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

Andy Lutomirski
2014-08-21T21:30:25Z

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.

--Andy