linux-kernel - [RFC] percpu: use nr_groups as check condition

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Date:   Wed, 20 Feb 2019 13:32:55 +0000
From:   Peng Fan <peng.fan@....com>
To:     "dennis@...nel.org" <dennis@...nel.org>,
        "tj@...nel.org" <tj@...nel.org>, "cl@...ux.com" <cl@...ux.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "van.freenix@...il.com" <van.freenix@...il.com>,
        Peng Fan <peng.fan@....com>
Subject: [RFC] percpu: use nr_groups as check condition

group_cnt array is defined with NR_CPUS entries, but normally
nr_groups will not reach up to NR_CPUS. So there is no issue
to the current code.

Checking other parts of pcpu_build_alloc_info, use nr_groups as
check condition, so make it consistent to use 'group < nr_groups'
as for loop check. In case we do have nr_groups equals with NR_CPUS,
we could also avoid memory access out of bounds.

Signed-off-by: Peng Fan <peng.fan@....com>
---
 mm/percpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index db86282fd024..c5c750781628 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -2384,7 +2384,7 @@ static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
 	ai->atom_size = atom_size;
 	ai->alloc_size = alloc_size;
 
-	for (group = 0, unit = 0; group_cnt[group]; group++) {
+	for (group = 0, unit = 0; group < nr_groups; group++) {
 		struct pcpu_group_info *gi = &ai->groups[group];
 
 		/*
-- 
2.16.4