linux-kernel - [PATCH v2 03/44] maple_tree: Reduce user error potential

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Message-ID: <20230105191517.3099082-4-Liam.Howlett@oracle.com>
Date:   Thu, 5 Jan 2023 19:15:53 +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>
CC:     Liam Howlett <liam.howlett@...cle.com>,
        Liam Howlett <liam.howlett@...cle.com>
Subject: [PATCH v2 03/44] maple_tree: Reduce user error potential

From: "Liam R. Howlett" <Liam.Howlett@...cle.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@...cle.com>
---
 lib/maple_tree.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index f3c5ad9ff57f..14cff87cf058 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4742,6 +4742,11 @@ 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;
@@ -4848,6 +4853,11 @@ 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