Btrfs: check for read permission on src file in the clone ioctl

The existing code would have allowed you to clone a file that was
only open for writing

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 2b7dd88fc54f..9de6c3a75bfb 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1480,12 +1480,17 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
                 ret = -EBADF;
                 goto out_drop_write;
         }
+
         src = src_file->f_dentry->d_inode;
 
         ret = -EINVAL;
         if (src == inode)
                 goto out_fput;
 
+        /* the src must be open for reading */
+        if (!(src_file->f_mode & FMODE_READ))
+                goto out_fput;
+
         ret = -EISDIR;
         if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode))
                 goto out_fput;