linux-kernel - [PATCH AUTOSEL 6.5 08/37] md: don't rely on 'mddev->pers' to be set in mddev

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Date:   Tue,  7 Nov 2023 07:21:19 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yu Kuai <yukuai3@...wei.com>, Song Liu <song@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-raid@...r.kernel.org
Subject: [PATCH AUTOSEL 6.5 08/37] md: don't rely on 'mddev->pers' to be set in mddev_suspend()

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

[ Upstream commit b721e7885eb242aa2459ee66bb42ceef1bcf0f0c ]

'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>
Signed-off-by: Song Liu <song@...nel.org>
Link: https://lore.kernel.org/r/20230825030956.1527023-4-yukuai1@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 78d51dddf3a00..34b7196d9634c 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));
-- 
2.42.0