[134/227] hugetlb: clean up potential spectre issue warnings

Commit Message

Andrew Morton March 22, 2022, 9:45 p.m. UTC

From: Mike Kravetz <[e-mail]>
Subject: 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.

The routine cmdline_parse_hugetlb_cma has the same overflow/truncation
issue addressed in [1].  That is also fixed with this change.

[1] https://lore.kernel.org/linux-mm/[e-mail]/

As Michal pointed out, this is unlikely to be exploitable because it is
__init code.  But the patch suppresses the warnings.

[[e-mail]: v2]
  Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Mike Kravetz <[e-mail]>
Cc: Baolin Wang <[e-mail]>
Cc: Zhenguo Yao <[e-mail]>
Cc: Liu Yuntao <[e-mail]>
Cc: Dan Carpenter <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/hugetlb.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Patch

--- a/mm/hugetlb.c~hugetlb-clean-up-potential-spectre-issue-warnings
+++ a/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 *
 			}
 			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_
 			break;
 
 		if (s[count] == ':') {
-			nid = tmp;
-			if (nid < 0 || nid >= MAX_NUMNODES)
+			if (tmp >= MAX_NUMNODES)
 				break;
+			nid = array_index_nospec(tmp, MAX_NUMNODES);
 
 			s += count + 1;
 			tmp = memparse(s, &s);