Merge tag 'ovl-update-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "Fixes:

   - Resolve mount option conflicts consistently

   - Sync before remount R/O

   - Fix file handle encoding corner cases

   - Fix metacopy related issues

   - Fix an unintialized return value

   - Add missing permission checks for underlying layers

  Optimizations:

   - Allow multipe whiteouts to share an inode

   - Optimize small writes by inheriting SB_NOSEC from upper layer

   - Do not call ->syncfs() multiple times for sync(2)

   - Do not cache negative lookups on upper layer

   - Make private internal mounts longterm"

* tag 'ovl-update-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (27 commits)
  ovl: remove unnecessary lock check
  ovl: make oip->index bool
  ovl: only pass ->ki_flags to ovl_iocb_to_rwf()
  ovl: make private mounts longterm
  ovl: get rid of redundant members in struct ovl_fs
  ovl: add accessor for ofs->upper_mnt
  ovl: initialize error in ovl_copy_xattr
  ovl: drop negative dentry in upper layer
  ovl: check permission to open real file
  ovl: call secutiry hook in ovl_real_ioctl()
  ovl: verify permissions in ovl_path_open()
  ovl: switch to mounter creds in readdir
  ovl: pass correct flags for opening real directory
  ovl: fix redirect traversal on metacopy dentries
  ovl: initialize OVL_UPPERDATA in ovl_lookup()
  ovl: use only uppermetacopy state in ovl_lookup()
  ovl: simplify setting of origin for index lookup
  ovl: fix out of bounds access warning in ovl_check_fb_len()
  ovl: return required buffer size for file handles
  ovl: sync dirty data when remounting to ro mode
  ...

13 files changed, 423 insertions, 220 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 6d499ab254b7..7cd642409165 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1937,6 +1937,9 @@ struct vfsmount *clone_private_mount(const struct path *path)
 	if (IS_ERR(new_mnt))
 		return ERR_CAST(new_mnt);
 
+	/* Longterm mount to be removed by kern_unmount*() */
+	new_mnt->mnt_ns = MNT_NS_INTERNAL;
+
 	return &new_mnt->mnt;
 }
 EXPORT_SYMBOL_GPL(clone_private_mount);
@@ -3863,6 +3866,19 @@ void kern_unmount(struct vfsmount *mnt)
 }
 EXPORT_SYMBOL(kern_unmount);
 
+void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (mnt[i])
+			real_mount(mnt[i])->mnt_ns = NULL;
+	synchronize_rcu_expedited();
+	for (i = 0; i < num; i++)
+		mntput(mnt[i]);
+}
+EXPORT_SYMBOL(kern_unmount_array);
+
 bool our_mnt(struct vfsmount *mnt)
 {
 	return check_mnt(real_mount(mnt));
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 9709cf22cab3..79dd052c7dbf 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -47,7 +47,7 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 {
 	ssize_t list_size, size, value_size = 0;
 	char *buf, *name, *value = NULL;
-	int uninitialized_var(error);
+	int error = 0;
 	size_t slen;
 
 	if (!(old->d_inode->i_opflags & IOP_XATTR) ||
@@ -584,9 +584,10 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
 		.link = c->link
 	};
 
-	err = ovl_lock_rename_workdir(c->workdir, c->destdir);
-	if (err)
-		return err;
+	/* workdir and destdir could be the same when copying up to indexdir */
+	err = -EIO;
+	if (lock_rename(c->workdir, c->destdir) != NULL)
+		goto unlock;
 
 	err = ovl_prep_cu_creds(c->dentry, &cc);
 	if (err)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 279009dee366..1bba4813f9cb 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -62,35 +62,59 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
 }
 
 /* caller holds i_mutex on workdir */
-static struct dentry *ovl_whiteout(struct dentry *workdir)
+static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
 {
 	int err;
 	struct dentry *whiteout;
+	struct dentry *workdir = ofs->workdir;
 	struct inode *wdir = workdir->d_inode;
 
-	whiteout = ovl_lookup_temp(workdir);
-	if (IS_ERR(whiteout))
-		return whiteout;
+	if (!ofs->whiteout) {
+		whiteout = ovl_lookup_temp(workdir);
+		if (IS_ERR(whiteout))
+			goto out;
 
-	err = ovl_do_whiteout(wdir, whiteout);
-	if (err) {
-		dput(whiteout);
-		whiteout = ERR_PTR(err);
+		err = ovl_do_whiteout(wdir, whiteout);
+		if (err) {
+			dput(whiteout);
+			whiteout = ERR_PTR(err);
+			goto out;
+		}
+		ofs->whiteout = whiteout;
 	}
 
+	if (ofs->share_whiteout) {
+		whiteout = ovl_lookup_temp(workdir);
+		if (IS_ERR(whiteout))
+			goto out;
+
+		err = ovl_do_link(ofs->whiteout, wdir, whiteout);
+		if (!err)
+			goto out;
+
+		if (err != -EMLINK) {
+			pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
+				ofs->whiteout->d_inode->i_nlink, err);
+			ofs->share_whiteout = false;
+		}
+		dput(whiteout);
+	}
+	whiteout = ofs->whiteout;
+	ofs->whiteout = NULL;
+out:
 	return whiteout;
 }
 
 /* Caller must hold i_mutex on both workdir and dir */
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
 			     struct dentry *dentry)
 {
-	struct inode *wdir = workdir->d_inode;
+	struct inode *wdir = ofs->workdir->d_inode;
 	struct dentry *whiteout;
 	int err;
 	int flags = 0;
 
-	whiteout = ovl_whiteout(workdir);
+	whiteout = ovl_whiteout(ofs);
 	err = PTR_ERR(whiteout);
 	if (IS_ERR(whiteout))
 		return err;
@@ -262,6 +286,8 @@ static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
 		inode = ovl_get_inode(dentry->d_sb, &oip);
 		if (IS_ERR(inode))
 			return PTR_ERR(inode);
+		if (inode == oip.newinode)
+			ovl_set_flag(OVL_UPPERDATA, inode);
 	} else {
 		WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
 		dput(newdentry);
@@ -715,6 +741,7 @@ static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
 static int ovl_remove_and_whiteout(struct dentry *dentry,
 				   struct list_head *list)
 {
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *workdir = ovl_workdir(dentry);
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct dentry *upper;
@@ -748,7 +775,7 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
 		goto out_dput_upper;
 	}
 
