Commit 06cc978d authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Jens Axboe
Browse files

block: genhd: fix double kfree() in __alloc_disk_node() 

syzbot is reporting use-after-free read at bdev_free_inode() [1], for
kfree() from __alloc_disk_node() is called before bdev_free_inode()
(which is called after RCU grace period) reads bdev->bd_disk and calls
kfree(bdev->bd_disk).

Fix use-after-free read followed by double kfree() problem
by making sure that bdev->bd_disk is NULL when calling iput().

Link: https://syzkaller.appspot.com/bug?extid=8281086e8a6fbfbd952a

 [1]
Reported-by: default avatarsyzbot <syzbot+8281086e8a6fbfbd952a@syzkaller.appspotmail.com>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/e6dd13c5-8db0-4392-6e78-a42ee5d2a1c4@i-love.sakura.ne.jp


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 41e76c6a

block/bdev.c

+1 −1
Original line number Diff line number Diff line
@@ -490,7 +490,6 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno) 
	bdev = I_BDEV(inode);

	mutex_init(&bdev->bd_fsfreeze_mutex);

	spin_lock_init(&bdev->bd_size_lock);

	bdev->bd_disk = disk;

	bdev->bd_partno = partno;

	bdev->bd_inode = inode;

	bdev->bd_stats = alloc_percpu(struct disk_stats);
@@ -498,6 +497,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno) 
		iput(inode);

		return NULL;

	}

	bdev->bd_disk = disk;

	return bdev;

}

block/genhd.c

+1 −0
Original line number Diff line number Diff line
@@ -1268,6 +1268,7 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id, 


out_destroy_part_tbl:

	xa_destroy(&disk->part_tbl);

	disk->part0->bd_disk = NULL;

	iput(disk->part0->bd_inode);

out_free_bdi:

	bdi_put(disk->bdi);