Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "This work from Amir adds NFS export capability to overlayfs. NFS
  exporting an overlay filesystem is a challange because we want to keep
  track of any copy-up of a file or directory between encoding the file
  handle and decoding it.

  This is achieved by indexing copied up objects by lower layer file
  handle. The index is already used for hard links, this patchset
  extends the use to NFS file handle decoding"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (51 commits)
  ovl: check ERR_PTR() return value from ovl_encode_fh()
  ovl: fix regression in fsnotify of overlay merge dir
  ovl: wire up NFS export operations
  ovl: lookup indexed ancestor of lower dir
  ovl: lookup connected ancestor of dir in inode cache
  ovl: hash non-indexed dir by upper inode for NFS export
  ovl: decode pure lower dir file handles
  ovl: decode indexed dir file handles
  ovl: decode lower file handles of unlinked but open files
  ovl: decode indexed non-dir file handles
  ovl: decode lower non-dir file handles
  ovl: encode lower file handles
  ovl: copy up before encoding non-connectable dir file handle
  ovl: encode non-indexed upper file handles
  ovl: decode connected upper dir file handles
  ovl: decode pure upper file handles
  ovl: encode pure upper file handles
  ovl: document NFS export
  vfs: factor out helpers d_instantiate_anon() and d_alloc_anon()
  ovl: store 'has_upper' and 'opaque' as bit flags
  ...

1 files changed, 389 insertions, 144 deletions

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index beb945e1963c..de3e6da1d5a5 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -9,6 +9,7 @@
 
 #include <linux/fs.h>
 #include <linux/cred.h>
+#include <linux/ctype.h>
 #include <linux/namei.h>
 #include <linux/xattr.h>
 #include <linux/ratelimit.h>
@@ -84,15 +85,54 @@ invalid:
 
 static int ovl_acceptable(void *ctx, struct dentry *dentry)
 {
-	return 1;
+	/*
+	 * A non-dir origin may be disconnected, which is fine, because
+	 * we only need it for its unique inode number.
+	 */
+	if (!d_is_dir(dentry))
+		return 1;
+
+	/* Don't decode a deleted empty directory */
+	if (d_unhashed(dentry))
+		return 0;
+
+	/* Check if directory belongs to the layer we are decoding from */
+	return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root);
 }
 
-static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
+/*
+ * Check validity of an overlay file handle buffer.
+ *
+ * Return 0 for a valid file handle.
+ * Return -ENODATA for "origin unknown".
+ * Return <0 for an invalid file handle.
+ */
+int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
 {
-	int res;
+	if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len)
+		return -EINVAL;
+
+	if (fh->magic != OVL_FH_MAGIC)
+		return -EINVAL;
+
+	/* Treat larger version and unknown flags as "origin unknown" */
+	if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
+		return -ENODATA;
+
+	/* Treat endianness mismatch as "origin unknown" */
+	if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
+	    (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
+		return -ENODATA;
+
+	return 0;
+}
+
+static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
+{
+	int res, err;
 	struct ovl_fh *fh = NULL;
 
-	res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
+	res = vfs_getxattr(dentry, name, NULL, 0);
 	if (res < 0) {
 		if (res == -ENODATA || res == -EOPNOTSUPP)
 			return NULL;
@@ -102,28 +142,20 @@ static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
 	if (res == 0)
 		return NULL;
 
-	fh  = kzalloc(res, GFP_KERNEL);
+	fh = kzalloc(res, GFP_KERNEL);
 	if (!fh)
 		return ERR_PTR(-ENOMEM);
 
-	res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, fh, res);
+	res = vfs_getxattr(dentry, name, fh, res);
 	if (res < 0)
 		goto fail;
 
-	if (res < sizeof(struct ovl_fh) || res < fh->len)
-		goto invalid;
-
-	if (fh->magic != OVL_FH_MAGIC)
+	err = ovl_check_fh_len(fh, res);
+	if (err < 0) {
+		if (err == -ENODATA)
+			goto out;
 		goto invalid;
-
-	/* Treat larger version and unknown flags as "origin unknown" */
-	if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
-		goto out;
-
-	/* Treat endianness mismatch as "origin unknown" */
-	if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
-	    (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
-		goto out;
+	}
 
 	return fh;
 
