[PATCH -V26 04/16] fs: Don't allow to create hardlink for deleted file

[Aneesh Kumar K.V]

Add inode->i_nlink == 0 check in VFS. Some of the file systems
do this internally. A followup patch will remove those instance.
This is needed to ensure that with link by handle we don't allow
to create hardlink of an unlinked file. The check also prevent a race
between unlink and link

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
---
 fs/namei.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 6b0536f..a8346fa 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3318,7 +3318,11 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
 		return error;
 
 	mutex_lock(&inode->i_mutex);
-	error = dir->i_op->link(old_dentry, dir, new_dentry);
+	/* Make sure we don't allow creating hardlink to an unlinked file */
+	if (inode->i_nlink == 0)
+		error =  -ENOENT;
+	else
+		error = dir->i_op->link(old_dentry, dir, new_dentry);
 	mutex_unlock(&inode->i_mutex);
 	if (!error)
 		fsnotify_link(dir, inode, new_dentry);
-- 
1.7.1

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