[PATCH] block: delay freeing the gendisk

[PATCH] block: delay freeing the gendisk

[Christoph Hellwig]

blkdev_get_no_open acquires a reference to the block_device through
the block device inode and then tries to acquire a device model
reference to the gendisk.  But at this point the disk migh already
be freed (although the race is free).  Fix this by only freeing the
gendisk from the whole device bdevs ->free_inode callback as well.

Fixes: 22ae8ce8b892 ("block: simplify bdev/disk lookup in blkdev_get")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/genhd.c  | 3 +--
 fs/block_dev.c | 2 ++
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index af4d2ab4a633..e6d782714ad3 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1079,10 +1079,9 @@ static void disk_release(struct device *dev)
 	disk_release_events(disk);
 	kfree(disk->random);
 	xa_destroy(&disk->part_tbl);
-	bdput(disk->part0);
 	if (test_bit(GD_QUEUE_REF, &disk->state) && disk->queue)
 		blk_put_queue(disk->queue);
-	kfree(disk);
+	bdput(disk->part0);
 }
 struct class block_class = {
 	.name		= "block",
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 0c424a0cadaa..1d81f9440404 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -812,6 +812,8 @@ static void bdev_free_inode(struct inode *inode)
 	free_percpu(bdev->bd_stats);
 	kfree(bdev->bd_meta_info);
 
+	if (!bdev_is_partition(bdev))
+		kfree(disk);
 	kmem_cache_free(bdev_cachep, BDEV_I(inode));
 }
 
-- 
2.30.2

Re: [PATCH] block: delay freeing the gendisk

[Christoph Hellwig]

Meh, as-is this doesn't even compile.  I had accidentally commited the
fixup in the following patch.  I'll send the whole series in a bit,
but the this particule patch once fixed is probably still a 5.14
candidate.