FAILED: patch "[PATCH] bcache: fix use-after-free problem in bcache_device_free()" failed to apply to 5.14-stable tree

From: <gregkh@linuxfoundation.org>
Date: 2021-11-15 14:39:11
Subsystem: bcache (block layer cache), the rest · Maintainers: Coly Li, Kent Overstreet, Linus Torvalds

The patch below does not apply to the 5.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to [off-list ref].

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8468f45091d2866affed6f6a7aecc20779139173 Mon Sep 17 00:00:00 2001
From: Coly Li <redacted>
Date: Wed, 3 Nov 2021 14:49:17 +0800
Subject: [PATCH] bcache: fix use-after-free problem in bcache_device_free()

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 <redacted>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ulf Hansson <redacted>
Cc: stable@vger.kernel.org # v5.14+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211103064917.67383-1-colyli@suse.de (local)
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 84a48eed8e24..a7bb3355b776 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -885,9 +885,9 @@ static void bcache_device_free(struct bcache_device *d)
 		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);
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