Messages in this thread | | | Date | Thu, 19 Mar 2009 19:07:14 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH 1/1] introduce user_ns inheritance in user-sched |
| |
Quoting Matt Helsley (matthltc@us.ibm.com): > On Thu, Mar 19, 2009 at 04:16:15PM -0500, Serge E. Hallyn wrote: > > In a kernel compiled with CONFIG_USER_SCHED=y, cpu shares are > > allocated according to uid. Shares are specifiable under > > /sys/kernel/uids/<uid>/ > > > > In a kernel compiled with CONFIG_USER_NS=y, clone(2) with the > > CLONE_NEWUSER flag creates a new user namespace, and the newly > > cloned task will belong to uid 0 in the new user namespace. > > > > Without this patch, if uid 500 calls clone(CLONE_NEWUSER) (which > > is possible using a program with the cap_sys_admin,cap_setuid,cap_setgid=pe > > file capabilities), then the new task will get the cpu shares of > > uid 0. > > > > After this patch, if uid 500 calls clone(CLONE_NEWUSER), then even > > though it is uid 0 in the new user namespace, it will be restricted to > > the cpu shares of uid 500. > > > > Currently there is no way to set shares for uids in user namespaces > > other than the initial one. That will be trivial to add when > > sysfs tagging (or its functional equivalent, also needed to > > expose network devices in network namespaces other than init) > > becomes available. > > > > Until cross-user-namespace file accesses are enforced, nothing > > stops uid 0 in a child namespace from simply writing new values > > into /sys/kernel/uids/500. > > > > Here are results of some testing with and without the patch. > > > > Cpu shares are initialized as follows:: > > user root: 2048 > > user hallyn: 1024 > > user serge: 512 > > > > Results are the 'real' part of time make -j4 > o 2>&1, > > each time after a make clean. > > > > ================================================================= > > UNPATCHED > > User 1: user serge creates a child user_ns and runs as user root > > User 2: hallyn runs as user hallyn > > ================================================================= > > User 1 User 2 > > run 1: 2m58.834s 3m0.609s > > run 2: 2m59.248s 2m59.457s > > > > ============================================================= > > PATCHED > > User 1: user serge > > User 2: user hallyn > > ============================================================= > > > > User 1 User 2 > > run 1: 3m6.337s 2m22.681s > > run 2: 3m6.323s 2m21.855s > > > > ============================================================= > > PATCHED > > User 1: user serge setuid to user root > > User 2: hallyn > > ============================================================= > > > > User 1 User 2 > > run 1: 2m17.782s 3m3.947s > > run 2: 2m18.497s 3m7.961s > > > > ========================================================== > > PATCHED > > User 1: user root inside userns created by userid serge > > User 2: hallyn > > ========================================================== > > > > User 1 User 2 > > run 1: 3m9.876s 2m8.428s > > run 2: 3m8.539s 2m6.356s > > > > Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> > > Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com> > > Cc: mingo@elte.hu > > Cc: Bharata B Rao <bharata@linux.vnet.ibm.com> > > Cc: peterz@infradead.org > > --- > > kernel/user.c | 12 +++++++++--- > > kernel/user_namespace.c | 2 +- > > 2 files changed, 10 insertions(+), 4 deletions(-) > > > > diff --git a/kernel/user.c b/kernel/user.c > > index 850e0ba..53aeea2 100644 > > --- a/kernel/user.c > > +++ b/kernel/user.c > > @@ -101,7 +101,12 @@ static int sched_create_user(struct user_struct *up) > > { > > int rc = 0; > > > > - up->tg = sched_create_group(&root_task_group); > > + struct task_group *parent = &root_task_group; > > + > > + if (up->user_ns != &init_user_ns) > > + parent = up->user_ns->creator->tg; > > + > > + up->tg = sched_create_group(parent); > > if (IS_ERR(up->tg)) > > rc = -ENOMEM; > > > > @@ -434,11 +439,11 @@ struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid) > > new->uid = uid; > > atomic_set(&new->__count, 1); > > > > + new->user_ns = get_user_ns(ns); > > + > > if (sched_create_user(new) < 0) > > goto out_free_user; > > > > - new->user_ns = get_user_ns(ns); > > - > > if (uids_user_create(new)) > > goto out_destoy_sched; > > > > @@ -472,6 +477,7 @@ out_destoy_sched: > > sched_destroy_user(new); > > put_user_ns(new->user_ns); > > Shouldn't this put_user_ns(new->user_ns) be removed? It looks like two > references to new->user_ns are being dropped if anything fails > after sched_create_user(new) succeeds yet as far as I can tell the > patch does not introduce any new references to new->user_ns.
Ouch, yeah, thought I'd done that...
Thanks for catching that! Will resend.
> Otherwise looks good to me. > > Cheers, > -Matt Helsley
thanks, -serge
| |