fs: completely ignore unknown open flags

[ Upstream commit 629e014bb8349fcf7c1e4df19a842652ece1c945 ]

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@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/fs/open.c b/fs/open.c
index ff80b2542989da03313695384bd3bb5f1bf66166..d0169e52d7fefb1c04c0db0605872fd0c062d373 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -881,6 +881,12 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
        int lookup_flags = 0;
        int acc_mode;
 
+       /*
+        * 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