-	err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
+	err = ovl_cleanup_and_whiteout(ofs, d_inode(upperdir), upper);
 	if (err)
 		goto out_d_drop;
 
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index ed5c1078919c..8f4286450f92 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -204,7 +204,7 @@ static int ovl_check_encode_origin(struct dentry *dentry)
 	 * ovl_connect_layer() will try to make origin's layer "connected" by
 	 * copying up a "connectable" ancestor.
 	 */
-	if (d_is_dir(dentry) && ofs->upper_mnt)
+	if (d_is_dir(dentry) && ovl_upper_mnt(ofs))
 		return ovl_connect_layer(dentry);
 
 	/* Lower file handle for indexed and non-upper dir/non-dir */
@@ -231,12 +231,9 @@ static int ovl_dentry_to_fid(struct dentry *dentry, u32 *fid, int buflen)
 	if (IS_ERR(fh))
 		return PTR_ERR(fh);
 
-	err = -EOVERFLOW;
 	len = OVL_FH_LEN(fh);
-	if (len > buflen)
-		goto fail;
-
-	memcpy(fid, fh, len);
+	if (len <= buflen)
+		memcpy(fid, fh, len);
 	err = len;
 
 out:
@@ -244,9 +241,8 @@ out:
 	return err;
 
 fail:
-	pr_warn_ratelimited("failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n",
-			    dentry, err, buflen, fh ? (int)fh->fb.len : 0,
-			    fh ? fh->fb.type : 0);
+	pr_warn_ratelimited("failed to encode file handle (%pd2, err=%i)\n",
+			    dentry, err);
 	goto out;
 }
 
@@ -254,7 +250,7 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
 			 struct inode *parent)
 {
 	struct dentry *dentry;
-	int bytes = *max_len << 2;
+	int bytes, buflen = *max_len << 2;
 
 	/* TODO: encode connectable file handles */
 	if (parent)
@@ -264,12 +260,14 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
 	if (WARN_ON(!dentry))
 		return FILEID_INVALID;
 
-	bytes = ovl_dentry_to_fid(dentry, fid, bytes);
+	bytes = ovl_dentry_to_fid(dentry, fid, buflen);
 	dput(dentry);
 	if (bytes <= 0)
 		return FILEID_INVALID;
 
 	*max_len = bytes >> 2;
+	if (bytes > buflen)
+		return FILEID_INVALID;
 
 	return OVL_FILEID_V1;
 }
@@ -679,10 +677,10 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
 	struct dentry *dentry;
 	struct dentry *upper;
 
-	if (!ofs->upper_mnt)
+	if (!ovl_upper_mnt(ofs))
 		return ERR_PTR(-EACCES);
 
-	upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);
+	upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true);
 	if (IS_ERR_OR_NULL(upper))
 		return upper;
 
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 87c362f65448..01820e654a21 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -10,6 +10,7 @@
 #include <linux/uio.h>
 #include <linux/uaccess.h>
 #include <linux/splice.h>
+#include <linux/security.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include "overlayfs.h"
@@ -39,10 +40,22 @@ static struct file *ovl_open_realfile(const struct file *file,
 	struct file *realfile;
 	const struct cred *old_cred;
 	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
+	int acc_mode = ACC_MODE(flags);
+	int err;
+
+	if (flags & O_APPEND)
+		acc_mode |= MAY_APPEND;
 
 	old_cred = ovl_override_creds(inode->i_sb);
-	realfile = open_with_fake_path(&file->f_path, flags, realinode,
-				       current_cred());
+	err = inode_permission(realinode, MAY_OPEN | acc_mode);
+	if (err) {
+		realfile = ERR_PTR(err);
+	} else if (!inode_owner_or_capable(realinode)) {
+		realfile = ERR_PTR(-EPERM);
+	} else {
+		realfile = open_with_fake_path(&file->f_path, flags, realinode,
+					       current_cred());
+	}
 	revert_creds(old_cred);
 
 	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
@@ -219,9 +232,8 @@ static void ovl_file_accessed(struct file *file)
 	touch_atime(&file->f_path);
 }
 
-static rwf_t ovl_iocb_to_rwf(struct kiocb *iocb)
+static rwf_t ovl_iocb_to_rwf(int ifl)
 {
-	int ifl = iocb->ki_flags;
 	rwf_t flags = 0;
 
 	if (ifl & IOCB_NOWAIT)
@@ -283,7 +295,7 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	if (is_sync_kiocb(iocb)) {
 		ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
-				    ovl_iocb_to_rwf(iocb));
+				    ovl_iocb_to_rwf(iocb->ki_flags));
 	} else {
 		struct ovl_aio_req *aio_req;
 
@@ -336,7 +348,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	if (is_sync_kiocb(iocb)) {
 		file_start_write(real.file);
 		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
-				     ovl_iocb_to_rwf(iocb));
+				     ovl_iocb_to_rwf(iocb->ki_flags));
 		file_end_write(real.file);
 		/* Update size */
 		ovl_copyattr(ovl_inode_real(inode), inode);
@@ -520,7 +532,9 @@ static long ovl_real_ioctl(struct file *file, unsigned int cmd,
 		return ret;
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
-	ret = vfs_ioctl(real.file, cmd, arg);
+	ret = security_file_ioctl(real.file, cmd, arg);
+	if (!ret)
+		ret = vfs_ioctl(real.file, cmd, arg);
 	revert_creds(old_cred);
 
 	fdput(real);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 7af76b9004eb..8be6cd264f66 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -457,7 +457,7 @@ int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
 	if (flags & S_ATIME) {
 		struct ovl_fs *ofs = inode->i_sb->s_fs_info;
 		struct path upperpath = {
-			.mnt = ofs->upper_mnt,
+			.mnt = ovl_upper_mnt(ofs),
 			.dentry = ovl_upperdentry_dereference(OVL_I(inode)),
 		};
 