@@ -139,47 +171,41 @@ invalid:
 	goto out;
 }
 
-static struct dentry *ovl_get_origin(struct dentry *dentry,
-				     struct vfsmount *mnt)
+struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
 {
-	struct dentry *origin = NULL;
-	struct ovl_fh *fh = ovl_get_origin_fh(dentry);
+	struct dentry *real;
 	int bytes;
 
-	if (IS_ERR_OR_NULL(fh))
-		return (struct dentry *)fh;
-
 	/*
 	 * Make sure that the stored uuid matches the uuid of the lower
 	 * layer where file handle will be decoded.
 	 */
 	if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
-		goto out;
+		return NULL;
 
 	bytes = (fh->len - offsetof(struct ovl_fh, fid));
-	origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
-				    bytes >> 2, (int)fh->type,
-				    ovl_acceptable, NULL);
-	if (IS_ERR(origin)) {
-		/* Treat stale file handle as "origin unknown" */
-		if (origin == ERR_PTR(-ESTALE))
-			origin = NULL;
-		goto out;
+	real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
+				  bytes >> 2, (int)fh->type,
+				  ovl_acceptable, mnt);
+	if (IS_ERR(real)) {
+		/*
+		 * Treat stale file handle to lower file as "origin unknown".
+		 * upper file handle could become stale when upper file is
+		 * unlinked and this information is needed to handle stale
+		 * index entries correctly.
+		 */
+		if (real == ERR_PTR(-ESTALE) &&
+		    !(fh->flags & OVL_FH_FLAG_PATH_UPPER))
+			real = NULL;
+		return real;
 	}
 
-	if (ovl_dentry_weird(origin) ||
-	    ((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT))
-		goto invalid;
-
-out:
-	kfree(fh);
-	return origin;
+	if (ovl_dentry_weird(real)) {
+		dput(real);
+		return NULL;
+	}
 
-invalid:
-	pr_warn_ratelimited("overlayfs: invalid origin (%pd2)\n", origin);
-	dput(origin);
-	origin = NULL;
-	goto out;
+	return real;
 }
 
 static bool ovl_is_opaquedir(struct dentry *dentry)
@@ -284,47 +310,81 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 }
 
 
-static int ovl_check_origin(struct dentry *upperdentry,
-			    struct ovl_path *lower, unsigned int numlower,
-			    struct ovl_path **stackp, unsigned int *ctrp)
+int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
+			struct dentry *upperdentry, struct ovl_path **stackp)
 {
-	struct vfsmount *mnt;
 	struct dentry *origin = NULL;
 	int i;
 
-	for (i = 0; i < numlower; i++) {
-		mnt = lower[i].layer->mnt;
-		origin = ovl_get_origin(upperdentry, mnt);
-		if (IS_ERR(origin))
-			return PTR_ERR(origin);
-
+	for (i = 0; i < ofs->numlower; i++) {
+		origin = ovl_decode_fh(fh, ofs->lower_layers[i].mnt);
 		if (origin)
 			break;
 	}
 
 	if (!origin)
-		return 0;
+		return -ESTALE;
+	else if (IS_ERR(origin))
+		return PTR_ERR(origin);
+
+	if (upperdentry && !ovl_is_whiteout(upperdentry) &&
+	    ((d_inode(origin)->i_mode ^ d_inode(upperdentry)->i_mode) & S_IFMT))
+		goto invalid;
 
