From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 13 Dec 2018 05:57:17 -0600 From: Goldwyn Rodrigues Subject: [PATCH] fs: Evaluate O_WRONLY | O_RDWR to O_RDWR Message-ID: <20181213115717.p7ncktng2ihxw5md@merlin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org To: linux-fsdevel@vger.kernel.org Cc: amir73il@gmail.com, zohar@linux.ibm.com, syzbot+ae82084b07d0297e566b@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, linux-integrity@vger.kernel.org, linux-unionfs@vger.kernel.org, dvyukov@google.com List-ID: A user can open(O_WRONLY | O_RDWR) and the options are valid. However, OPEN_FMODE() evaluates both FMODE_READ and FMODE_WRITE, as negative. We also need to protect the lower layers from this anomaly. Solve it by dropping O_WRONLY, so O_RDWR takes precedence. Signed-off-by: Goldwyn Rodrigues Reported-by: syzbot+ae82084b07d0297e566b@syzkaller.appspotmail.com Fixes: a408e4a86b36 ("ima: open a new file instance if no read permissions") --- fs/open.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/open.c b/fs/open.c index 0285ce7dbd51..3d0a21600fa3 100644 --- a/fs/open.c +++ b/fs/open.c @@ -924,7 +924,12 @@ EXPORT_SYMBOL(open_with_fake_path); static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op) { int lookup_flags = 0; - int acc_mode = ACC_MODE(flags); + int acc_mode; + + if ((flags & (O_RDWR | O_WRONLY)) == (O_RDWR | O_WRONLY)) + flags &= ~O_WRONLY; + + acc_mode = ACC_MODE(flags); /* * Clear out all open flags we don't know about so that we don't report -- 2.16.4