linux-kernel - [PATCH 5/5] idr: Fix idr_alloc

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Message-Id: <20191103114012.30027-7-willy@infradead.org>
Date:   Sun,  3 Nov 2019 03:40:12 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Cong Wang <xiyou.wangcong@...il.com>
Subject: [PATCH 5/5] idr: Fix idr_alloc_u32 on 32-bit systems

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

Attempting to allocate an entry at 0xffffffff when one is already
present would succeed in allocating one at 2^32, which would confuse
everything.  Return -ENOSPC in this case, as expected.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 lib/radix-tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 18c1dfbb1765..c8fa1d274530 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1529,7 +1529,7 @@ void __rcu **idr_get_free(struct radix_tree_root *root,
 			offset = radix_tree_find_next_bit(node, IDR_FREE,
 							offset + 1);
 			start = next_index(start, node, offset);
-			if (start > max)
+			if (start > max || start == 0)
 				return ERR_PTR(-ENOSPC);
 			while (offset == RADIX_TREE_MAP_SIZE) {
 				offset = node->offset + 1;
-- 
2.24.0.rc1