Permit hard-linking across bind-mounts as long as the source dir is not

read-only [PL #2624]

diff --git a/fs/namei.c b/fs/namei.c
index 34da5b4..17f4081 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2025,8 +2025,13 @@ asmlinkage long sys_link(const char __user * oldname, const char __user * newnam
        error = path_lookup(to, LOOKUP_PARENT, &nd);
        if (error)
                goto out;
-       error = -EXDEV;
-       if (old_nd.mnt != nd.mnt)
+       /*
+        * We allow hard-links to be created to a bind-mount as long
+        * as the bind-mount is not read-only.  Checking for cross-dev
+        * links is subsumed by the superblock check in vfs_link().
+        */
+       error = -EROFS;
+       if (MNT_IS_RDONLY(old_nd.mnt))
                goto out_release;
        new_dentry = lookup_create(&nd, 0);
        error = PTR_ERR(new_dentry);