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

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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: syzbot <syzbot+8281086e8a6fbfbd952a@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/e6dd13c5-8db0-4392-6e78-a42ee5d2a1c4@i-love.sakura.ne.jp
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tetsuo Handa 2021-10-02 18:23:02 +09:00 committed by Jens Axboe
parent 41e76c6a3c
commit 06cc978d3f
2 changed files with 2 additions and 1 deletions
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2
block/bdev.c
View File

@ -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;
}

1
block/genhd.c
View File

@ -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);