NFSv4: Ensure that we check lock exclusive/shared type against open modes

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@netapp.com>
Cc: stable@vger.kernel.org

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3c787d02131be51b83aab2f52f29c7b540305f4c..ba837d977a1a0aae979409f8db688bee76992b1a 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4726,6 +4726,20 @@ 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))