idr: Fix idr_alloc_u32 on 32-bit systems

BugLink: https://bugs.launchpad.net/bugs/1855787
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 434b3270ca4556eb5303021bbaeeaab8544757e6..7c92df492c6fbf7fc9e1fa547be3fbbd49628c2d 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -2180,7 +2180,7 @@ void __rcu **idr_get_free_cmn(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;