linux-kernel - [PATCH 5.15 458/779] mm/mempolicy: fix get

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Message-Id: <20220815180356.852822996@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 20:01:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tianyu Li <tianyu.li@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 458/779] mm/mempolicy: fix get_nodes out of bound access

From: Tianyu Li <tianyu.li@....com>

[ Upstream commit 000eca5d044d1ee23b4ca311793cf3fc528da6c6 ]

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: e130242dc351 ("mm: simplify compat numa syscalls")
Signed-off-by: Tianyu Li <tianyu.li@....com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Mark Rutland <mark.rutland@....com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/mempolicy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9db0158155e1..4472be6f123d 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) {
-- 
2.35.1