[PATCH] block/fops: fix refcount underflow in __blkdev_direct_IO()

[Wentao Liang <vulab@iscas.ac.cn>]

__blkdev_direct_IO() calls bio_get() and bio_put() around
I/O operations, but if the I/O fails, the error path may call
bio_put() twice, causing a refcount underflow.

Fix this by moving the bio_put() call from the error path into
the cleanup section that is only executed once, regardless of
whether the I/O succeeded or failed.

Fixes: 3d8b5a22d404 ("block: add support to pass user meta buffer")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
 block/fops.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/fops.c b/block/fops.c
index bb6642b45937..4dd1e40c7d4e 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -286,6 +286,8 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 	bio_release_pages(bio, false);
 	bio_clear_flag(bio, BIO_REFFED);
 	bio_put(bio);
+	if (bio == &dio->bio)
+		bio_put(bio);
 	blk_finish_plug(&plug);
 	return ret;
 }
-- 
2.34.1