@@ -905,7 +905,7 @@ struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
  * Does overlay inode need to be hashed by lower inode?
  */
 static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
-			     struct dentry *lower, struct dentry *index)
+			     struct dentry *lower, bool index)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
 
@@ -918,7 +918,7 @@ static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
 		return true;
 
 	/* Yes, if won't be copied up */
-	if (!ofs->upper_mnt)
+	if (!ovl_upper_mnt(ofs))
 		return true;
 
 	/* No, if lower hardlink is or will be broken on copy up */
@@ -954,7 +954,7 @@ struct inode *ovl_get_inode(struct super_block *sb,
 	bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry,
 					oip->index);
 	int fsid = bylower ? lowerpath->layer->fsid : 0;
-	bool is_dir, metacopy = false;
+	bool is_dir;
 	unsigned long ino = 0;
 	int err = oip->newinode ? -EEXIST : -ENOMEM;
 
@@ -1015,15 +1015,6 @@ struct inode *ovl_get_inode(struct super_block *sb,
 	if (oip->index)
 		ovl_set_flag(OVL_INDEX, inode);
 
-	if (upperdentry) {
-		err = ovl_check_metacopy_xattr(upperdentry);
-		if (err < 0)
-			goto out_err;
-		metacopy = err;
-		if (!metacopy)
-			ovl_set_flag(OVL_UPPERDATA, inode);
-	}
-
 	OVL_I(inode)->redirect = oip->redirect;
 
 	if (bylower)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 0db23baf98e7..3566282a9199 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -191,16 +191,36 @@ static bool ovl_is_opaquedir(struct dentry *dentry)
 	return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE);
 }
 
+static struct dentry *ovl_lookup_positive_unlocked(const char *name,
+						   struct dentry *base, int len,
+						   bool drop_negative)
+{
+	struct dentry *ret = lookup_one_len_unlocked(name, base, len);
+
+	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
+		if (drop_negative && ret->d_lockref.count == 1) {
+			spin_lock(&ret->d_lock);
+			/* Recheck condition under lock */
+			if (d_is_negative(ret) && ret->d_lockref.count == 1)
+				__d_drop(ret);
+			spin_unlock(&ret->d_lock);
+		}
+		dput(ret);
+		ret = ERR_PTR(-ENOENT);
+	}
+	return ret;
+}
+
 static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
 			     const char *name, unsigned int namelen,
 			     size_t prelen, const char *post,
-			     struct dentry **ret)
+			     struct dentry **ret, bool drop_negative)
 {
 	struct dentry *this;
 	int err;
 	bool last_element = !post[0];
 
-	this = lookup_positive_unlocked(name, base, namelen);
+	this = ovl_lookup_positive_unlocked(name, base, namelen, drop_negative);
 	if (IS_ERR(this)) {
 		err = PTR_ERR(this);
 		this = NULL;
@@ -276,7 +296,7 @@ out_err:
 }
 
 static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
-			    struct dentry **ret)
+			    struct dentry **ret, bool drop_negative)
 {
 	/* Counting down from the end, since the prefix can change */
 	size_t rem = d->name.len - 1;
@@ -285,7 +305,7 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 
 	if (d->name.name[0] != '/')
 		return ovl_lookup_single(base, d, d->name.name, d->name.len,
-					 0, "", ret);
+					 0, "", ret, drop_negative);
 
 	while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
 		const char *s = d->name.name + d->name.len - rem;
@@ -298,7 +318,8 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 			return -EIO;
 
 		err = ovl_lookup_single(base, d, s, thislen,
-					d->name.len - rem, next, &base);
+					d->name.len - rem, next, &base,
+					drop_negative);
 		dput(dentry);
 		if (err)
 			return err;
@@ -468,7 +489,7 @@ struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
 	if (IS_ERR_OR_NULL(fh))
 		return ERR_CAST(fh);
 
-	upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);
+	upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true);
 	kfree(fh);
 
 	if (IS_ERR_OR_NULL(upper))
@@ -484,12 +505,6 @@ struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
 	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.
@@ -507,11 +522,6 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
 	if (!d_inode(index))
 		return 0;
 
-	/* 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_fb)*2)
 		goto fail;
@@ -823,7 +833,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	struct dentry *this;
 	unsigned int i;
 	int err;
-	bool metacopy = false;
+	bool uppermetacopy = false;
 	struct ovl_lookup_data d = {
 		.sb = dentry->d_sb,
 		.name = dentry->d_name,
@@ -841,7 +851,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	old_cred = ovl_override_creds(dentry->d_sb);
 	upperdir = ovl_dentry_upper(dentry->d_parent);
 	if (upperdir) {
-		err = ovl_lookup_layer(upperdir, &d, &upperdentry);
+		err = ovl_lookup_layer(upperdir, &d, &upperdentry, true);
 		if (err)
 			goto out;
 
@@ -869,7 +879,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 				goto out_put_upper;
 
 			if (d.metacopy)
-				metacopy = true;
+				uppermetacopy = true;
 		}
 
 		if (d.redirect) {
@@ -899,13 +909,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		else
 			d.last = lower.layer->idx == roe->numlower;
 
-		err = ovl_lookup_layer(lower.dentry, &d, &this);
+		err = ovl_lookup_layer(lower.dentry, &d, &this, false);
 		if (err)
 			goto out_put;
 
 		if (!this)
 			continue;
 
+		if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) {
+			err = -EPERM;
+			pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n", dentry);
+			goto out_put;
+		}
+
 		/*
 		 * If no origin fh is stored in upper of a merge dir, store fh
 		 * of lower dir and set upper parent "impure".
@@ -940,21 +956,21 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			origin = this;
 		}
 
-		if (d.metacopy)
-			metacopy = true;
-		/*
-		 * Do not store intermediate metacopy dentries in chain,
-		 * except top most lower metacopy dentry
-		 */
 		if (d.metacopy && ctr) {
+			/*
+			 * Do not store intermediate metacopy dentries in
+			 * lower chain, except top most lower metacopy dentry.
+			 * Continue the loop so that if there is an absolute
+			 * redirect on this dentry, poe can be reset to roe.
+			 */
 			dput(this);
-			continue;
+			this = NULL;
+		} else {
+			stack[ctr].dentry = this;
+			stack[ctr].layer = lower.layer;
+			ctr++;
 		}
 
