linux-kernel - [PATCH Fix 1/3] maple_tree: Fix mt_destroy_walk() on full non-leaf non-alloc nodes

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Date:   Wed, 15 Jun 2022 14:19:38 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Qian Cai <quic_qiancai@...cinc.com>
CC:     Yu Zhao <yuzhao@...gle.com>
Subject: [PATCH Fix 1/3] maple_tree: Fix mt_destroy_walk() on full non-leaf
 non-alloc nodes

It is possible to iterate over the metadata of full non-leaf nodes when
operating in non-alloc mode.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 lib/maple_tree.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 80622741c6b8..a1035963ae0d 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5429,11 +5429,15 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
 			goto start_slots_free;
 		type = mte_node_type(mas.node);
 		slots = ma_slots(mte_to_node(mas.node), type);
-		if ((offset < mt_slots[type]) && (slots[offset])) {
-			struct maple_enode *parent = mas.node;
+		if ((offset < mt_slots[type])) {
+			struct maple_enode *next = slots[offset];
 
-			mas.node = mas_slot_locked(&mas, slots, offset);
-			slots = mas_destroy_descend(&mas, parent, offset);
+			if (mte_node_type(next) && mte_to_node(next)) {
+				struct maple_enode *parent = mas.node;
+
+				mas.node = mas_slot_locked(&mas, slots, offset);
+				slots = mas_destroy_descend(&mas, parent, offset);
+			}
 		}
 		node = mas_mn(&mas);
 	} while (start != mas.node);
-- 
2.35.1