-	BUG_ON(*ctrp);
 	if (!*stackp)
 		*stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL);
 	if (!*stackp) {
 		dput(origin);
 		return -ENOMEM;
 	}
-	**stackp = (struct ovl_path){.dentry = origin, .layer = lower[i].layer};
-	*ctrp = 1;
+	**stackp = (struct ovl_path){
+		.dentry = origin,
+		.layer = &ofs->lower_layers[i]
+	};
+
+	return 0;
+
+invalid:
+	pr_warn_ratelimited("overlayfs: invalid origin (%pd2, ftype=%x, origin ftype=%x).\n",
+			    upperdentry, d_inode(upperdentry)->i_mode & S_IFMT,
+			    d_inode(origin)->i_mode & S_IFMT);
+	dput(origin);
+	return -EIO;
+}
+
+static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
+			    struct ovl_path **stackp, unsigned int *ctrp)
+{
+	struct ovl_fh *fh = ovl_get_fh(upperdentry, OVL_XATTR_ORIGIN);
+	int err;
+
+	if (IS_ERR_OR_NULL(fh))
+		return PTR_ERR(fh);
+
+	err = ovl_check_origin_fh(ofs, fh, upperdentry, stackp);
+	kfree(fh);
+
+	if (err) {
+		if (err == -ESTALE)
+			return 0;
+		return err;
+	}
+
+	if (WARN_ON(*ctrp))
+		return -EIO;
 
+	*ctrp = 1;
 	return 0;
 }
 
 /*
- * Verify that @fh matches the origin file handle stored in OVL_XATTR_ORIGIN.
+ * Verify that @fh matches the file handle stored in xattr @name.
  * Return 0 on match, -ESTALE on mismatch, < 0 on error.
  */
-static int ovl_verify_origin_fh(struct dentry *dentry, const struct ovl_fh *fh)
+static int ovl_verify_fh(struct dentry *dentry, const char *name,
+			 const struct ovl_fh *fh)
 {
-	struct ovl_fh *ofh = ovl_get_origin_fh(dentry);
+	struct ovl_fh *ofh = ovl_get_fh(dentry, name);
 	int err = 0;
 
 	if (!ofh)
@@ -341,28 +401,28 @@ static int ovl_verify_origin_fh(struct dentry *dentry, const struct ovl_fh *fh)
 }
 
 /*
- * Verify that an inode matches the origin file handle stored in upper inode.
+ * Verify that @real dentry matches the file handle stored in xattr @name.
  *
- * If @set is true and there is no stored file handle, encode and store origin
- * file handle in OVL_XATTR_ORIGIN.
+ * If @set is true and there is no stored file handle, encode @real and store
+ * file handle in xattr @name.
  *
- * Return 0 on match, -ESTALE on mismatch, < 0 on error.
+ * Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
  */
-int ovl_verify_origin(struct dentry *dentry, struct dentry *origin,
-		      bool is_upper, bool set)
+int ovl_verify_set_fh(struct dentry *dentry, const char *name,
+		      struct dentry *real, bool is_upper, bool set)
 {
 	struct inode *inode;
 	struct ovl_fh *fh;
 	int err;
 
-	fh = ovl_encode_fh(origin, is_upper);
+	fh = ovl_encode_fh(real, is_upper);
 	err = PTR_ERR(fh);
 	if (IS_ERR(fh))
 		goto fail;
 
-	err = ovl_verify_origin_fh(dentry, fh);
+	err = ovl_verify_fh(dentry, name, fh);
 	if (set && err == -ENODATA)
-		err = ovl_do_setxattr(dentry, OVL_XATTR_ORIGIN, fh, fh->len, 0);
+		err = ovl_do_setxattr(dentry, name, fh, fh->len, 0);
 	if (err)
 		goto fail;
 
@@ -371,45 +431,71 @@ out:
 	return err;
 
 fail:
-	inode = d_inode(origin);
-	pr_warn_ratelimited("overlayfs: failed to verify origin (%pd2, ino=%lu, err=%i)\n",
-			    origin, inode ? inode->i_ino : 0, err);
+	inode = d_inode(real);
+	pr_warn_ratelimited("overlayfs: failed to verify %s (%pd2, ino=%lu, err=%i)\n",
+			    is_upper ? "upper" : "origin", real,
+			    inode ? inode->i_ino : 0, err);
 	goto out;
 }
 