-		stack[ctr].dentry = this;
-		stack[ctr].layer = lower.layer;
-		ctr++;
-
 		/*
 		 * Following redirects can have security consequences: it's like
 		 * a symlink into the lower layer without the permission checks.
@@ -982,22 +998,17 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		}
 	}
 
-	if (metacopy) {
-		/*
-		 * Found a metacopy dentry but did not find corresponding
-		 * data dentry
-		 */
-		if (d.metacopy) {
-			err = -EIO;
-			goto out_put;
-		}
-
-		err = -EPERM;
-		if (!ofs->config.metacopy) {
-			pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n",
-					    dentry);
-			goto out_put;
-		}
+	/*
+	 * For regular non-metacopy upper dentries, there is no lower
+	 * path based lookup, hence ctr will be zero. If a dentry is found
+	 * using ORIGIN xattr on upper, install it in stack.
+	 *
+	 * For metacopy dentry, path based lookup will find lower dentries.
+	 * Just make sure a corresponding data dentry has been found.
+	 */
+	if (d.metacopy || (uppermetacopy && !ctr)) {
+		err = -EIO;
+		goto out_put;
 	} else if (!d.is_dir && upperdentry && !ctr && origin_path) {
 		if (WARN_ON(stack != NULL)) {
 			err = -EIO;
@@ -1005,25 +1016,30 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		}
 		stack = origin_path;
 		ctr = 1;
+		origin = origin_path->dentry;
 		origin_path = NULL;
 	}
 
 	/*
-	 * 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 if there is no-upperdentry.
+	 *
+	 * For the case of upperdentry, we have set origin by now if it
+	 * needed to be set. There are basically three cases.
+	 *
+	 * For directories, 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.
+	 *
+	 * For regular upper, we already set origin if upper had ORIGIN
+	 * xattr. There is no verification though as there is no path
+	 * based dentry lookup in lower in this case.
 	 *
-	 * For non-dir upper metacopy dentry, we already set "origin" if we
-	 * verified that lower matched upper origin. If upper origin was
-	 * not present (because lower layer did not support fh encode/decode),
-	 * or indexing is not enabled, do not set "origin" and skip looking up
-	 * index. This case should be handled in same way as a non-dir upper
-	 * without ORIGIN is handled.
+	 * For metacopy upper, we set a verified origin already if index
+	 * is enabled and if upper had an ORIGIN xattr.
 	 *
-	 * Always lookup index of non-dir non-metacopy and non-upper.
 	 */
-	if (ctr && (!upperdentry || (!d.is_dir && !metacopy)))
+	if (!upperdentry && ctr)
 		origin = stack[0].dentry;
 
 	if (origin && ovl_indexdir(dentry->d_sb) &&
@@ -1074,6 +1090,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		err = PTR_ERR(inode);
 		if (IS_ERR(inode))
 			goto out_free_oe;
+		if (upperdentry && !uppermetacopy)
+			ovl_set_flag(OVL_UPPERDATA, inode);
 	}
 
 	ovl_dentry_update_reval(dentry, upperdentry,
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index e6f3670146ed..b725c7f15ff4 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -355,6 +355,9 @@ int ovl_check_fb_len(struct ovl_fb *fb, int fb_len);
 
 static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
 {
+	if (fh_len < sizeof(struct ovl_fh))
+		return -EINVAL;
+
 	return ovl_check_fb_len(&fh->fb, fh_len - OVL_FH_WIRE_OFFSET);
 }
 
@@ -394,8 +397,8 @@ void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
 void ovl_cache_free(struct list_head *list);
 void ovl_dir_cache_free(struct inode *inode);
 int ovl_check_d_type_supported(struct path *realpath);
-void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
-			 struct dentry *dentry, int level);
+int ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
+			struct dentry *dentry, int level);
 int ovl_indexdir_cleanup(struct ovl_fs *ofs);
 
 /* inode.c */
@@ -421,7 +424,7 @@ struct ovl_inode_params {
 	struct inode *newinode;
 	struct dentry *upperdentry;
 	struct ovl_path *lowerpath;
-	struct dentry *index;
+	bool index;
 	unsigned int numlower;
 	char *redirect;
 	struct dentry *lowerdata;
@@ -455,7 +458,7 @@ static inline void ovl_copyflags(struct inode *from, struct inode *to)
 
 /* dir.c */
 extern const struct inode_operations ovl_dir_inode_operations;
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
 			     struct dentry *dentry);
 struct ovl_cattr {
 	dev_t rdev;
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 5762d802fe01..b429c80879ee 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -46,7 +46,6 @@ struct ovl_path {
 
 /* private information held for overlayfs's superblock */
 struct ovl_fs {
-	struct vfsmount *upper_mnt;
 	unsigned int numlayer;
 	/* Number of unique fs among layers including upper fs */
 	unsigned int numfs;
@@ -68,8 +67,8 @@ struct ovl_fs {
 	/* Did we take the inuse lock? */
 	bool upperdir_locked;
 	bool workdir_locked;
+	bool share_whiteout;
 	/* Traps in ovl inode cache */
-	struct inode *upperdir_trap;
 	struct inode *workbasedir_trap;
 	struct inode *workdir_trap;
 	struct inode *indexdir_trap;
@@ -77,8 +76,15 @@ struct ovl_fs {
 	int xino_mode;
 	/* For allocation of non-persistent inode numbers */
 	atomic_long_t last_ino;
+	/* Whiteout dentry cache */
+	struct dentry *whiteout;
 };
 
+static inline struct vfsmount *ovl_upper_mnt(struct ovl_fs *ofs)
+{
+	return ofs->layers[0].mnt;
+}
+
 static inline struct ovl_fs *OVL_FS(struct super_block *sb)
 {
 	return (struct ovl_fs *)sb->s_fs_info;
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index e452ff7d583d..6918b98faeb6 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -297,7 +297,7 @@ static inline int ovl_dir_read(struct path *realpath,
 	struct file *realfile;
 	int err;
 
