nfs: explicitly reject LOCK_MAND flock() requests

We have no mechanism to emulate LOCK_MAND locks on NFSv4, so explicitly
return -EINVAL if someone requests it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 1557978ca7b3..b039a17ee941 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -834,6 +834,15 @@ int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
         if (!(fl->fl_flags & FL_FLOCK))
                 return -ENOLCK;
 
+        /*
+         * The NFSv4 protocol doesn't support LOCK_MAND, which is not part of
+         * any standard. In principle we might be able to support LOCK_MAND
+         * on NFSv2/3 since NLMv3/4 support DOS share modes, but for now the
+         * NFS code is not set up for it.
+         */
+        if (fl->fl_type & LOCK_MAND)
+                return -EINVAL;
+
         if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
                 is_local = 1;