[PATCH 7.2 242/242] smb: client: drain outstanding I/O before truncating on O_TRUNC open

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

7.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paulo Alcantara <pc@manguebit.org>

commit 3581f843defa0bb30fd7da1e7dba170465e13a95 upstream.

cifs_do_truncate() flushes the pagecache with filemap_write_and_wait()
before resetting the file size to zero, but that does not wait for
direct/async I/O that was already in flight, which can complete after the
truncate and reinstate stale data past the new EOF.

Drain outstanding netfs I/O with netfs_wait_for_outstanding_io()
before resizing the file.

Reported-by: Frank Sorenson <sorenson@redhat.com>
Fixes: a8603b52b39f ("smb: client: fix data corruption with concurrent writes and O_TRUNC")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/smb/client/file.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -1012,6 +1012,8 @@ static int cifs_do_truncate(const unsign
 	}
 	mapping_set_error(inode->i_mapping, rc);
 
+	netfs_wait_for_outstanding_io(inode);
+
 	cfile = find_writable_file(cinode, FIND_FSUID_ONLY);
 	rc = cifs_file_flush(xid, inode, cfile);
 	if (!rc) {