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Message-ID: <20240820175417.2782532-1-Liam.Howlett@oracle.com>
Date: Tue, 20 Aug 2024 13:54:17 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: maple-tree@...ts.infradead.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
syzbot+036af2f0c7338a33b0cd@...kaller.appspotmail.com
Subject: [PATCH] maple_tree: Remove rcu_read_lock() from mt_validate()
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
The write lock should be held when validating the tree to avoid updates
racing with checks. Holding the rcu read lock during a large tree
validation may also cause a prolonged rcu read window.
Link: https://lore.kernel.org/all/0000000000001d12d4062005aea1@google.com/
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
Reported-by: syzbot+036af2f0c7338a33b0cd@...kaller.appspotmail.com
---
lib/maple_tree.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 755ba8b18e14..fe1b01b29201 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -7588,14 +7588,14 @@ static void mt_validate_nulls(struct maple_tree *mt)
* 2. The gap is correctly set in the parents
*/
void mt_validate(struct maple_tree *mt)
+ __must_hold(mas->tree->ma_lock)
{
unsigned char end;
MA_STATE(mas, mt, 0, 0);
- rcu_read_lock();
mas_start(&mas);
if (!mas_is_active(&mas))
- goto done;
+ return;
while (!mte_is_leaf(mas.node))
mas_descend(&mas);
@@ -7616,9 +7616,6 @@ void mt_validate(struct maple_tree *mt)
mas_dfs_postorder(&mas, ULONG_MAX);
}
mt_validate_nulls(mt);
-done:
- rcu_read_unlock();
-
}
EXPORT_SYMBOL_GPL(mt_validate);
--
2.43.0
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