+/* Get upper dentry from index */
+struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
+{
+	struct ovl_fh *fh;
+	struct dentry *upper;
+
+	if (!d_is_dir(index))
+		return dget(index);
+
+	fh = ovl_get_fh(index, OVL_XATTR_UPPER);
+	if (IS_ERR_OR_NULL(fh))
+		return ERR_CAST(fh);
+
+	upper = ovl_decode_fh(fh, ofs->upper_mnt);
+	kfree(fh);
+
+	if (IS_ERR_OR_NULL(upper))
+		return upper ?: ERR_PTR(-ESTALE);
+
+	if (!d_is_dir(upper)) {
+		pr_warn_ratelimited("overlayfs: invalid index upper (%pd2, upper=%pd2).\n",
+				    index, upper);
+		dput(upper);
+		return ERR_PTR(-EIO);
+	}
+
+	return upper;
+}
+
+/* Is this a leftover from create/whiteout of directory index entry? */
+static bool ovl_is_temp_index(struct dentry *index)
+{
+	return index->d_name.name[0] == '#';
+}
+
 /*
  * Verify that an index entry name matches the origin file handle stored in
  * OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
  * Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
  */
-int ovl_verify_index(struct dentry *index, struct ovl_path *lower,
-		     unsigned int numlower)
+int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
 {
 	struct ovl_fh *fh = NULL;
 	size_t len;
 	struct ovl_path origin = { };
 	struct ovl_path *stack = &origin;
-	unsigned int ctr = 0;
+	struct dentry *upper = NULL;
 	int err;
 
 	if (!d_inode(index))
 		return 0;
 
-	/*
-	 * Directory index entries are going to be used for looking up
-	 * redirected upper dirs by lower dir fh when decoding an overlay
-	 * file handle of a merge dir. Whiteout index entries are going to be
-	 * used as an indication that an exported overlay file handle should
-	 * be treated as stale (i.e. after unlink of the overlay inode).
-	 * We don't know the verification rules for directory and whiteout
-	 * index entries, because they have not been implemented yet, so return
-	 * EINVAL if those entries are found to abort the mount to avoid
-	 * corrupting an index that was created by a newer kernel.
-	 */
-	err = -EINVAL;
-	if (d_is_dir(index) || ovl_is_whiteout(index))
+	/* Cleanup leftover from index create/cleanup attempt */
+	err = -ESTALE;
+	if (ovl_is_temp_index(index))
 		goto fail;
 
+	err = -EINVAL;
 	if (index->d_name.len < sizeof(struct ovl_fh)*2)
 		goto fail;
 
@@ -420,26 +506,68 @@ int ovl_verify_index(struct dentry *index, struct ovl_path *lower,
 		goto fail;
 
 	err = -EINVAL;
-	if (hex2bin((u8 *)fh, index->d_name.name, len) || len != fh->len)
+	if (hex2bin((u8 *)fh, index->d_name.name, len))
 		goto fail;
 
-	err = ovl_verify_origin_fh(index, fh);
+	err = ovl_check_fh_len(fh, len);
 	if (err)
 		goto fail;
 
-	err = ovl_check_origin(index, lower, numlower, &stack, &ctr);
-	if (!err && !ctr)
-		err = -ESTALE;
+	/*
+	 * Whiteout index entries are used as an indication that an exported
+	 * overlay file handle should be treated as stale (i.e. after unlink
+	 * of the overlay inode). These entries contain no origin xattr.
+	 */
+	if (ovl_is_whiteout(index))
+		goto out;
+
+	/*
+	 * Verifying directory index entries are not stale is expensive, so
+	 * only verify stale dir index if NFS export is enabled.
+	 */
+	if (d_is_dir(index) && !ofs->config.nfs_export)
+		goto out;
+
+	/*
+	 * Directory index entries should have 'upper' xattr pointing to the
+	 * real upper dir. Non-dir index entries are hardlinks to the upper
+	 * real inode. For non-dir index, we can read the copy up origin xattr
+	 * directly from the index dentry, but for dir index we first need to
+	 * decode the upper directory.
+	 */
+	upper = ovl_index_upper(ofs, index);
+	if (IS_ERR_OR_NULL(upper)) {
+		err = PTR_ERR(upper);
+		/*
+		 * Directory index entries with no 'upper' xattr need to be
+		 * removed. When dir index entry has a stale 'upper' xattr,
+		 * we assume that upper dir was removed and we treat the dir
+		 * index as orphan entry that needs to be whited out.
+		 */
+		if (err == -ESTALE)
+			goto orphan;
+		else if (!err)
+			err = -ESTALE;
+		goto fail;
+	}
+
+	err = ovl_verify_fh(upper, OVL_XATTR_ORIGIN, fh);
+	dput(upper);
 	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(origin.dentry, index, 0) == 0)
-		err = -ENOENT;
+	/* Check if non-dir index is orphan and don't warn before cleaning it */
+	if (!d_is_dir(index) && d_inode(index)->i_nlink == 1) {
+		err = ovl_check_origin_fh(ofs, fh, index, &stack);
+		if (err)
+			goto fail;
+
+		if (ovl_get_nlink(origin.dentry, index, 0) == 0)
+			goto orphan;
+	}
 
