linux-kernel - [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan

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Message-Id: <20230617103813.3708374-1-yukuai1@huaweicloud.com>
Date:   Sat, 17 Jun 2023 18:38:13 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     hch@....de, axboe@...nel.dk, brauner@...nel.org, hare@...e.de,
        dsterba@...e.com, jinpu.wang@...os.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
        yangerkun@...wei.com
Subject: [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()

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

After commit 2736e8eeb0cc ("block: use the holder as indication for
exclusive opens"), blkdev_get_by_dev() will warn if holder is NULL and
mode contains 'FMODE_EXCL'.

holder from blkdev_get_by_dev() from disk_scan_partitions() is always NULL,
hence it should not use 'FMODE_EXCL', which is broben by the commit. For
consequence, WARN_ON_ONCE() will be triggered from blkdev_get_by_dev()
if user scan partitions with device opened exclusively.

Fix this problem by removing 'FMODE_EXCL' from disk_scan_partitions(),
as it used to be.

Reported-by: syzbot+00cd27751f78817f167b@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=00cd27751f78817f167b
Fixes: 2736e8eeb0cc ("block: use the holder as indication for exclusive opens")
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/genhd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index 2c2f9a716822..1fb964866fd0 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -365,7 +365,8 @@ int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode)
 	}
 
 	set_bit(GD_NEED_PART_SCAN, &disk->state);
-	bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL, NULL);
+	bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
+				 NULL);
 	if (IS_ERR(bdev))
 		ret =  PTR_ERR(bdev);
 	else
-- 
2.39.2