5 files changed, 77 insertions, 5 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 196a4e5450c0..69f4fc26ee39 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -510,9 +510,9 @@ int ovl_set_nlink_lower(struct dentry *dentry)
 	return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
 }
 
-static unsigned int ovl_get_nlink(struct dentry *lowerdentry,
-				  struct dentry *upperdentry,
-				  unsigned int fallback)
+unsigned int ovl_get_nlink(struct dentry *lowerdentry,
+			   struct dentry *upperdentry,
+			   unsigned int fallback)
 {
 	int nlink_diff;
 	int nlink;
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 2d8b6292fe21..9bc0e580a5b3 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -425,6 +425,11 @@ int ovl_verify_index(struct dentry *index, struct path *lowerstack,
 	if (err)
 		goto fail;
 
+	/* Check if index is orphan and don't warn before cleaning it */
+	if (d_inode(index)->i_nlink == 1 &&
+	    ovl_get_nlink(index, origin.dentry, 0) == 0)
+		err = -ENOENT;
+
 	dput(origin.dentry);
 out:
 	kfree(fh);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index c1321ab38224..60d26605e039 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -263,6 +263,9 @@ int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
 /* inode.c */
 int ovl_set_nlink_upper(struct dentry *dentry);
 int ovl_set_nlink_lower(struct dentry *dentry);
+unsigned int ovl_get_nlink(struct dentry *lowerdentry,
+			   struct dentry *upperdentry,
+			   unsigned int fallback);
 int ovl_setattr(struct dentry *dentry, struct iattr *attr);
 int ovl_getattr(const struct path *path, struct kstat *stat,
 		u32 request_mask, unsigned int flags);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f29ee08cf99f..44dc2d6ffe0f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1069,7 +1069,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			if (err)
 				pr_err("overlayfs: failed to verify index dir origin\n");
 
-			/* Cleanup bad/stale index entries */
+			/* Cleanup bad/stale/orphan index entries */
 			if (!err)
 				err = ovl_indexdir_cleanup(ufs->indexdir,
 							   ufs->upper_mnt,
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 04d5018e728e..c492ba75c659 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -14,6 +14,8 @@
 #include <linux/xattr.h>
 #include <linux/exportfs.h>
 #include <linux/uuid.h>
+#include <linux/namei.h>
+#include <linux/ratelimit.h>
 #include "overlayfs.h"
 #include "ovl_entry.h"
 
@@ -411,6 +413,58 @@ void ovl_inuse_unlock(struct dentry *dentry)
 	}
 }
 
+/* Called must hold OVL_I(inode)->oi_lock */
+static void ovl_cleanup_index(struct dentry *dentry)
+{
+	struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
+	struct dentry *lowerdentry = ovl_dentry_lower(dentry);
+	struct dentry *upperdentry = ovl_dentry_upper(dentry);
+	struct dentry *index = NULL;
+	struct inode *inode;
+	struct qstr name;
+	int err;
+
+	err = ovl_get_index_name(lowerdentry, &name);
+	if (err)
+		goto fail;
+
+	inode = d_inode(upperdentry);
+	if (inode->i_nlink != 1) {
+		pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
+				    upperdentry, inode->i_ino, inode->i_nlink);
+		/*
+		 * We either have a bug with persistent union nlink or a lower
+		 * hardlink was added while overlay is mounted. Adding a lower
+		 * hardlink and then unlinking all overlay hardlinks would drop
+		 * overlay nlink to zero before all upper inodes are unlinked.
+		 * As a safety measure, when that situation is detected, set
+		 * the overlay nlink to the index inode nlink minus one for the
+		 * index entry itself.
+		 */
+		set_nlink(d_inode(dentry), inode->i_nlink - 1);
+		ovl_set_nlink_upper(dentry);
+		goto out;
+	}
+
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+	/* TODO: whiteout instead of cleanup to block future open by handle */
+	index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
+	err = PTR_ERR(index);
+	if (!IS_ERR(index))
+		err = ovl_cleanup(dir, index);
+	inode_unlock(dir);
+	if (err)
+		goto fail;
+
+out:
+	dput(index);
+	return;
+
+fail:
+	pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
+	goto out;
+}
+
 /*
  * Operations that change overlay inode and upper inode nlink need to be
  * synchronized with copy up for persistent nlink accounting.
@@ -473,6 +527,16 @@ out:
 
 void ovl_nlink_end(struct dentry *dentry, bool locked)
 {
-	if (locked)
+	if (locked) {
+		if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
+		    d_inode(dentry)->i_nlink == 0) {
+			const struct cred *old_cred;
+
+			old_cred = ovl_override_creds(dentry->d_sb);
+			ovl_cleanup_index(dentry);
+			revert_creds(old_cred);
+		}
+
 		mutex_unlock(&OVL_I(d_inode(dentry))->lock);
+	}
 }