[PATCH 4.9 02/41] fs: completely ignore unknown open flags

[Greg Kroah-Hartman]

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

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

From: Christoph Hellwig <hch@xxxxxx>

commit 629e014bb8349fcf7c1e4df19a842652ece1c945 upstream.

Currently we just stash anything we got into file->f_flags, and the
report it in fcntl(F_GETFD).  This patch just clears out all unknown
flags so that we don't pass them to the fs or report them.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/open.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/open.c
+++ b/fs/open.c
@@ -902,6 +902,12 @@ static inline int build_open_flags(int f
 	int lookup_flags = 0;
 	int acc_mode = ACC_MODE(flags);
 
+	/*
+	 * Clear out all open flags we don't know about so that we don't report
+	 * them in fcntl(F_GETFD) or similar interfaces.
+	 */
+	flags &= VALID_OPEN_FLAGS;
+
 	if (flags & (O_CREAT | __O_TMPFILE))
 		op->mode = (mode & S_IALLUGO) | S_IFREG;
 	else