Re: [PATCH V4 1/8] namespaces: assign each namespace instance a serial number

Richard Guy Briggs
2014-08-21T22:15:01Z

On 14/08/21, Andy Lutomirski wrote:
> On Thu, Aug 21, 2014 at 2:28 PM, Richard Guy Briggs <rgb-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > On 14/08/21, Andy Lutomirski wrote:
> >> On Aug 20, 2014 8:12 PM, "Richard Guy Briggs" <rgb-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> >> >
> >> > Generate and assign a serial number per namespace instance since boot.
> >> >
> >> > Use a serial number per namespace (unique across one boot of one kernel)
> >> > instead of the inode number (which is claimed to have had the right to change
> >> > reserved and is not necessarily unique if there is more than one proc fs) to
> >> > uniquely identify it per kernel boot.
> >> >
> >> > Signed-off-by: Richard Guy Briggs <rgb-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> >> > ---
> >> > fs/mount.h | 1 +
> >> > fs/namespace.c | 1 +
> >> > include/linux/ipc_namespace.h | 1 +
> >> > include/linux/nsproxy.h | 8 ++++++++
> >> > include/linux/pid_namespace.h | 1 +
> >> > include/linux/user_namespace.h | 1 +
> >> > include/linux/utsname.h | 1 +
> >> > include/net/net_namespace.h | 1 +
> >> > init/version.c | 1 +
> >> > ipc/msgutil.c | 1 +
> >> > ipc/namespace.c | 2 ++
> >> > kernel/nsproxy.c | 17 +++++++++++++++++
> >> > kernel/pid.c | 1 +
> >> > kernel/pid_namespace.c | 2 ++
> >> > kernel/user.c | 1 +
> >> > kernel/user_namespace.c | 2 ++
> >> > kernel/utsname.c | 2 ++
> >> > net/core/net_namespace.c | 8 +++++++-
> >> > 18 files changed, 51 insertions(+), 1 deletions(-)
> >> >
> >> > diff --git a/fs/mount.h b/fs/mount.h
> >> > index d55297f..c076f99 100644
> >> > --- a/fs/mount.h
> >> > +++ b/fs/mount.h
> >> > @@ -5,6 +5,7 @@
> >> > struct mnt_namespace {
> >> > atomic_t count;
> >> > unsigned int proc_inum;
> >> > + long long serial_num;
> >> > struct mount * root;
> >> > struct list_head list;
> >> > struct user_namespace *user_ns;
> >> > diff --git a/fs/namespace.c b/fs/namespace.c
> >> > index 182bc41..9af49ff 100644
> >> > --- a/fs/namespace.c
> >> > +++ b/fs/namespace.c
> >> > @@ -2486,6 +2486,7 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
> >> > kfree(new_ns);
> >> > return ERR_PTR(ret);
> >> > }
> >> > + new_ns->serial_num = ns_serial();
> >> > new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
> >> > atomic_set(&new_ns->count, 1);
> >> > new_ns->root = NULL;
> >> > diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
> >> > index 35e7eca..8ccfb2d 100644
> >> > --- a/include/linux/ipc_namespace.h
> >> > +++ b/include/linux/ipc_namespace.h
> >> > @@ -69,6 +69,7 @@ struct ipc_namespace {
> >> > struct user_namespace *user_ns;
> >> >
> >> > unsigned int proc_inum;
> >> > + long long serial_num;
> >> > };
> >> >
> >> > extern struct ipc_namespace init_ipc_ns;
> >> > diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
> >> > index b4ec59d..8e5fe0d 100644
> >> > --- a/include/linux/nsproxy.h
> >> > +++ b/include/linux/nsproxy.h
> >> > @@ -66,6 +66,14 @@ static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
> >> > return rcu_dereference(tsk->nsproxy);
> >> > }
> >> >
> >> > +long long ns_serial(void);
> >> > +enum {
> >> > + NS_IPC_INIT_SN = 1,
> >> > + NS_UTS_INIT_SN = 2,
> >> > + NS_USER_INIT_SN = 3,
> >> > + NS_PID_INIT_SN = 4,
> >>
> >> Please add an extra value here for the first dynamic value...
> >> > +/**
> >> > + * ns_serial - compute a serial number for the namespace
> >> > + *
> >> > + * Compute a serial number for the namespace to uniquely identify it in
> >> > + * audit records.
> >> > + */
> >> > +long long ns_serial(void)
> >> > +{
> >> > + static atomic64_t serial = ATOMIC_INIT(4); /* reserved for IPC, UTS, user, PID */
> >>
> >> ...and use it here.
> >
> > Yup, good idea. Thanks.
> >
> >> Also, does this work on all architectures?
> >
> > I only know for certain x86_64. There is discussion elsewhere about
> > changing ns_serial from returning a long long to returning a u64. That
> > should help. I can run standard compile and boot tests on several
> > others, but won't be able to check output.
>
> I was thinking of atomic64. I guess there's a generic implementation
> that works everywhere, if somewhat slowly.

Yup.

>From include/linux/types.h:
#ifdef CONFIG_64BIT
typedef struct {
long counter;
} atomic64_t;
#endif

>From include/asm-generic/atomic64.h:
typedef struct {
long long counter;
} atomic64_t;

and for non-x86, there is lib/atomic64.c:
atomic64_add_return()
which is in C while the x86_64 version is in ASM.

> --Andy

- RGB

--
Richard Guy Briggs <rbriggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545