linux-kernel - [PATCH v2 10/29] radix-tree: Fix sibling entry insertion

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Date:	Thu, 14 Apr 2016 10:16:31 -0400
From:	Matthew Wilcox <willy@...ux.intel.com>
To:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matthew Wilcox <willy@...ux.intel.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Jan Kara <jack@...e.com>, Neil Brown <neilb@...e.de>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: [PATCH v2 10/29] radix-tree: Fix sibling entry insertion

The subtraction was the wrong way round, leading to undefined behaviour
(shift by an amount larger than the size of the type).

Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 lib/radix-tree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 585965a..c0366d1 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -526,8 +526,8 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
 	/* Insert pointers to the canonical entry */
-	if ((shift - order) > 0) {
-		int i, n = 1 << (shift - order);
+	if (order > shift) {
+		int i, n = 1 << (order - shift);
 		offset = offset & ~(n - 1);
 		slot = ptr_to_indirect(&node->slots[offset]);
 		for (i = 0; i < n; i++) {
-- 
2.8.0.rc3