-	dput(origin.dentry);
 out:
+	dput(origin.dentry);
 	kfree(fh);
 	return err;
 
@@ -447,6 +575,28 @@ fail:
 	pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, ftype=%x, err=%i)\n",
 			    index, d_inode(index)->i_mode & S_IFMT, err);
 	goto out;
+
+orphan:
+	pr_warn_ratelimited("overlayfs: orphan index entry (%pd2, ftype=%x, nlink=%u)\n",
+			    index, d_inode(index)->i_mode & S_IFMT,
+			    d_inode(index)->i_nlink);
+	err = -ENOENT;
+	goto out;
+}
+
+static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name)
+{
+	char *n, *s;
+
+	n = kzalloc(fh->len * 2, GFP_KERNEL);
+	if (!n)
+		return -ENOMEM;
+
+	s  = bin2hex(n, fh, fh->len);
+	*name = (struct qstr) QSTR_INIT(n, s - n);
+
+	return 0;
+
 }
 
 /*
@@ -466,35 +616,58 @@ fail:
  */
 int ovl_get_index_name(struct dentry *origin, struct qstr *name)
 {
-	int err;
 	struct ovl_fh *fh;
-	char *n, *s;
+	int err;
 
 	fh = ovl_encode_fh(origin, false);
 	if (IS_ERR(fh))
 		return PTR_ERR(fh);
 
-	err = -ENOMEM;
-	n = kzalloc(fh->len * 2, GFP_KERNEL);
-	if (n) {
-		s  = bin2hex(n, fh, fh->len);
-		*name = (struct qstr) QSTR_INIT(n, s - n);
-		err = 0;
-	}
-	kfree(fh);
+	err = ovl_get_index_name_fh(fh, name);
 
+	kfree(fh);
 	return err;
+}
+
+/* Lookup index by file handle for NFS export */
+struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
+{
+	struct dentry *index;
+	struct qstr name;
+	int err;
+
+	err = ovl_get_index_name_fh(fh, &name);
+	if (err)
+		return ERR_PTR(err);
+
+	index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
+	kfree(name.name);
+	if (IS_ERR(index)) {
+		if (PTR_ERR(index) == -ENOENT)
+			index = NULL;
+		return index;
+	}
 
+	if (d_is_negative(index))
+		err = 0;
+	else if (ovl_is_whiteout(index))
+		err = -ESTALE;
+	else if (ovl_dentry_weird(index))
+		err = -EIO;
+	else
+		return index;
+
+	dput(index);
+	return ERR_PTR(err);
 }
 
-static struct dentry *ovl_lookup_index(struct dentry *dentry,
-				       struct dentry *upper,
-				       struct dentry *origin)
+struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
+				struct dentry *origin, bool verify)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 	struct dentry *index;
 	struct inode *inode;
 	struct qstr name;
+	bool is_dir = d_is_dir(origin);
 	int err;
 