-	realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY);
+	realfile = ovl_path_open(realpath, O_RDONLY | O_LARGEFILE);
 	if (IS_ERR(realfile))
 		return PTR_ERR(realfile);
 
@@ -743,8 +743,10 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
 	struct ovl_dir_file *od = file->private_data;
 	struct dentry *dentry = file->f_path.dentry;
 	struct ovl_cache_entry *p;
+	const struct cred *old_cred;
 	int err;
 
+	old_cred = ovl_override_creds(dentry->d_sb);
 	if (!ctx->pos)
 		ovl_dir_reset(file);
 
@@ -758,17 +760,20 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
 		    (ovl_same_fs(dentry->d_sb) &&
 		     (ovl_is_impure_dir(file) ||
 		      OVL_TYPE_MERGE(ovl_path_type(dentry->d_parent))))) {
-			return ovl_iterate_real(file, ctx);
+			err = ovl_iterate_real(file, ctx);
+		} else {
+			err = iterate_dir(od->realfile, ctx);
 		}
-		return iterate_dir(od->realfile, ctx);
+		goto out;
 	}
 
 	if (!od->cache) {
 		struct ovl_dir_cache *cache;
 
 		cache = ovl_cache_get(dentry);
+		err = PTR_ERR(cache);
 		if (IS_ERR(cache))
-			return PTR_ERR(cache);
+			goto out;
 
 		od->cache = cache;
 		ovl_seek_cursor(od, ctx->pos);
@@ -780,7 +785,7 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
 			if (!p->ino) {
 				err = ovl_cache_update_ino(&file->f_path, p);
 				if (err)
-					return err;
+					goto out;
 			}
 			if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
 				break;
@@ -788,7 +793,10 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
 		od->cursor = p->l_node.next;
 		ctx->pos++;
 	}
-	return 0;
+	err = 0;
+out:
+	revert_creds(old_cred);
+	return err;
 }
 
 static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
@@ -831,6 +839,19 @@ out_unlock:
 	return res;
 }
 
+static struct file *ovl_dir_open_realfile(struct file *file,
+					  struct path *realpath)
+{
+	struct file *res;
+	const struct cred *old_cred;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	res = ovl_path_open(realpath, O_RDONLY | (file->f_flags & O_LARGEFILE));
+	revert_creds(old_cred);
+
+	return res;
+}
+
 static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
 			 int datasync)
 {
@@ -853,7 +874,7 @@ static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
 			struct path upperpath;
 
 			ovl_path_upper(dentry, &upperpath);
-			realfile = ovl_path_open(&upperpath, O_RDONLY);
+			realfile = ovl_dir_open_realfile(file, &upperpath);
 
 			inode_lock(inode);
 			if (!od->upperfile) {
@@ -904,7 +925,7 @@ static int ovl_dir_open(struct inode *inode, struct file *file)
 		return -ENOMEM;
 
 	type = ovl_path_real(file->f_path.dentry, &realpath);
-	realfile = ovl_path_open(&realpath, file->f_flags);
+	realfile = ovl_dir_open_realfile(file, &realpath);
 	if (IS_ERR(realfile)) {
 		kfree(od);
 		return PTR_ERR(realfile);
@@ -1071,14 +1092,13 @@ out:
 	ovl_cache_free(&list);
 }
 
-void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
+int ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
 			 struct dentry *dentry, int level)
 {
 	int err;
 
 	if (!d_is_dir(dentry) || level > 1) {
-		ovl_cleanup(dir, dentry);
-		return;
+		return ovl_cleanup(dir, dentry);
 	}
 
 	err = ovl_do_rmdir(dir, dentry);
@@ -1088,8 +1108,10 @@ void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
 		inode_unlock(dir);
 		ovl_workdir_cleanup_recurse(&path, level + 1);
 		inode_lock_nested(dir, I_MUTEX_PARENT);
-		ovl_cleanup(dir, dentry);
+		err = ovl_cleanup(dir, dentry);
 	}
+
+	return err;
 }
 
 int ovl_indexdir_cleanup(struct ovl_fs *ofs)
@@ -1098,7 +1120,7 @@ int ovl_indexdir_cleanup(struct ovl_fs *ofs)
 	struct dentry *indexdir = ofs->indexdir;
 	struct dentry *index = NULL;
 	struct inode *dir = indexdir->d_inode;
-	struct path path = { .mnt = ofs->upper_mnt, .dentry = indexdir };
+	struct path path = { .mnt = ovl_upper_mnt(ofs), .dentry = indexdir };
 	LIST_HEAD(list);
 	struct rb_root root = RB_ROOT;
 	struct ovl_cache_entry *p;
@@ -1128,6 +1150,13 @@ int ovl_indexdir_cleanup(struct ovl_fs *ofs)
 			index = NULL;
 			break;
 		}
+		/* Cleanup leftover from index create/cleanup attempt */
+		if (index->d_name.name[0] == '#') {
+			err = ovl_workdir_cleanup(dir, path.mnt, index, 1);
+			if (err)
+				break;
+			goto next;
+		}
 		err = ovl_verify_index(ofs, index);
 		if (!err) {
 			goto next;
@@ -1146,7 +1175,7 @@ int ovl_indexdir_cleanup(struct ovl_fs *ofs)
 			 * Whiteout orphan index to block future open by
 			 * handle after overlay nlink dropped to zero.
 			 */
-			err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+			err = ovl_cleanup_and_whiteout(ofs, dir, index);
 		} else {
 			/* Cleanup orphan index entries */
 			err = ovl_cleanup(dir, index);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 732ad5495c92..91476bc422f9 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -211,24 +211,28 @@ static void ovl_destroy_inode(struct inode *inode)
 
 static void ovl_free_fs(struct ovl_fs *ofs)
 {
+	struct vfsmount **mounts;
 	unsigned i;
 
