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3868314882
linux/kernel/cgroup
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Tejun Heo 3868314882 cgroup: statically initialize init_css_set->dfl_cgrp 
Like other csets, init_css_set's dfl_cgrp is initialized when the cset
gets linked.  init_css_set gets linked in cgroup_init().  This has
been fine till now but the recently added basic CPU usage accounting
may end up accessing dfl_cgrp of init before cgroup_init() leading to
the following oops.

  SELinux:  Initializing.
  BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
  IP: account_system_index_time+0x60/0x90
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc2-00003-g041cd64 #10
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
  +1.9.3-20161025_171302-gandalf 04/01/2014
  task: ffffffff81e10480 task.stack: ffffffff81e00000
  RIP: 0010:account_system_index_time+0x60/0x90
  RSP: 0000:ffff880011e03cb8 EFLAGS: 00010002
  RAX: ffffffff81ef8800 RBX: ffffffff81e10480 RCX: 0000000000000003
  RDX: 0000000000000000 RSI: 00000000000f4240 RDI: 0000000000000000
  RBP: ffff880011e03cc0 R08: 0000000000010000 R09: 0000000000000000
  R10: 0000000000000020 R11: 0000003b9aca0000 R12: 000000000001c100
  R13: 0000000000000000 R14: ffffffff81e10480 R15: ffffffff81e03cd8
  FS:  0000000000000000(0000) GS:ffff880011e00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000000000b0 CR3: 0000000001e09000 CR4: 00000000000006b0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   <IRQ>
   account_system_time+0x45/0x60
   account_process_tick+0x5a/0x140
   update_process_times+0x22/0x60
   tick_periodic+0x2b/0x90
   tick_handle_periodic+0x25/0x70
   timer_interrupt+0x15/0x20
   __handle_irq_event_percpu+0x7e/0x1b0
   handle_irq_event_percpu+0x23/0x60
   handle_irq_event+0x42/0x70
   handle_level_irq+0x83/0x100
   handle_irq+0x6f/0x110
   do_IRQ+0x46/0xd0
   common_interrupt+0x9d/0x9d

Fix it by statically initializing init_css_set.dfl_cgrp so that init's
default cgroup is accessible from the get-go.

Fixes: 041cd640b2 ("cgroup: Implement cgroup2 basic CPU usage accounting")
Reported-by: “kbuild-all@01.org” <kbuild-all@01.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2017-09-25 14:02:53 -07:00
..
cgroup-internal.h cgroup: Implement cgroup2 basic CPU usage accounting 2017-09-25 08:12:05 -07:00
cgroup-v1.c cgroup: Add mount flag to enable cpuset to use v2 behavior in v1 cgroup 2017-08-18 08:24:21 -07:00
cgroup.c cgroup: statically initialize init_css_set->dfl_cgrp 2017-09-25 14:02:53 -07:00
cpuset.c Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-12 11:30:56 -07:00
debug.c cgroup: update debug controller to print out thread mode information 2017-07-21 11:14:51 -04:00
freezer.c cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS 2017-07-21 11:14:51 -04:00
Makefile cgroup: Implement cgroup2 basic CPU usage accounting 2017-09-25 08:12:05 -07:00
namespace.c kernel: convert cgroup_namespace.count from atomic_t to refcount_t 2017-03-06 14:55:22 -05:00
pids.c cgroup: implement cgroup v2 thread support 2017-07-21 11:14:51 -04:00
rdma.c
stat.c cgroup: Implement cgroup2 basic CPU usage accounting 2017-09-25 08:12:05 -07:00