 	err = ovl_get_index_name(origin, &name);
@@ -518,8 +691,16 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
 	inode = d_inode(index);
 	if (d_is_negative(index)) {
 		goto out_dput;
-	} else if (upper && d_inode(upper) != inode) {
-		goto out_dput;
+	} else if (ovl_is_whiteout(index) && !verify) {
+		/*
+		 * When index lookup is called with !verify for decoding an
+		 * overlay file handle, a whiteout index implies that decode
+		 * should treat file handle as stale and no need to print a
+		 * warning about it.
+		 */
+		dput(index);
+		index = ERR_PTR(-ESTALE);
+		goto out;
 	} else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
 		   ((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
 		/*
@@ -533,8 +714,25 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
 				    index, d_inode(index)->i_mode & S_IFMT,
 				    d_inode(origin)->i_mode & S_IFMT);
 		goto fail;
-	}
+	} else if (is_dir && verify) {
+		if (!upper) {
+			pr_warn_ratelimited("overlayfs: suspected uncovered redirected dir found (origin=%pd2, index=%pd2).\n",
+					    origin, index);
+			goto fail;
+		}
 
+		/* Verify that dir index 'upper' xattr points to upper dir */
+		err = ovl_verify_upper(index, upper, false);
+		if (err) {
+			if (err == -ESTALE) {
+				pr_warn_ratelimited("overlayfs: suspected multiply redirected dir found (upper=%pd2, origin=%pd2, index=%pd2).\n",
+						    upper, origin, index);
+			}
+			goto fail;
+		}
+	} else if (upper && d_inode(upper) != inode) {
+		goto out_dput;
+	}
 out:
 	kfree(name.name);
 	return index;
@@ -572,16 +770,25 @@ int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
 	return (idx < oe->numlower) ? idx + 1 : -1;
 }
 
-static int ovl_find_layer(struct ovl_fs *ofs, struct ovl_path *path)
+/* Fix missing 'origin' xattr */
+static int ovl_fix_origin(struct dentry *dentry, struct dentry *lower,
+			  struct dentry *upper)
 {
-	int i;
+	int err;
 
-	for (i = 0; i < ofs->numlower; i++) {
-		if (ofs->lower_layers[i].mnt == path->layer->mnt)
-			break;
-	}
+	if (ovl_check_origin_xattr(upper))
+		return 0;
+
+	err = ovl_want_write(dentry);
+	if (err)
+		return err;
+
+	err = ovl_set_origin(dentry, lower, upper);
+	if (!err)
+		err = ovl_set_impure(dentry->d_parent, upper->d_parent);
 
-	return i;
+	ovl_drop_write(dentry);
+	return err;
 }
 
 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
@@ -594,6 +801,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
 	struct ovl_path *stack = NULL;
 	struct dentry *upperdir, *upperdentry = NULL;
+	struct dentry *origin = NULL;
 	struct dentry *index = NULL;
 	unsigned int ctr = 0;
 	struct inode *inode = NULL;
@@ -638,8 +846,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			 * number - it's the same as if we held a reference
 			 * to a dentry in lower layer that was moved under us.
 			 */
-			err = ovl_check_origin(upperdentry, roe->lowerstack,
-					       roe->numlower, &stack, &ctr);
+			err = ovl_check_origin(ofs, upperdentry, &stack, &ctr);
 			if (err)
 				goto out_put_upper;
 		}
@@ -674,6 +881,34 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		if (!this)
 			continue;
 
+		/*
+		 * If no origin fh is stored in upper of a merge dir, store fh
+		 * of lower dir and set upper parent "impure".
+		 */
+		if (upperdentry && !ctr && !ofs->noxattr) {
+			err = ovl_fix_origin(dentry, this, upperdentry);
+			if (err) {
+				dput(this);
+				goto out_put;
+			}
+		}
+
+		/*
+		 * When "verify_lower" feature is enabled, do not merge with a
+		 * lower dir that does not match a stored origin xattr. In any
+		 * case, only verified origin is used for index lookup.
+		 */
+		if (upperdentry && !ctr && ovl_verify_lower(dentry->d_sb)) {
+			err = ovl_verify_origin(upperdentry, this, false);
+			if (err) {
+				dput(this);
+				break;
+			}
+
+			/* Bless lower dir as verified origin */
+			origin = this;
+		}
+
 		stack[ctr].dentry = this;
 		stack[ctr].layer = lower.layer;
 		ctr++;
@@ -693,25 +928,30 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		 */
 		err = -EPERM;
 		if (d.redirect && !ofs->config.redirect_follow) {
-			pr_warn_ratelimited("overlay: refusing to follow redirect for (%pd2)\n", dentry);
+			pr_warn_ratelimited("overlayfs: refusing to follow redirect for (%pd2)\n",
+					    dentry);
 			goto out_put;
 		}
 