 	iput(ofs->workbasedir_trap);
 	iput(ofs->indexdir_trap);
 	iput(ofs->workdir_trap);
-	iput(ofs->upperdir_trap);
+	dput(ofs->whiteout);
 	dput(ofs->indexdir);
 	dput(ofs->workdir);
 	if (ofs->workdir_locked)
 		ovl_inuse_unlock(ofs->workbasedir);
 	dput(ofs->workbasedir);
 	if (ofs->upperdir_locked)
-		ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
-	mntput(ofs->upper_mnt);
-	for (i = 1; i < ofs->numlayer; i++) {
+		ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
+
+	/* Hack!  Reuse ofs->layers as a vfsmount array before freeing it */
+	mounts = (struct vfsmount **) ofs->layers;
+	for (i = 0; i < ofs->numlayer; i++) {
 		iput(ofs->layers[i].trap);
-		mntput(ofs->layers[i].mnt);
+		mounts[i] = ofs->layers[i].mnt;
 	}
+	kern_unmount_array(mounts, ofs->numlayer);
 	kfree(ofs->layers);
 	for (i = 0; i < ofs->numfs; i++)
 		free_anon_bdev(ofs->fs[i].pseudo_dev);
@@ -257,12 +261,12 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
 	struct super_block *upper_sb;
 	int ret;
 
-	if (!ofs->upper_mnt)
+	if (!ovl_upper_mnt(ofs))
 		return 0;
 
 	/*
-	 * If this is a sync(2) call or an emergency sync, all the super blocks
-	 * will be iterated, including upper_sb, so no need to do anything.
+	 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
+	 * All the super blocks will be iterated, including upper_sb.
 	 *
 	 * If this is a syncfs(2) call, then we do need to call
 	 * sync_filesystem() on upper_sb, but enough if we do it when being
@@ -271,7 +275,7 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
 	if (!wait)
 		return 0;
 
-	upper_sb = ofs->upper_mnt->mnt_sb;
+	upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 
 	down_read(&upper_sb->s_umount);
 	ret = sync_filesystem(upper_sb);
@@ -309,7 +313,7 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 /* Will this overlay be forced to mount/remount ro? */
 static bool ovl_force_readonly(struct ovl_fs *ofs)
 {
-	return (!ofs->upper_mnt || !ofs->workdir);
+	return (!ovl_upper_mnt(ofs) || !ofs->workdir);
 }
 
 static const char *ovl_redirect_mode_def(void)
@@ -364,11 +368,20 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
+	struct super_block *upper_sb;
+	int ret = 0;
 
 	if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
 		return -EROFS;
 
-	return 0;
+	if (*flags & SB_RDONLY && !sb_rdonly(sb)) {
+		upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+		down_read(&upper_sb->s_umount);
+		ret = sync_filesystem(upper_sb);
+		up_read(&upper_sb->s_umount);
+	}
+
+	return ret;
 }
 
 static const struct super_operations ovl_super_operations = {
@@ -470,6 +483,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 	char *p;
 	int err;
 	bool metacopy_opt = false, redirect_opt = false;
+	bool nfs_export_opt = false, index_opt = false;
 
 	config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
 	if (!config->redirect_mode)
@@ -519,18 +533,22 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 
 		case OPT_INDEX_ON:
 			config->index = true;
+			index_opt = true;
 			break;
 
 		case OPT_INDEX_OFF:
 			config->index = false;
+			index_opt = true;
 			break;
 
 		case OPT_NFS_EXPORT_ON:
 			config->nfs_export = true;
+			nfs_export_opt = true;
 			break;
 
 		case OPT_NFS_EXPORT_OFF:
 			config->nfs_export = false;
+			nfs_export_opt = true;
 			break;
 
 		case OPT_XINO_ON:
@@ -552,6 +570,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 
 		case OPT_METACOPY_OFF:
 			config->metacopy = false;
+			metacopy_opt = true;
 			break;
 
 		default:
@@ -601,6 +620,48 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 		}
 	}
 
+	/* Resolve nfs_export -> index dependency */
+	if (config->nfs_export && !config->index) {
+		if (nfs_export_opt && index_opt) {
+			pr_err("conflicting options: nfs_export=on,index=off\n");
+			return -EINVAL;
+		}
+		if (index_opt) {
+			/*
+			 * There was an explicit index=off that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling nfs_export due to index=off\n");
+			config->nfs_export = false;
+		} else {
+			/* Automatically enable index otherwise. */
+			config->index = true;
+		}
+	}
+
+	/* Resolve nfs_export -> !metacopy dependency */
+	if (config->nfs_export && config->metacopy) {
+		if (nfs_export_opt && metacopy_opt) {
+			pr_err("conflicting options: nfs_export=on,metacopy=on\n");
+			return -EINVAL;
+		}
+		if (metacopy_opt) {
+			/*
+			 * There was an explicit metacopy=on that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling nfs_export due to metacopy=on\n");
+			config->nfs_export = false;
+		} else {
+			/*
+			 * There was an explicit nfs_export=on that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling metacopy due to nfs_export=on\n");
+			config->metacopy = false;
+		}
+	}
+
 	return 0;
 }
 
@@ -611,15 +672,12 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 					 const char *name, bool persist)
 {
 	struct inode *dir =  ofs->workbasedir->d_inode;
-	struct vfsmount *mnt = ofs->upper_mnt;
+	struct vfsmount *mnt = ovl_upper_mnt(ofs);
 	struct dentry *work;
 	int err;
 	bool retried = false;
-	bool locked = false;
 
 	inode_lock_nested(dir, I_MUTEX_PARENT);
-	locked = true;
-
 retry:
 	work = lookup_one_len(name, ofs->workbasedir, strlen(name));
 
@@ -680,9 +738,7 @@ retry:
 		goto out_err;
 	}
 out_unlock:
-	if (locked)
-		inode_unlock(dir);
-
+	inode_unlock(dir);
 	return work;
 
 out_dput:
@@ -779,11 +835,11 @@ static int ovl_lower_dir(const char *name, struct path *path,
 
 	err = ovl_mount_dir_noesc(name, path);
 	if (err)
-		goto out;
+		return err;
 
 	err = ovl_check_namelen(path, ofs, name);
 	if (err)
-		goto out_put;
+		return err;
 
