• Roman Gushchin's avatar
    mm: handle no memcg case in memcg_kmem_charge() properly · e68599a3
    Roman Gushchin authored
    Mike Galbraith reported a regression caused by the commit 9b6f7e16
    ("mm: rework memcg kernel stack accounting") on a system with
    "cgroup_disable=memory" boot option: the system panics with the following
    stack trace:
      BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8
      PGD 0 P4D 0
      Oops: 0002 [#1] PREEMPT SMP PTI
      CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410
      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4
      RIP: 0010:page_counter_try_charge+0x22/0xc0
      Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49
      Call Trace:
    The problem occurs because get_mem_cgroup_from_current() returns the NULL
    pointer if memory controller is disabled.  Let's check if this is a case
    at the beginning of memcg_kmem_charge() and just return 0 if
    mem_cgroup_disabled() returns true.  This is how we handle this case in
    many other places in the memory controller code.
    Link: http://lkml.kernel.org/r/20181029215123.17830-1-guro@fb.com
    Fixes: 9b6f7e16 ("mm: rework memcg kernel stack accounting")
    Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
    Reported-by: default avatarMike Galbraith <efault@gmx.de>
    Acked-by: default avatarRik van Riel <riel@surriel.com>
    Acked-by: default avatarMichal Hocko <mhocko@suse.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
    Cc: Shakeel Butt <shakeelb@google.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
memcontrol.c 169 KB