linux-kernel - [PATCH -next v2 3/7] md: don't rely on 'mddev->pers' to be set in mddev

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Message-Id: <20230825030956.1527023-4-yukuai1@huaweicloud.com>
Date:   Fri, 25 Aug 2023 11:09:52 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     agk@...hat.com, snitzer@...nel.org, dm-devel@...hat.com,
        song@...nel.org, xni@...hat.com
Cc:     linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
        yangerkun@...wei.com
Subject: [PATCH -next v2 3/7] md: don't rely on 'mddev->pers' to be set in mddev_suspend()

From: Yu Kuai <yukuai3@...wei.com>

'active_io' used to be initialized while the array is running, and
'mddev->pers' is set while the array is running as well. Hence caller
must hold 'reconfig_mutex' and guarantee 'mddev->pers' is set before
calling mddev_suspend().

Now that 'active_io' is initialized when mddev is allocated, such
restriction doesn't exist anymore. In the meantime, follow up patches
will refactor mddev_suspend(), hence add checking for 'mddev->pers' to
prevent null-ptr-deref.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/md/md.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index e6faeb73172d..e787900d51d7 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -449,7 +449,7 @@ void mddev_suspend(struct mddev *mddev)
 	set_bit(MD_ALLOW_SB_UPDATE, &mddev->flags);
 	percpu_ref_kill(&mddev->active_io);
 
-	if (mddev->pers->prepare_suspend)
+	if (mddev->pers && mddev->pers->prepare_suspend)
 		mddev->pers->prepare_suspend(mddev);
 
 	wait_event(mddev->sb_wait, percpu_ref_is_zero(&mddev->active_io));
-- 
2.39.2