linux-stable.git/kernel/cgroup/cgroup.c, branch v4.13.2

cgroup: fix error return value from cgroup_subtree_control()

2017-07-23T12:15:17+00:00

While refactoring, f7b2814bb9b6 ("cgroup: factor out
cgroup_{apply|finalize}_control() from
cgroup_subtree_control_write()") broke error return value from the
function.  The return value from the last operation is always
overridden to zero.  Fix it.

Signed-off-by: Tejun Heo 
Cc: stable@vger.kernel.org # v4.6+
Signed-off-by: Tejun Heo

cgroup: create dfl_root files on subsys registration

2017-07-18T22:11:43+00:00

On subsystem registration, css_populate_dir() is not called on the new
root css, so the interface files for the subsystem on cgrp_dfl_root
aren't created on registration.  This is a residue from the days when
cgrp_dfl_root was used only as the parking spot for unused subsystems,
which no longer is true as it's used as the root for cgroup2.

This is often fine as later operations tend to create them as a part
of mount (cgroup1) or subtree_control operations (cgroup2); however,
it's not difficult to mount cgroup2 with the controller interface
files missing as Waiman found out.

Fix it by invoking css_populate_dir() on the root css on subsys
registration.

Signed-off-by: Tejun Heo 
Reported-and-tested-by: Waiman Long 
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Tejun Heo

cgroup: don't call migration methods if there are no tasks to migrate

2017-07-08T11:37:50+00:00

Subsystem migration methods shouldn't be called for empty migrations.
cgroup_migrate_execute() implements this guarantee by bailing early if
there are no source css_sets.  This used to be correct before
a79a908fd2b0 ("cgroup: introduce cgroup namespaces"), but no longer
since the commit because css_sets can stay pinned without tasks in
them.

This caused cgroup_migrate_execute() call into cpuset migration
methods with an empty cgroup_taskset.  cpuset migration methods
correctly assume that cgroup_taskset_first() never returns NULL;
however, due to the bug, it can, leading to the following oops.

  Unable to handle kernel paging request for data at address 0x00000960
  Faulting instruction address: 0xc0000000001d6868
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  CPU: 14 PID: 16947 Comm: kworker/14:0 Tainted: G        W
  4.12.0-rc4-next-20170609 #2
  Workqueue: events cpuset_hotplug_workfn
  task: c00000000ca60580 task.stack: c00000000c728000
  NIP: c0000000001d6868 LR: c0000000001d6858 CTR: c0000000001d6810
  REGS: c00000000c72b720 TRAP: 0300   Tainted: GW (4.12.0-rc4-next-20170609)
  MSR: 8000000000009033   CR: 44722422  XER: 20000000
  CFAR: c000000000008710 DAR: 0000000000000960 DSISR: 40000000 SOFTE: 1
  GPR00: c0000000001d6858 c00000000c72b9a0 c000000001536e00 0000000000000000
  GPR04: c00000000c72b9c0 0000000000000000 c00000000c72bad0 c000000766367678
  GPR08: c000000766366d10 c00000000c72b958 c000000001736e00 0000000000000000
  GPR12: c0000000001d6810 c00000000e749300 c000000000123ef8 c000000775af4180
  GPR16: 0000000000000000 0000000000000000 c00000075480e9c0 c00000075480e9e0
  GPR20: c00000075480e8c0 0000000000000001 0000000000000000 c00000000c72ba20
  GPR24: c00000000c72baa0 c00000000c72bac0 c000000001407248 c00000000c72ba20
  GPR28: c00000000141fc80 c00000000c72bac0 c00000000c6bc790 0000000000000000
  NIP [c0000000001d6868] cpuset_can_attach+0x58/0x1b0
  LR [c0000000001d6858] cpuset_can_attach+0x48/0x1b0
  Call Trace:
  [c00000000c72b9a0] [c0000000001d6858] cpuset_can_attach+0x48/0x1b0 (unreliable)
  [c00000000c72ba00] [c0000000001cbe80] cgroup_migrate_execute+0xb0/0x450
  [c00000000c72ba80] [c0000000001d3754] cgroup_transfer_tasks+0x1c4/0x360
  [c00000000c72bba0] [c0000000001d923c] cpuset_hotplug_workfn+0x86c/0xa20
  [c00000000c72bca0] [c00000000011aa44] process_one_work+0x1e4/0x580
  [c00000000c72bd30] [c00000000011ae78] worker_thread+0x98/0x5c0
  [c00000000c72bdc0] [c000000000124058] kthread+0x168/0x1b0
  [c00000000c72be30] [c00000000000b2e8] ret_from_kernel_thread+0x5c/0x74
  Instruction dump:
  f821ffa1 7c7d1b78 60000000 60000000 38810020 7fa3eb78 3f42ffed 4bff4c25
  60000000 3b5a0448 3d420020 eb610020  7f43d378 e9290000 f92af200
  ---[ end trace dcaaf98fb36d9e64 ]---

This patch fixes the bug by adding an explicit nr_tasks counter to
cgroup_taskset and skipping calling the migration methods if the
counter is zero.  While at it, remove the now spurious check on no
source css_sets.

