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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 020/321] idr: Fix idr_alloc_u32 on 32-bit systems
Date:   Tue,  3 Dec 2019 23:31:26 +0100
Message-Id: <20191203223428.170816737@linuxfoundation.org>
In-Reply-To: <20191203223427.103571230@linuxfoundation.org>
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From: Matthew Wilcox (Oracle) <willy@infradead.org>

[ Upstream commit b7e9728f3d7fc5c5c8508d99f1675212af5cfd49 ]

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@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 bc03ecc4dfd2f..e5cab5c4e3830 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -2172,7 +2172,7 @@ 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;
-- 
2.20.1