From: Tahsin Erdogan <tahsin@google.com>
Date: Sat, 25 Feb 2017 21:00:19 +0000 (-0800)
Subject: percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages
X-Git-Tag: v4.9.18~4
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3f406ecddf8a8d4b6c2de195336ae1c6b56722c1;p=users%2Fdwmw2%2Flinux.git

percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages

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>
---

diff --git a/mm/percpu.c b/mm/percpu.c
index 2557143023941..f014cebbf4054 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1010,8 +1010,11 @@ 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();