ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes:
> Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:
>
>> On Wed, 16 Sep 2015 12:58:04 -0700 bsegall@xxxxxxxxxx wrote:
>>
>>> setpriority(PRIO_USER, 0, x) will change the priority of tasks outside
>>> of the current pid namespace. This is in contrast to both the other
>>> modes of setpriority and the example of kill(-1). Fix this. getpriority
>>> and ioprio have the same failure mode, fix them too.
>>
>> (cc Eric)
> (cc Containers)
>
> Interesting. Strictly speaking the current behavior is not wrong.
> Searching for all threads with a given uid has nothing to do with pids
> so the pid namespace not limiting them is natural.
>
> In practice I don't think anyone cares either way (except people with
> one color or another of security hat on) so this might be a change we
> can actually make.
>
> In general it is probably better not to share uids and gids between
> containers.
>
> Ben do you have a use case where this actually matters? Or was this a
> case of "That looks wrong..."?
>
> Eric
I believe we generally want this for isolation of a process, without
requiring root initially (and a non-trivial uid_map, not to mention
creating the extra users, requires root). There are probably other holes
in using namespaces like this, but are they intended?
(Cc the relevant team member at google)
>
>>> Signed-off-by: Ben Segall <bsegall@xxxxxxxxxx>
>>> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
>>> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
>>> ---
>>> block/ioprio.c | 6 ++++--
>>> kernel/sys.c | 4 ++--
>>> 2 files changed, 6 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/block/ioprio.c b/block/ioprio.c
>>> index 31666c9..cc7800e 100644
>>> --- a/block/ioprio.c
>>> +++ b/block/ioprio.c
>>> @@ -123,7 +123,8 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
>>> break;
>>>
>>> do_each_thread(g, p) {
>>> - if (!uid_eq(task_uid(p), uid))
>>> + if (!uid_eq(task_uid(p), uid) ||
>>> + !task_pid_vnr(p))
>>> continue;
>>> ret = set_task_ioprio(p, ioprio);
>>> if (ret)
>>> @@ -220,7 +221,8 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
>>> break;
>>>
>>> do_each_thread(g, p) {
>>> - if (!uid_eq(task_uid(p), user->uid))
>>> + if (!uid_eq(task_uid(p), user->uid) ||
>>> + !task_pid_vnr(p))
>>> continue;
>>> tmpio = get_task_ioprio(p);
>>> if (tmpio < 0)
>>> diff --git a/kernel/sys.c b/kernel/sys.c
>>> index fa2f2f6..6af9212 100644
>>> --- a/kernel/sys.c
>>> +++ b/kernel/sys.c
>>> @@ -222,7 +222,7 @@ SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)
>>> goto out_unlock; /* No processes for this user */
>>> }
>>> do_each_thread(g, p) {
>>> - if (uid_eq(task_uid(p), uid))
>>> + if (uid_eq(task_uid(p), uid) && task_pid_vnr(p))
>>> error = set_one_prio(p, niceval, error);
>>> } while_each_thread(g, p);
>>> if (!uid_eq(uid, cred->uid))
>>> @@ -290,7 +290,7 @@ SYSCALL_DEFINE2(getpriority, int, which, int, who)
>>> goto out_unlock; /* No processes for this user */
>>> }
>>> do_each_thread(g, p) {
>>> - if (uid_eq(task_uid(p), uid)) {
>>> + if (uid_eq(task_uid(p), uid) && task_pid_vnr(p)) {
>>> niceval = nice_to_rlimit(task_nice(p));
>>> if (niceval > retval)
>>> retval = niceval;
>>> --
>>> 2.6.0.rc0.131.gf624c3d
>>>
>>> --
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