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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot <syzbot+28a66a9fbc621c939000@syzkaller.appspotmail.com>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.16 0334/1039] block: fix error unwinding in device_add_disk
Date:   Mon, 24 Jan 2022 19:35:23 +0100
Message-Id: <20220124184136.533605897@linuxfoundation.org>
In-Reply-To: <20220124184125.121143506@linuxfoundation.org>
References: <20220124184125.121143506@linuxfoundation.org>
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From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 99d8690aae4b2f0d1d90075de355ac087f820a66 ]

One device_add is called disk->ev will be freed by disk_release, so we
should free it twice.  Fix this by allocating disk->ev after device_add
so that the extra local unwinding can be removed entirely.

Based on an earlier patch from Tetsuo Handa.

Reported-by: syzbot <syzbot+28a66a9fbc621c939000@syzkaller.appspotmail.com>
Tested-by: syzbot <syzbot+28a66a9fbc621c939000@syzkaller.appspotmail.com>
Fixes: 83cbce9574462c6b ("block: add error handling for device_add_disk / add_disk")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211221161851.788424-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/genhd.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 30362aeacac4b..596e43764846b 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -437,10 +437,6 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 		disk->flags |= GENHD_FL_EXT_DEVT;
 	}
 
-	ret = disk_alloc_events(disk);
-	if (ret)
-		goto out_free_ext_minor;
-
 	/* delay uevents, until we scanned partition table */
 	dev_set_uevent_suppress(ddev, 1);
 
@@ -451,7 +447,12 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 		ddev->devt = MKDEV(disk->major, disk->first_minor);
 	ret = device_add(ddev);
 	if (ret)
-		goto out_disk_release_events;
+		goto out_free_ext_minor;
+
+	ret = disk_alloc_events(disk);
+	if (ret)
+		goto out_device_del;
+
 	if (!sysfs_deprecated) {
 		ret = sysfs_create_link(block_depr, &ddev->kobj,
 					kobject_name(&ddev->kobj));
@@ -539,8 +540,6 @@ out_del_block_link:
 		sysfs_remove_link(block_depr, dev_name(ddev));
 out_device_del:
 	device_del(ddev);
-out_disk_release_events:
-	disk_release_events(disk);
 out_free_ext_minor:
 	if (disk->major == BLOCK_EXT_MAJOR)
 		blk_free_ext_minor(disk->first_minor);
-- 
2.34.1