 	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 
@@ -805,11 +861,6 @@ static int ovl_lower_dir(const char *name, struct path *path,
 		ofs->xino_mode = -1;
 
 	return 0;
-
-out_put:
-	path_put_init(path);
-out:
-	return err;
 }
 
 /* Workdir should not be subdir of upperdir and vice versa */
@@ -1016,7 +1067,7 @@ static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
 }
 
 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
-			 struct path *upperpath)
+			 struct ovl_layer *upper_layer, struct path *upperpath)
 {
 	struct vfsmount *upper_mnt;
 	int err;
@@ -1036,7 +1087,7 @@ static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
 	if (err)
 		goto out;
 
-	err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
+	err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
 			     "upperdir");
 	if (err)
 		goto out;
@@ -1050,9 +1101,23 @@ static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
 
 	/* Don't inherit atime flags */
 	upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
-	ofs->upper_mnt = upper_mnt;
+	upper_layer->mnt = upper_mnt;
+	upper_layer->idx = 0;
+	upper_layer->fsid = 0;
 
-	if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
+	/*
+	 * Inherit SB_NOSEC flag from upperdir.
+	 *
+	 * This optimization changes behavior when a security related attribute
+	 * (suid/sgid/security.*) is changed on an underlying layer.  This is
+	 * okay because we don't yet have guarantees in that case, but it will
+	 * need careful treatment once we want to honour changes to underlying
+	 * filesystems.
+	 */
+	if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
+		sb->s_flags |= SB_NOSEC;
+
+	if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
 		ofs->upperdir_locked = true;
 	} else {
 		err = ovl_report_in_use(ofs, "upperdir");
@@ -1128,7 +1193,7 @@ out_unlock:
 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 			    struct path *workpath)
 {
-	struct vfsmount *mnt = ofs->upper_mnt;
+	struct vfsmount *mnt = ovl_upper_mnt(ofs);
 	struct dentry *temp;
 	bool rename_whiteout;
 	bool d_type;
@@ -1272,7 +1337,7 @@ out:
 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
 			    struct ovl_entry *oe, struct path *upperpath)
 {
-	struct vfsmount *mnt = ofs->upper_mnt;
+	struct vfsmount *mnt = ovl_upper_mnt(ofs);
 	int err;
 
 	err = mnt_want_write(mnt);
@@ -1328,7 +1393,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
 {
 	unsigned int i;
 
-	if (!ofs->config.nfs_export && !ofs->upper_mnt)
+	if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
 		return true;
 
 	for (i = 0; i < ofs->numfs; i++) {
@@ -1388,18 +1453,13 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
 }
 
 static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
-			  struct path *stack, unsigned int numlower)
+			  struct path *stack, unsigned int numlower,
+			  struct ovl_layer *layers)
 {
 	int err;
 	unsigned int i;
-	struct ovl_layer *layers;
 
 	err = -ENOMEM;
-	layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
-	if (!layers)
-		goto out;
-	ofs->layers = layers;
-
 	ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
 	if (ofs->fs == NULL)
 		goto out;
@@ -1407,11 +1467,6 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 	/* idx/fsid 0 are reserved for upper fs even with lower only overlay */
 	ofs->numfs++;
 
-	layers[0].mnt = ofs->upper_mnt;
-	layers[0].idx = 0;
-	layers[0].fsid = 0;
-	ofs->numlayer = 1;
-
 	/*
 	 * All lower layers that share the same fs as upper layer, use the same
 	 * pseudo_dev as upper layer.  Allocate fs[0].pseudo_dev even for lower
@@ -1424,8 +1479,8 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 		goto out;
 	}
 
-	if (ofs->upper_mnt) {
-		ofs->fs[0].sb = ofs->upper_mnt->mnt_sb;
+	if (ovl_upper_mnt(ofs)) {
+		ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
 		ofs->fs[0].is_lower = false;
 	}
 
@@ -1480,7 +1535,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 	 * inode number or a non persistent inode number allocated from a
 	 * dedicated range.
 	 */
-	if (ofs->numfs - !ofs->upper_mnt == 1) {
+	if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
 		if (ofs->config.xino == OVL_XINO_ON)
 			pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
 		ofs->xino_mode = 0;
@@ -1509,44 +1564,30 @@ out:
 }
 
 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
-					    struct ovl_fs *ofs)
+				const char *lower, unsigned int numlower,
+				struct ovl_fs *ofs, struct ovl_layer *layers)
 {
 	int err;
-	char *lowertmp, *lower;
 	struct path *stack = NULL;
-	unsigned int stacklen, numlower = 0, i;
+	unsigned int i;
 	struct ovl_entry *oe;
 
-	err = -ENOMEM;
-	lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
-	if (!lowertmp)
-		goto out_err;
-
-	err = -EINVAL;
-	stacklen = ovl_split_lowerdirs(lowertmp);
-	if (stacklen > OVL_MAX_STACK) {
-		pr_err("too many lower directories, limit is %d\n",
-		       OVL_MAX_STACK);
-		goto out_err;
-	} else if (!ofs->config.upperdir && stacklen == 1) {
+	if (!ofs->config.upperdir && numlower == 1) {
 		pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
-		goto out_err;
+		return ERR_PTR(-EINVAL);
 	} else if (!ofs->config.upperdir && ofs->config.nfs_export &&
 		   ofs->config.redirect_follow) {
 		pr_warn("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
 		ofs->config.nfs_export = false;
 	}
 
-	err = -ENOMEM;
-	stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
+	stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
 	if (!stack)
-		goto out_err;
+		return ERR_PTR(-ENOMEM);
 
 	err = -EINVAL;
-	lower = lowertmp;
-	for (numlower = 0; numlower < stacklen; numlower++) {
-		err = ovl_lower_dir(lower, &stack[numlower], ofs,
-				    &sb->s_stack_depth);
+	for (i = 0; i < numlower; i++) {
+		err = ovl_lower_dir(lower, &stack[i], ofs, &sb->s_stack_depth);
 		if (err)
 			goto out_err;
 
@@ -1560,7 +1601,7 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
 		goto out_err;
 	}
 
