linux-kernel - [PATCH] hugetlb: clean up potential spectre issue warnings

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Date:   Thu, 17 Feb 2022 15:42:18 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Zhenguo Yao <yaozhenguo1@...il.com>,
        Liu Yuntao <liuyuntao10@...wei.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH] hugetlb: clean up potential spectre issue warnings

Recently introduced code allows numa nodes to be specified on the
kernel command line for hugetlb allocations or CMA reservations.  The
node values are user specified and used as indicies into arrays.  This
generated the following smatch warnings:

mm/hugetlb.c:4170 hugepages_setup() warn: potential spectre issue 'default_hugepages_in_node' [w]
mm/hugetlb.c:4172 hugepages_setup() warn: potential spectre issue 'parsed_hstate->max_huge_pages_node' [w]
mm/hugetlb.c:6898 cmdline_parse_hugetlb_cma() warn: potential spectre issue 'hugetlb_cma_size_in_node' [w] (local cap)

Clean up by using array_index_nospec to sanitize array indicies.

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 mm/hugetlb.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1f0cca036f7f..6b14d0791cb4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -31,6 +31,7 @@
 #include <linux/llist.h>
 #include <linux/cma.h>
 #include <linux/migrate.h>
+#include <linux/nospec.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
@@ -4161,7 +4162,7 @@ static int __init hugepages_setup(char *s)
 			}
 			if (tmp >= nr_online_nodes)
 				goto invalid;
-			node = tmp;
+			node = array_index_nospec(tmp, nr_online_nodes);
 			p += count + 1;
 			/* Parse hugepages */
 			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
@@ -6889,9 +6890,9 @@ static int __init cmdline_parse_hugetlb_cma(char *p)
 			break;
 
 		if (s[count] == ':') {
-			nid = tmp;
-			if (nid < 0 || nid >= MAX_NUMNODES)
+			if (tmp < 0 || tmp >= MAX_NUMNODES)
 				break;
+			nid = array_index_nospec(tmp, MAX_NUMNODES);
 
 			s += count + 1;
 			tmp = memparse(s, &s);
-- 
2.34.1