linux-kernel - [PATCH] md: use RCU lock to protect traversal in md_spares_need

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Date: Thu,  4 Jan 2024 21:36:29 +0800
From: Li Lingfeng <lilingfeng@...weicloud.com>
To: song@...nel.org
Cc: linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	linan122@...wei.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	lilingfeng@...weicloud.com,
	lilingfeng3@...wei.com
Subject: [PATCH] md: use RCU lock to protect traversal in md_spares_need_change()

From: Li Lingfeng <lilingfeng3@...wei.com>

Since md_start_sync() will be called without the protect of mddev_lock,
and it can run concurrently with array reconfiguration, traversal of rdev
in it should be protected by RCU lock.
Commit bc08041b32ab ("md: suspend array in md_start_sync() if array need
reconfiguration") added md_spares_need_change() to md_start_sync(),
casusing use of rdev without any protection.
Fix this by adding RCU lock in md_spares_need_change().

Fixes: bc08041b32ab ("md: suspend array in md_start_sync() if array need reconfiguration")
Signed-off-by: Li Lingfeng <lilingfeng3@...wei.com>
---
 drivers/md/md.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9bdd57324c37..902b43b65052 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9228,9 +9228,14 @@ static bool md_spares_need_change(struct mddev *mddev)
 {
 	struct md_rdev *rdev;
 
-	rdev_for_each(rdev, mddev)
-		if (rdev_removeable(rdev) || rdev_addable(rdev))
+	rcu_read_lock();
+	rdev_for_each_rcu(rdev, mddev) {
+		if (rdev_removeable(rdev) || rdev_addable(rdev)) {
+			rcu_read_unlock();
 			return true;
+		}
+	}
+	rcu_read_unlock();
 	return false;
 }
 
-- 
2.31.1