Signed-off-by: Tejun Heo 
Reported-and-tested-by: Abdul Haleem 
Cc: Roman Gushchin 
Cc: stable@vger.kernel.org # v4.6+
Fixes: a79a908fd2b0 ("cgroup: introduce cgroup namespaces")
Link: http://lkml.kernel.org/r/1497266622.15415.39.camel@abdul.in.ibm.com

cgroup: implement "nsdelegate" mount option

2017-06-28T18:45:21+00:00

Currently, cgroup only supports delegation to !root users and cgroup
namespaces don't get any special treatments.  This limits the
usefulness of cgroup namespaces as they by themselves can't be safe
delegation boundaries.  A process inside a cgroup can change the
resource control knobs of the parent in the namespace root and may
move processes in and out of the namespace if cgroups outside its
namespace are visible somehow.

This patch adds a new mount option "nsdelegate" which makes cgroup
namespaces delegation boundaries.  If set, cgroup behaves as if write
permission based delegation took place at namespace boundaries -
writes to the resource control knobs from the namespace root are
denied and migration crossing the namespace boundary aren't allowed
from inside the namespace.

This allows cgroup namespace to function as a delegation boundary by
itself.

v2: Silently ignore nsdelegate specified on !init mounts.

Signed-off-by: Tejun Heo 
Cc: Aravind Anbudurai 
Cc: Serge Hallyn 
Cc: Eric Biederman

cgroup: restructure cgroup_procs_write_permission()

2017-06-28T18:45:02+00:00

Restructure cgroup_procs_write_permission() to make extending
permission logic easier.

This patch doesn't cause any functional changes.

Signed-off-by: Tejun Heo

cgroup: Keep accurate count of tasks in each css_set

2017-06-14T20:01:21+00:00

The reference count in the css_set data structure was used as a
proxy of the number of tasks attached to that css_set. However, that
count is actually not an accurate measure especially with thread mode
support. So a new variable nr_tasks is added to the css_set to keep
track of the actual task count. This new variable is protected by
the css_set_lock. Functions that require the actual task count are
updated to use the new variable.

tj: s/task_count/nr_tasks/ for consistency with cgroup_root->nr_cgrps.
    Refreshed on top of cgroup/for-v4.13 which dropped on
    css_set_populated() -> nr_tasks conversion.

Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo

cgroup: Prevent kill_css() from being called more than once

2017-05-17T20:58:32+00:00

The kill_css() function may be called more than once under the condition
that the css was killed but not physically removed yet followed by the
removal of the cgroup that is hosting the css. This patch prevents any
harmm from being done when that happens.

Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Cc: stable@vger.kernel.org # v4.5+

Merge branch 'for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2017-05-01T20:52:24+00:00

Pull cgroup updates from Tejun Heo:
 "Nothing major. Two notable fixes are Li's second stab at fixing the
  long-standing race condition in the mount path and suppression of
  spurious warning from cgroup_get(). All other changes are trivial"

* 'for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: mark cgroup_get() with __maybe_unused
  cgroup: avoid attaching a cgroup root to two different superblocks, take 2
  cgroup: fix spurious warnings on cgroup_is_dead() from cgroup_sk_alloc()
  cgroup: move cgroup_subsys_state parent field for cache locality
  cpuset: Remove cpuset_update_active_cpus()'s parameter.
  cgroup: switch to BUG_ON()
  cgroup: drop duplicate header nsproxy.h
  kernel: convert css_set.refcount from atomic_t to refcount_t
  kernel: convert cgroup_namespace.count from atomic_t to refcount_t

cgroup: mark cgroup_get() with __maybe_unused

2017-05-01T19:24:14+00:00

a590b90d472f ("cgroup: fix spurious warnings on cgroup_is_dead() from
cgroup_sk_alloc()") converted most cgroup_get() usages to
cgroup_get_live() leaving cgroup_sk_alloc() the sole user of
cgroup_get().  When !CONFIG_SOCK_CGROUP_DATA, this ends up triggering
unused warning for cgroup_get().

Silence the warning by adding __maybe_unused to cgroup_get().

Reported-by: Stephen Rothwell 
Link: http://lkml.kernel.org/r/20170501145340.17e8ef86@canb.auug.org.au
Signed-off-by: Tejun Heo

cgroup: avoid attaching a cgroup root to two different superblocks, take 2

2017-04-28T22:04:54+00:00

Commit bfb0b80db5f9 ("cgroup: avoid attaching a cgroup root to two
different superblocks") is broken.  Now we try to fix the race by
delaying the initialization of cgroup root refcnt until a superblock
has been allocated.

Reported-by: Dmitry Vyukov 
Reported-by: Andrei Vagin 
Tested-by: Andrei Vagin 
Signed-off-by: Zefan Li 
Signed-off-by: Tejun Heo