[PATCH 5.4 22/92] fuse: fix leak of fuse_io_priv

[Greg Kroah-Hartman]

From: Miklos Szeredi <mszeredi@xxxxxxxxxx>

commit f1ebdeffc6f325e30e0ddb9f7a70f1370fa4b851 upstream.

exit_aio() is sometimes stuck in wait_for_completion() after aio is issued
with direct IO and the task receives a signal.

The reason is failure to call ->ki_complete() due to a leaked reference to
fuse_io_priv.  This happens in fuse_async_req_send() if
fuse_simple_background() returns an error (e.g. -EINTR).

In this case the error value is propagated via io->err, so return success
to not confuse callers.

This issue is tracked as a virtio-fs issue:
https://gitlab.com/virtio-fs/qemu/issues/14

Reported-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
Fixes: 45ac96ed7c36 ("fuse: convert direct_io to simple api")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.4
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/fuse/file.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -713,8 +713,10 @@ static ssize_t fuse_async_req_send(struc
 
 	ia->ap.args.end = fuse_aio_complete_req;
 	err = fuse_simple_background(fc, &ia->ap.args, GFP_KERNEL);
+	if (err)
+		fuse_aio_complete_req(fc, &ia->ap.args, err);
 
-	return err ?: num_bytes;
+	return num_bytes;
 }
 
 static ssize_t fuse_send_read(struct fuse_io_args *ia, loff_t pos, size_t count,