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

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Message-Id: <20170710171051.962864950@linuxfoundation.org>
Date:   Mon, 10 Jul 2017 19:10:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 4.9 02/41] fs: completely ignore unknown open flags

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

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

From: Christoph Hellwig <hch@....de>

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@....de>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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