From 8aa5c23ef81ba86d8ddf2791cbe8db17f3d6bada Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Tue, 12 Nov 2019 11:49:04 +0100
Subject: [PATCH] fuse: verify write return

commit 8aab336b14c115c6bf1d4baeb9247e41ed9ce6de upstream.

Make sure filesystem is not returning a bogus number of bytes written.

Fixes: ea9b9907b82a ("fuse: implement perform_write")
Cc: <stable@vger.kernel.org> # v2.6.26
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/fuse/file.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a28f84b17f4da..a63d779eac104 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1098,6 +1098,8 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,
 	ia->write.in.flags = fuse_write_flags(iocb);
 
 	err = fuse_simple_request(fc, &ap->args);
+	if (!err && ia->write.out.size > count)
+		err = -EIO;
 
 	offset = ap->descs[0].offset;
 	count = ia->write.out.size;
-- 
2.50.1