[PATCH 4/4] NFSv4: Ensure that we check lock exclusive/shared type against open modes

[Luis Henriques]

From: Trond Myklebust <Trond.Myklebust at netapp.com>

BugLink: http://bugs.launchpad.net/bugs/974664

Since we may be simulating flock() locks using NFS byte range locks,
we can't rely on the VFS having checked the file open mode for us.

Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Cc: stable at vger.kernel.org
(cherry picked from commit 5de4815015e550bdd33f39650554325540356f0c git://git.linux-nfs.org/projects/trondmy/linux-nfs.git)

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/nfs/nfs4proc.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 39c9cd2..8b16560 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4601,6 +4601,20 @@ nfs4_proc_lock(struct file *filp, int cmd, struct file_lock *request)
 
 	if (state == NULL)
 		return -ENOLCK;
+	/*
+	 * Don't rely on the VFS having checked the file open mode,
+	 * since it won't do this for flock() locks.
+	 */
+	switch (request->fl_type & (F_RDLCK|F_WRLCK|F_UNLCK)) {
+	case F_RDLCK:
+		if (!(filp->f_mode & FMODE_READ))
+			return -EBADF;
+		break;
+	case F_WRLCK:
+		if (!(filp->f_mode & FMODE_WRITE))
+			return -EBADF;
+	}
+
 	do {
 		status = nfs4_proc_setlk(state, cmd, request);
 		if ((status != -EAGAIN) || IS_SETLK(cmd))
-- 
1.7.9.5