linux-kernel - [PATCH 5.15 884/917] bcache: fix use-after-free problem in bcache_device

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Date:   Mon, 15 Nov 2021 18:06:19 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Coly Li <colyli@...e.de>,
        Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.15 884/917] bcache: fix use-after-free problem in bcache_device_free()

From: Coly Li <colyli@...e.de>

commit 8468f45091d2866affed6f6a7aecc20779139173 upstream.

In bcache_device_free(), pointer disk is referenced still in
ida_simple_remove() after blk_cleanup_disk() gets called on this
pointer. This may cause a potential panic by use-after-free on the
disk pointer.

This patch fixes the problem by calling blk_cleanup_disk() after
ida_simple_remove().

Fixes: bc70852fd104 ("bcache: convert to blk_alloc_disk/blk_cleanup_disk")
Signed-off-by: Coly Li <colyli@...e.de>
Cc: Christoph Hellwig <hch@....de>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Ulf Hansson <ulf.hansson@...aro.org>
Cc: stable@...r.kernel.org # v5.14+
Reviewed-by: Christoph Hellwig <hch@....de>
Link: https://lore.kernel.org/r/20211103064917.67383-1-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/md/bcache/super.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -885,9 +885,9 @@ static void bcache_device_free(struct bc
 		bcache_device_detach(d);
 
 	if (disk) {
-		blk_cleanup_disk(disk);
 		ida_simple_remove(&bcache_device_idx,
 				  first_minor_to_idx(disk->first_minor));
+		blk_cleanup_disk(disk);
 	}
 
 	bioset_exit(&d->bio_split);