From mboxrd@z Thu Jan 1 00:00:00 1970 From: Louis Rilling Subject: Re: [RFC][PATCH 2/2] pidns: Remove proc flush races when a pid namespaces are exiting. Date: Fri, 9 Jul 2010 14:14:25 +0200 Message-ID: <20100709121425.GB18586@hawkmoon.kerlabs.com> References: <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: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=_bohort-1857-1278677591-0001-2" Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Eric W. Biederman" Cc: Oleg Nesterov , Pavel Emelyanov , Andrew Morton , Linux Containers , linux-kernel@vger.kernel.org, Sukadev Bhattiprolu List-Id: containers.vger.kernel.org This is a MIME-formatted message. If you see this text it means that your E-mail software does not support MIME-formatted messages. --=_bohort-1857-1278677591-0001-2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 08/07/10 21:39 -0700, Eric W. Biederman wrote: >=20 > 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. >=20 > 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. One comment below. >=20 > 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. >=20 > 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(-) >=20 > 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) > =20 > for (i =3D 0; i <=3D pid->level; i++) { > upid =3D &pid->numbers[i]; > + > + /* Don't bother flushing dead pid namespaces */ > + if (test_bit(PIDNS_DEAD, &upid->ns->flags)) > + continue; > + IMHO, nothing prevents zap_pid_ns_processes() from setting PIDNS_DEAD and calling pid_ns_release_proc() right now. zap_pid_ns_processes() does not wa= it for EXIT_DEAD (self-reaping) children to be released. Thanks, Louis > proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr, > tgid->numbers[i].nr); > } > - > - upid =3D &pid->numbers[pid->level]; > - if (upid->nr =3D=3D 1) > - pid_ns_release_proc(upid->ns); > } > =20 > 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) > =20 > 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_n= s) > rc =3D sys_wait4(-1, NULL, __WALL, NULL); > } while (rc !=3D -ECHILD); > =20 > + pid_ns_release_proc(pid_ns); > acct_exit_ns(pid_ns); > return; > } > --=20 > 1.6.5.2.143.g8cc62 >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ --=20 Dr Louis Rilling Kerlabs Skype: louis.rilling Batiment Germanium Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes http://www.kerlabs.com/ 35700 Rennes --=_bohort-1857-1278677591-0001-2 Content-Type: application/pgp-signature; name="signature.asc" Content-Transfer-Encoding: 7bit Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkw3EqEACgkQVKcRuvQ9Q1QufQCeMXHzzCwGLKwAKW8ItxR+7IPW nL8Anigv1MNKqViTr8yBfHCKduoEmljI =MuRK -----END PGP SIGNATURE----- --=_bohort-1857-1278677591-0001-2--