 		if (d.redirect && d.redirect[0] == '/' && poe != roe) {
 			poe = roe;
-
 			/* Find the current layer on the root dentry */
-			i = ovl_find_layer(ofs, &lower);
-			if (WARN_ON(i == ofs->numlower))
-				break;
+			i = lower.layer->idx - 1;
 		}
 	}
 
-	/* Lookup index by lower inode and verify it matches upper inode */
-	if (ctr && !d.is_dir && ovl_indexdir(dentry->d_sb)) {
-		struct dentry *origin = stack[0].dentry;
+	/*
+	 * Lookup index by lower inode and verify it matches upper inode.
+	 * We only trust dir index if we verified that lower dir matches
+	 * origin, otherwise dir index entries may be inconsistent and we
+	 * ignore them. Always lookup index of non-dir and non-upper.
+	 */
+	if (ctr && (!upperdentry || !d.is_dir))
+		origin = stack[0].dentry;
 
-		index = ovl_lookup_index(dentry, upperdentry, origin);
+	if (origin && ovl_indexdir(dentry->d_sb) &&
+	    (!d.is_dir || ovl_index_all(dentry->d_sb))) {
+		index = ovl_lookup_index(ofs, upperdentry, origin, true);
 		if (IS_ERR(index)) {
 			err = PTR_ERR(index);
 			index = NULL;
@@ -724,17 +964,22 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	if (!oe)
 		goto out_put;
 
-	oe->opaque = upperopaque;
 	memcpy(oe->lowerstack, stack, sizeof(struct ovl_path) * ctr);
 	dentry->d_fsdata = oe;
 
+	if (upperopaque)
+		ovl_dentry_set_opaque(dentry);
+
 	if (upperdentry)
 		ovl_dentry_set_upper_alias(dentry);
 	else if (index)
 		upperdentry = dget(index);
 
 	if (upperdentry || ctr) {
-		inode = ovl_get_inode(dentry, upperdentry, index);
+		if (ctr)
+			origin = stack[0].dentry;
+		inode = ovl_get_inode(dentry->d_sb, upperdentry, origin, index,
+				      ctr);
 		err = PTR_ERR(inode);
 		if (IS_ERR(inode))
 			goto out_free_oe;
@@ -748,9 +993,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	dput(index);
 	kfree(stack);
 	kfree(d.redirect);
-	d_add(dentry, inode);
-
-	return NULL;
+	return d_splice_alias(inode, dentry);
 
 out_free_oe:
 	dentry->d_fsdata = NULL;
@@ -771,9 +1014,9 @@ out:
 
 bool ovl_lower_positive(struct dentry *dentry)
 {
-	struct ovl_entry *oe = dentry->d_fsdata;
 	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
 	const struct qstr *name = &dentry->d_name;
+	const struct cred *old_cred;
 	unsigned int i;
 	bool positive = false;
 	bool done = false;
@@ -783,12 +1026,13 @@ bool ovl_lower_positive(struct dentry *dentry)
 	 * whiteout.
 	 */
 	if (!dentry->d_inode)
-		return oe->opaque;
+		return ovl_dentry_is_opaque(dentry);
 
 	/* Negative upper -> positive lower */
 	if (!ovl_dentry_upper(dentry))
 		return true;
 
+	old_cred = ovl_override_creds(dentry->d_sb);
 	/* Positive upper -> have to look up lower to see whether it exists */
 	for (i = 0; !done && !positive && i < poe->numlower; i++) {
 		struct dentry *this;
@@ -818,6 +1062,7 @@ bool ovl_lower_positive(struct dentry *dentry)
 			dput(this);
 		}
 	}
+	revert_creds(old_cred);
 
 	return positive;
 }