[PATCH 4.14 310/496] mm/vmstat.c: fix vmstat_update() preemption BUG

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Steven J. Hill" <steven.hill@xxxxxxxxxx>

[ Upstream commit c7f26ccfb2c31eb1bf810ba13d044fcf583232db ]

Attempting to hotplug CPUs with CONFIG_VM_EVENT_COUNTERS enabled can
cause vmstat_update() to report a BUG due to preemption not being
disabled around smp_processor_id().

Discovered on Ubiquiti EdgeRouter Pro with Cavium Octeon II processor.

  BUG: using smp_processor_id() in preemptible [00000000] code:
  kworker/1:1/269
  caller is vmstat_update+0x50/0xa0
  CPU: 0 PID: 269 Comm: kworker/1:1 Not tainted
  4.16.0-rc4-Cavium-Octeon-00009-gf83bbd5-dirty #1
  Workqueue: mm_percpu_wq vmstat_update
  Call Trace:
    show_stack+0x94/0x128
    dump_stack+0xa4/0xe0
    check_preemption_disabled+0x118/0x120
    vmstat_update+0x50/0xa0
    process_one_work+0x144/0x348
    worker_thread+0x150/0x4b8
    kthread+0x110/0x140
    ret_from_kernel_thread+0x14/0x1c

Link: http://lkml.kernel.org/r/1520881552-25659-1-git-send-email-steven.hill@xxxxxxxxxx
Signed-off-by: Steven J. Hill <steven.hill@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Tejun Heo <htejun@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/vmstat.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1770,9 +1770,11 @@ static void vmstat_update(struct work_st
 		 * to occur in the future. Keep on running the
 		 * update worker thread.
 		 */
+		preempt_disable();
 		queue_delayed_work_on(smp_processor_id(), mm_percpu_wq,
 				this_cpu_ptr(&vmstat_work),
 				round_jiffies_relative(sysctl_stat_interval));
+		preempt_enable();
 	}
 }