linux-kernel - Re: Kernel null pointer dereference on stopping raid device

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Date:   Wed, 14 Jun 2023 00:22:38 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Ayush Jain <ayush.jain3@....com>
Cc:     sfr@...b.auug.org.au,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Wyes Karny <wyes.karny@....com>, hch@...radead.org,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org
Subject: Re: Kernel null pointer dereference on stopping raid device

Hi Ayush,

can you try this patch?

diff --git a/drivers/md/md.c b/drivers/md/md.c
index ca0de7ddd9434d..828c4e6b9c5013 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2460,7 +2460,7 @@ static void export_rdev(struct md_rdev *rdev, struct mddev *mddev)
 	if (test_bit(AutoDetected, &rdev->flags))
 		md_autodetect_dev(rdev->bdev->bd_dev);
 #endif
-	blkdev_put(rdev->bdev, mddev->major_version == -2 ? &claim_rdev : rdev);
+	blkdev_put(rdev->bdev, &claim_rdev);
 	rdev->bdev = NULL;
 	kobject_put(&rdev->kobj);
 }
@@ -3644,7 +3644,7 @@ static struct md_rdev *md_import_device(dev_t newdev, int super_format, int supe
 		goto out_clear_rdev;
 
 	rdev->bdev = blkdev_get_by_dev(newdev, BLK_OPEN_READ | BLK_OPEN_WRITE,
-			super_format == -2 ? &claim_rdev : rdev, NULL);
+			&claim_rdev, NULL);
 	if (IS_ERR(rdev->bdev)) {
 		pr_warn("md: could not open device unknown-block(%u,%u).\n",
 			MAJOR(newdev), MINOR(newdev));
@@ -3681,7 +3681,7 @@ static struct md_rdev *md_import_device(dev_t newdev, int super_format, int supe
 	return rdev;
 
 out_blkdev_put:
-	blkdev_put(rdev->bdev, super_format == -2 ? &claim_rdev : rdev);
+	blkdev_put(rdev->bdev, &claim_rdev);
 out_clear_rdev:
 	md_rdev_clear(rdev);
 out_free_rdev: