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[PATCH 4.10 25/27] percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages

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

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

From: Tahsin Erdogan <tahsin@google.com>

commit 320661b08dd6f1746d5c7ab4eb435ec64b97cd45 upstream.

Update to pcpu_nr_empty_pop_pages in pcpu_alloc() is currently done
without holding pcpu_lock. This can lead to bad updates to the variable.
Add missing lock calls.

Fixes: b539b87fed37 ("percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated")
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/percpu.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1011,8 +1011,11 @@ area_found:
 		mutex_unlock(&pcpu_alloc_mutex);
 	}
 
-	if (chunk != pcpu_reserved_chunk)
+	if (chunk != pcpu_reserved_chunk) {
+		spin_lock_irqsave(&pcpu_lock, flags);
 		pcpu_nr_empty_pop_pages -= occ_pages;
+		spin_unlock_irqrestore(&pcpu_lock, flags);
+	}
 
 	if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
 		pcpu_schedule_balance_work();

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[PATCH 4.10 00/27] 4.10.6-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:00 +0100
  [PATCH 4.10 10/27] xprtrdma: Squelch kbuild sparse complaint Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:00 +0100
  [PATCH 4.10 14/27] hwrng: omap - write registers after enabling the clock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 12/27] cpufreq: Fix and clean up show_cpuinfo_cur_freq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 11/27] NFS prevent double free in async nfs4_exchange_id Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 15/27] hwrng: omap - use devm_clk_get() instead of of_clk_get() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 06/27] parisc: Fix system shutdown halt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 23/27] isdn/gigaset: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 03/27] qla2xxx: Fix request queue corruption. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 25/27] percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 08/27] perf/core: Fix event inheritance on fork() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 16/27] hwrng: omap - Do not access INTMASK_REG on EIP76 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 17/27] md/raid1/10: fix potential deadlock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 13/27] powerpc/boot: Fix zImage TOC alignment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 04/27] parisc: Optimize flush_kernel_vmap_range and invalidate_kernel_vmap_range Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 09/27] md/r5cache: fix set_syndrome_sources() for data in cache Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 02/27] qla2xxx: Fix memory leak for abts processing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 01/27] give up on gcc ilog2() constant optimizations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 19/27] scsi: lpfc: Add shutdown method for kexec Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.10 05/27] parisc: support R_PARISC_SECREL32 relocation in modules Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.10 07/27] perf/core: Fix use-after-free in perf_release() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.10 22/27] target: Fix VERIFY_16 handling in sbc_parse_cdb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:30 +0100
  [PATCH 4.10 20/27] scsi: libiscsi: add lock around task lists to fix list corruption regression Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:30 +0100
  [PATCH 4.10 18/27] target/pscsi: Fix TYPE_TAPE + TYPE_MEDIMUM_CHANGER export Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:30 +0100
  [PATCH 4.10 21/27] scsi: mpt3sas: Avoid sleeping in interrupt context Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:30 +0100
  [PATCH 4.10 24/27] gfs2: Avoid alignment hole in struct lm_lockname Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:30 +0100
  [PATCH 4.10 26/27] cgroup/pids: remove spurious suspicious RCU usage warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:30 +0100
  Re: [PATCH 4.10 00/27] 4.10.6-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-03-25 01:10 +0100
    Re: [PATCH 4.10 00/27] 4.10.6-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-26 10:30 +0200
  Re: [PATCH 4.10 00/27] 4.10.6-stable review Guenter Roeck <linux@roeck-us.net> - 2017-03-25 05:20 +0100
    Re: [PATCH 4.10 00/27] 4.10.6-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-26 11:10 +0200

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