From: Tianyu Li <tianyu.li@arm.com>
Date: Wed, 1 Jun 2022 09:32:11 +0000 (+0800)
Subject: mm/mempolicy: fix get_nodes out of bound access
X-Git-Tag: baikal/mips/sdk5.9~323
X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=fcbca57cacb586c7b2a26c9813bb16a496c7c67e;p=kernel.git

mm/mempolicy: fix get_nodes out of bound access

[ Upstream commit 01697af165bbe2a3e4ac8f4a985c71b2025f9549 ]

When user specified more nodes than supported, get_nodes will access nmask
array out of bounds.

Link: https://lkml.kernel.org/r/20220601093211.2970565-1-tianyu.li@arm.com
Fixes: 4ed2e8d12f40 ("mm: simplify compat numa syscalls")
Signed-off-by: Tianyu Li <tianyu.li@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9db0158155e1a..4472be6f123db 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1389,7 +1389,7 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
 		unsigned long bits = min_t(unsigned long, maxnode, BITS_PER_LONG);
 		unsigned long t;
 
-		if (get_bitmap(&t, &nmask[maxnode / BITS_PER_LONG], bits))
+		if (get_bitmap(&t, &nmask[(maxnode - 1) / BITS_PER_LONG], bits))
 			return -EFAULT;
 
 		if (maxnode - bits >= MAX_NUMNODES) {