns;
> > >> +
> > >> + if (pid_ns && pid_ns != &init_pid_ns)
> > >> + pid_ns_release_proc(pid_ns);
> > >> + }
> > >> +
> > >> /*
> > >> * wait for others to get what they want from this nsproxy.
> > >> *
> > >
> > > At first glance this looks correct. But the PF_EXITING check doesn't
> > > look very nice imho. It is needed to detect the case when the caller
> > > is copy_process()->bad_fork_cleanup_namespaces and p is not current.
> >
> > Mike's proposed change to switch_task_namespace is most definitely not
> > correct. This will potentially get called on unshare
>
> Yes, but please note that this change also checks "new == NULL", so I
> still think the patch is correct.
>
> But,
>
> > > bad_fork_cleanup_namespaces:
> > > + if (unlikely(clone_flags & CLONE_NEWPID))
> > > + pid_ns_release_proc(...);
> > > exit_task_namespaces(p);
> > >
> > >
> > > code into this error path in copy_process?
> >
> > For now Oleg your minimal patch looks good.
>
> Good.
>
> Mike, could you please re-send the patch to akpm? Feel free to add my ack.
> I guess Eric will ack this fix too.
namespaces, pid_ns: fix leakage on fork() failure
Fork() failure post namespace creation for a child cloned with CLONE_NEWPID
leaks pid_namespace/mnt_cache due to proc being mounted during creation, but
not unmounted during cleanup. Call pid_ns_release_proc() during cleanup.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Oleg Nesterov <oleg@redhat.com>
kernel/fork.c | 3 +++
2 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index b9372a0..91482b6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -67,6 +67,7 @@
#include <linux/oom.h>
#include <linux/khugepaged.h>
#include <linux/signalfd.h>
+#include <linux/proc_fs.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1464,6 +1465,8 @@ bad_fork_cleanup_io:
if (p->io_context)
exit_io_context(p);
bad_fork_cleanup_namespaces:
+ if (unlikely(clone_flags & CLONE_NEWPID))
+ pid_ns_release_proc(p->nsproxy->pid_ns);
exit_task_namespaces(p);
bad_fork_cleanup_mm:
if (p->mm)
next prev parent reply other threads:[~2012-04-30 3:01 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-28 9:19 [RFC PATCH] namespaces: fix leak on fork() failure Mike Galbraith
2012-04-28 14:26 ` Oleg Nesterov
2012-04-29 4:13 ` Mike Galbraith
2012-04-29 7:57 ` Eric W. Biederman
2012-04-29 9:49 ` Mike Galbraith
2012-04-29 16:58 ` Oleg Nesterov
2012-04-30 2:59 ` Eric W. Biederman
2012-04-30 3:25 ` Mike Galbraith
2012-05-02 12:40 ` Oleg Nesterov
2012-05-02 17:37 ` Eric W. Biederman
2012-04-30 3:01 ` Mike Galbraith [this message]
[not found] ` <m1zk9rmyh4.fsf@fess.ebiederm.org>
2012-05-01 20:42 ` [PATCH] " Andrew Morton
2012-05-03 3:12 ` Mike Galbraith
2012-05-03 14:56 ` Mike Galbraith
2012-05-04 4:27 ` Mike Galbraith
2012-05-04 7:55 ` Eric W. Biederman
2012-05-04 8:34 ` Mike Galbraith
2012-05-04 9:45 ` Mike Galbraith
2012-05-04 14:13 ` Eric W. Biederman
2012-05-04 14:49 ` Mike Galbraith
2012-05-04 15:36 ` Eric W. Biederman
2012-05-04 16:57 ` Mike Galbraith
2012-05-04 20:29 ` Eric W. Biederman
2012-05-05 5:56 ` Mike Galbraith
2012-05-05 6:08 ` Mike Galbraith
2012-05-05 7:12 ` Mike Galbraith
2012-05-05 11:37 ` Eric W. Biederman
2012-05-07 21:51 ` [PATCH] vfs: Speed up deactivate_super for non-modular filesystems Eric W. Biederman
2012-05-07 22:17 ` Al Viro
2012-05-07 23:56 ` Paul E. McKenney
2012-05-08 1:07 ` Eric W. Biederman
2012-05-08 4:53 ` Mike Galbraith
2012-05-09 7:55 ` Nick Piggin
2012-05-09 11:02 ` Eric W. Biederman
2012-05-15 8:40 ` Nick Piggin
2012-05-16 0:34 ` Eric W. Biederman
2012-05-09 13:59 ` Paul E. McKenney
2012-05-04 8:03 ` [PATCH] Re: [RFC PATCH] namespaces: fix leak on fork() failure Eric W. Biederman
2012-05-04 8:19 ` Mike Galbraith
2012-05-04 8:54 ` Mike Galbraith
2012-05-07 0:32 ` [PATCH 0/3] pidns: Closing the pid namespace exit race Eric W. Biederman
2012-05-07 0:33 ` [PATCH 1/3] pidns: Use task_active_pid_ns in do_notify_parent Eric W. Biederman
2012-05-07 0:35 ` [PATCH 2/3] pidns: Guarantee that the pidns init will be the last pidns process reaped Eric W. Biederman
2012-05-08 22:50 ` Andrew Morton
2012-05-16 18:39 ` Oleg Nesterov
2012-05-16 19:34 ` Oleg Nesterov
2012-05-16 20:54 ` Eric W. Biederman
2012-05-17 17:00 ` Oleg Nesterov
2012-05-17 21:46 ` Eric W. Biederman
2012-05-18 12:39 ` Oleg Nesterov
2012-05-19 0:03 ` Eric W. Biederman
2012-05-21 12:44 ` Oleg Nesterov
2012-05-22 0:16 ` Eric W. Biederman
2012-05-22 0:20 ` [PATCH] pidns: Guarantee that the pidns init will be the last pidns process reaped. v2 Eric W. Biederman
2012-05-22 16:54 ` Oleg Nesterov
2012-05-22 19:23 ` Andrew Morton
2012-05-23 14:52 ` Oleg Nesterov
2012-05-25 15:15 ` [PATCH -mm] pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-r eaped-v2-fix-fix Oleg Nesterov
2012-05-25 15:59 ` [PATCH -mm 0/1] pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper Oleg Nesterov
2012-05-25 16:00 ` [PATCH -mm 1/1] " Oleg Nesterov
2012-05-25 21:43 ` Eric W. Biederman
2012-05-27 19:10 ` [PATCH v2 -mm 0/1] " Oleg Nesterov
2012-05-27 19:11 ` [PATCH v2 -mm 1/1] " Oleg Nesterov
2012-05-29 6:34 ` Eric W. Biederman
2012-05-25 21:25 ` [PATCH -mm] pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-r eaped-v2-fix-fix Eric W. Biederman
2012-05-27 18:41 ` [PATCH -mm v2] " Oleg Nesterov
2012-05-07 0:35 ` [PATCH 3/3] pidns: Make killed children autoreap Eric W. Biederman
2012-05-08 22:51 ` Andrew Morton
2012-04-30 13:57 ` [RFC PATCH] namespaces: fix leak on fork() failure Mike Galbraith
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