linux-kernel - [RFC] nodemask: Consider MAX_NUMNODES inside node

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Message-Id: <20170103082753.25758-1-khandual@linux.vnet.ibm.com>
Date:   Tue,  3 Jan 2017 13:57:53 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     mhocko@...e.com, vbabka@...e.cz, akpm@...ux-foundation.org
Subject: [RFC] nodemask: Consider MAX_NUMNODES inside node_isset

node_isset can give incorrect result if the node number is beyond the
bitmask size (MAX_NUMNODES in this case) which is not checked inside
test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the
node_isset function before calling test_bit.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 include/linux/nodemask.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index 6e66cfd..0aee588b 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -139,7 +139,13 @@ static inline void __nodes_clear(nodemask_t *dstp, unsigned int nbits)
 }
 
 /* No static inline type checking - see Subtlety (1) above. */
-#define node_isset(node, nodemask) test_bit((node), (nodemask).bits)
+#define node_isset(node, nodemask) node_test_bit(node, nodemask, MAX_NUMNODES)
+static inline int node_test_bit(int node, nodemask_t nodemask, int maxnodes)
+{
+	if (node >= maxnodes)
+		return 0;
+	return test_bit((node), (nodemask).bits);
+}
 
 #define node_test_and_set(node, nodemask) \
 			__node_test_and_set((node), &(nodemask))
-- 
1.8.3.1