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From:   "Liam R. Howlett" <Liam.Howlett@oracle.com>
To:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        maple-tree@lists.infradead.org
Cc:     "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
        "Liam R . Howlett" <Liam.Howlett@oracle.com>
Subject: [PATCH v4 03/49] maple_tree: Reduce user error potential
Date:   Fri, 20 Jan 2023 11:26:04 -0500
Message-Id: <20230120162650.984577-4-Liam.Howlett@oracle.com>
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From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

When iterating, a user may operate on the tree and cause the maple state
to be altered and left in an unintuitive state.  Detect this scenario
and correct it by setting to the limit and invalidating the state.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
 lib/maple_tree.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index cbb8bd9b9d25..1af09c6f7810 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4731,6 +4731,11 @@ static inline void *mas_next_entry(struct ma_state *mas, unsigned long limit)
 	unsigned long last;
 	enum maple_type mt;
 
+	if (mas->index > limit) {
+		mas->index = mas->last = limit;
+		mas_pause(mas);
+		return NULL;
+	}
 	last = mas->last;
 retry:
 	offset = mas->offset;
@@ -4837,6 +4842,11 @@ static inline void *mas_prev_entry(struct ma_state *mas, unsigned long min)
 {
 	void *entry;
 
+	if (mas->index < min) {
+		mas->index = mas->last = min;
+		mas_pause(mas);
+		return NULL;
+	}
 retry:
 	while (likely(!mas_is_none(mas))) {
 		entry = mas_prev_nentry(mas, min, mas->index);
-- 
2.35.1