From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Christoph Hellwig <hch@lst.de>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org
Subject: [PATCH v2] block: genhd: fix double kfree() in __alloc_disk_node()
Date: Mon, 20 Sep 2021 17:31:38 +0900 [thread overview]
Message-ID: <692fdc1a-6396-dcf4-c700-2d822f161053@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20210920080547.GA30362@lst.de>
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>
---
Changes in v2:
Defer bdev->bd_disk assignment instead of resetting to NULL in bdev_alloc().
block/bdev.c | 2 +-
block/genhd.c | 1 +
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/block/bdev.c b/block/bdev.c
index cf2780cb44a7..485a258b0ab3 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -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;
}
diff --git a/block/genhd.c b/block/genhd.c
index 7b6e5e1cf956..496e8458c357 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -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);
--
2.18.4
next prev parent reply other threads:[~2021-09-20 8:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-19 13:35 [syzbot] KASAN: use-after-free Read in bdev_free_inode syzbot
2021-09-19 13:37 ` Tetsuo Handa
2021-09-19 14:44 ` [PATCH] block: genhd: fix double kfree() in __alloc_disk_node() Tetsuo Handa
2021-09-20 6:40 ` Christoph Hellwig
2021-09-20 8:02 ` Tetsuo Handa
2021-09-20 8:05 ` Christoph Hellwig
2021-09-20 8:31 ` Tetsuo Handa [this message]
2021-09-20 8:40 ` [PATCH v2] " Christoph Hellwig
2021-10-09 4:53 ` [syzbot] KASAN: use-after-free Read in bdev_free_inode syzbot
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