linux-stable.git/kernel/cgroup/cgroup.c, branch v4.12.2

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

cgroup: fix spurious warnings on cgroup_is_dead() from cgroup_sk_alloc()

2017-04-28T19:28:20+00:00

cgroup_get() expected to be called only on live cgroups and triggers
warning on a dead cgroup; however, cgroup_sk_alloc() may be called
while cloning a socket which is left in an empty and removed cgroup
and thus may legitimately duplicate its reference on a dead cgroup.
This currently triggers the following warning spuriously.

 WARNING: CPU: 14 PID: 0 at kernel/cgroup.c:490 cgroup_get+0x55/0x60
 ...
  [] __warn+0xd3/0xf0
  [] warn_slowpath_null+0x1e/0x20
  [] cgroup_get+0x55/0x60
  [] cgroup_sk_alloc+0x51/0xe0
  [] sk_clone_lock+0x2db/0x390
  [] inet_csk_clone_lock+0x16/0xc0
  [] tcp_create_openreq_child+0x23/0x4b0
  [] tcp_v6_syn_recv_sock+0x91/0x670
  [] tcp_check_req+0x3a6/0x4e0
  [] tcp_v6_rcv+0x693/0xa00
  [] ip6_input_finish+0x59/0x3e0
  [] ip6_input+0x32/0xb0
  [] ip6_rcv_finish+0x57/0xa0
  [] ipv6_rcv+0x318/0x4d0
  [] __netif_receive_skb_core+0x2d7/0x9a0
  [] __netif_receive_skb+0x16/0x70
  [] netif_receive_skb_internal+0x23/0x80
  [] napi_gro_frags+0x208/0x270
  [] mlx4_en_process_rx_cq+0x74c/0xf40
  [] mlx4_en_poll_rx_cq+0x30/0x90
  [] net_rx_action+0x210/0x350
  [] __do_softirq+0x106/0x2c7
  [] irq_exit+0x9d/0xa0 [] do_IRQ+0x54/0xd0
  [] common_interrupt+0x7f/0x7f 
  [] cpuidle_enter+0x17/0x20
  [] cpu_startup_entry+0x2a9/0x2f0
  [] start_secondary+0xf1/0x100

This patch renames the existing cgroup_get() with the dead cgroup
warning to cgroup_get_live() after cgroup_kn_lock_live() and
introduces the new cgroup_get() which doesn't check whether the cgroup
is live or dead.

All existing cgroup_get() users except for cgroup_sk_alloc() are
converted to use cgroup_get_live().

Fixes: d979a39d7242 ("cgroup: duplicate cgroup reference when cloning sockets")
Cc: stable@vger.kernel.org # v4.5+
Cc: Johannes Weiner 
Reported-by: Chris Mason 
Signed-off-by: Tejun Heo

Merge branch 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2017-04-12T06:38:16+00:00

Pull cgroup fixes from Tejun Heo:
 "This contains fixes for two long standing subtle bugs:

   - kthread_bind() on a new kthread binds it to specific CPUs and
     prevents userland from messing with the affinity or cgroup
     membership. Unfortunately, for cgroup membership, there's a window
     between kthread creation and kthread_bind*() invocation where the
     kthread can be moved into a non-root cgroup by userland.

     Depending on what controllers are in effect, this can assign the
     kthread unexpected attributes. For example, in the reported case,
     workqueue workers ended up in a non-root cpuset cgroups and had
     their CPU affinities overridden. This broke workqueue invariants
     and led to workqueue stalls.

     Fixed by closing the window between kthread creation and
     kthread_bind() as suggested by Oleg.

   - There was a bug in cgroup mount path which could allow two
     competing mount attempts to attach the same cgroup_root to two
     different superblocks.

     This was caused by mishandling return value from kernfs_pin_sb().

     Fixed"

* 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: avoid attaching a cgroup root to two different superblocks
  cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups

cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups

2017-03-17T14:18:47+00:00

Creation of a kthread goes through a couple interlocked stages between
the kthread itself and its creator.  Once the new kthread starts
running, it initializes itself and wakes up the creator.  The creator
then can further configure the kthread and then let it start doing its
job by waking it up.

In this configuration-by-creator stage, the creator is the only one
that can wake it up but the kthread is visible to userland.  When
altering the kthread's attributes from userland is allowed, this is
fine; however, for cases where CPU affinity is critical,
kthread_bind() is used to first disable affinity changes from userland
and then set the affinity.  This also prevents the kthread from being
migrated into non-root cgroups as that can affect the CPU affinity and
many other things.

Unfortunately, the cgroup side of protection is racy.  While the
PF_NO_SETAFFINITY flag prevents further migrations, userland can win
the race before the creator sets the flag with kthread_bind() and put
the kthread in a non-root cgroup, which can lead to all sorts of
problems including incorrect CPU affinity and starvation.

This bug got triggered by userland which periodically tries to migrate
all processes in the root cpuset cgroup to a non-root one.  Per-cpu
workqueue workers got caught while being created and ended up with
incorrected CPU affinity breaking concurrency management and sometimes
stalling workqueue execution.

This patch adds task->no_cgroup_migration which disallows the task to
be migrated by userland.  kthreadd starts with the flag set making
every child kthread start in the root cgroup with migration
disallowed.  The flag is cleared after the kthread finishes
initialization by which time PF_NO_SETAFFINITY is set if the kthread
should stay in the root cgroup.

It'd be better to wait for the initialization instead of failing but I
couldn't think of a way of implementing that without adding either a
new PF flag, or sleeping and retrying from waiting side.  Even if
userland depends on changing cgroup membership of a kthread, it either
has to be synchronized with kthread_create() or periodically repeat,
so it's unlikely that this would break anything.

v2: Switch to a simpler implementation using a new task_struct bit
    field suggested by Oleg.

Signed-off-by: Tejun Heo 
Suggested-by: Oleg Nesterov 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Reported-and-debugged-by: Chris Mason 
Cc: stable@vger.kernel.org # v4.3+ (we can't close the race on < v4.3)
Signed-off-by: Tejun Heo

scripts/spelling.txt: add "disble(d)" pattern and fix typo instances

2017-03-10T01:01:09+00:00

Fix typos and add the following to the scripts/spelling.txt:

  disble||disable
  disbled||disabled

I kept the TSL2563_INT_DISBLED in /drivers/iio/light/tsl2563.c
untouched.  The macro is not referenced at all, but this commit is
touching only comment blocks just in case.

Link: http://lkml.kernel.org/r/1481573103-11329-20-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel: convert css_set.refcount from atomic_t to refcount_t

2017-03-08T22:46:03+00:00

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova 
Signed-off-by: Hans Liljestrand 
Signed-off-by: Kees Cook 
Signed-off-by: David Windsor 
Signed-off-by: Tejun Heo

kernel: convert cgroup_namespace.count from atomic_t to refcount_t

2017-03-06T19:55:22+00:00

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova 
Signed-off-by: Hans Liljestrand 
Signed-off-by: Kees Cook 
Signed-off-by: David Windsor 
Signed-off-by: Tejun Heo