-	err = ovl_get_layers(sb, ofs, stack, numlower);
+	err = ovl_get_layers(sb, ofs, stack, numlower, layers);
 	if (err)
 		goto out_err;
 
@@ -1578,7 +1619,6 @@ out:
 	for (i = 0; i < numlower; i++)
 		path_put(&stack[i]);
 	kfree(stack);
-	kfree(lowertmp);
 
 	return oe;
 
@@ -1629,8 +1669,8 @@ static int ovl_check_overlapping_layers(struct super_block *sb,
 {
 	int i, err;
 
-	if (ofs->upper_mnt) {
-		err = ovl_check_layer(sb, ofs, ofs->upper_mnt->mnt_root,
+	if (ovl_upper_mnt(ofs)) {
+		err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
 				      "upperdir");
 		if (err)
 			return err;
@@ -1702,7 +1742,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	struct dentry *root_dentry;
 	struct ovl_entry *oe;
 	struct ovl_fs *ofs;
+	struct ovl_layer *layers;
 	struct cred *cred;
+	char *splitlower = NULL;
+	unsigned int numlower;
 	int err;
 
 	sb->s_d_op = &ovl_dentry_operations;
@@ -1716,6 +1759,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	if (!cred)
 		goto out_err;
 
+	/* Is there a reason anyone would want not to share whiteouts? */
+	ofs->share_whiteout = true;
+
 	ofs->config.index = ovl_index_def;
 	ofs->config.nfs_export = ovl_nfs_export_def;
 	ofs->config.xino = ovl_xino_def();
@@ -1731,6 +1777,26 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		goto out_err;
 	}
 
+	err = -ENOMEM;
+	splitlower = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
+	if (!splitlower)
+		goto out_err;
+
+	numlower = ovl_split_lowerdirs(splitlower);
+	if (numlower > OVL_MAX_STACK) {
+		pr_err("too many lower directories, limit is %d\n",
+		       OVL_MAX_STACK);
+		goto out_err;
+	}
+
+	layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
+	if (!layers)
+		goto out_err;
+
+	ofs->layers = layers;
+	/* Layer 0 is reserved for upper even if there's no upper */
+	ofs->numlayer = 1;
+
 	sb->s_stack_depth = 0;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	atomic_long_set(&ofs->last_ino, 1);
@@ -1752,7 +1818,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			goto out_err;
 		}
 
-		err = ovl_get_upper(sb, ofs, &upperpath);
+		err = ovl_get_upper(sb, ofs, &layers[0], &upperpath);
 		if (err)
 			goto out_err;
 
@@ -1763,31 +1829,35 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		if (!ofs->workdir)
 			sb->s_flags |= SB_RDONLY;
 
-		sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
-		sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
+		sb->s_stack_depth = ovl_upper_mnt(ofs)->mnt_sb->s_stack_depth;
+		sb->s_time_gran = ovl_upper_mnt(ofs)->mnt_sb->s_time_gran;
 
 	}
-	oe = ovl_get_lowerstack(sb, ofs);
+	oe = ovl_get_lowerstack(sb, splitlower, numlower, ofs, layers);
 	err = PTR_ERR(oe);
 	if (IS_ERR(oe))
 		goto out_err;
 
 	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
-	if (!ofs->upper_mnt)
+	if (!ovl_upper_mnt(ofs))
 		sb->s_flags |= SB_RDONLY;
 
 	if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
+		/* index dir will act also as workdir */
+		dput(ofs->workdir);
+		ofs->workdir = NULL;
+		iput(ofs->workdir_trap);
+		ofs->workdir_trap = NULL;
+
 		err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
 		if (err)
 			goto out_free_oe;
 
 		/* Force r/o mount with no index dir */
-		if (!ofs->indexdir) {
-			dput(ofs->workdir);
-			ofs->workdir = NULL;
+		if (ofs->indexdir)
+			ofs->workdir = dget(ofs->indexdir);
+		else
 			sb->s_flags |= SB_RDONLY;
-		}
-
 	}
 
 	err = ovl_check_overlapping_layers(sb, ofs);
@@ -1797,7 +1867,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	/* Show index=off in /proc/mounts for forced r/o mount */
 	if (!ofs->indexdir) {
 		ofs->config.index = false;
-		if (ofs->upper_mnt && ofs->config.nfs_export) {
+		if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
 			pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
 			ofs->config.nfs_export = false;
 		}
@@ -1818,6 +1888,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_xattr = ovl_xattr_handlers;
 	sb->s_fs_info = ofs;
 	sb->s_flags |= SB_POSIXACL;
+	sb->s_iflags |= SB_I_SKIP_SYNC;
 
 	err = -ENOMEM;
 	root_dentry = ovl_get_root(sb, upperpath.dentry, oe);
@@ -1825,6 +1896,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		goto out_free_oe;
 
 	mntput(upperpath.mnt);
+	kfree(splitlower);
 
 	sb->s_root = root_dentry;
 
@@ -1834,6 +1906,7 @@ out_free_oe:
 	ovl_entry_stack_free(oe);
 	kfree(oe);
 out_err:
+	kfree(splitlower);
 	path_put(&upperpath);
 	ovl_free_fs(ofs);
 out:
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 36b60788ee47..56c1f89f20c9 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -18,13 +18,13 @@
 int ovl_want_write(struct dentry *dentry)
 {
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	return mnt_want_write(ofs->upper_mnt);
+	return mnt_want_write(ovl_upper_mnt(ofs));
 }
 
 void ovl_drop_write(struct dentry *dentry)
 {
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	mnt_drop_write(ofs->upper_mnt);
+	mnt_drop_write(ovl_upper_mnt(ofs));
 }
 
 struct dentry *ovl_workdir(struct dentry *dentry)
@@ -150,7 +150,7 @@ void ovl_path_upper(struct dentry *dentry, struct path *path)
 {
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 
-	path->mnt = ofs->upper_mnt;
+	path->mnt = ovl_upper_mnt(ofs);
 	path->dentry = ovl_dentry_upper(dentry);
 }
 
@@ -459,7 +459,32 @@ bool ovl_is_whiteout(struct dentry *dentry)
 
 struct file *ovl_path_open(struct path *path, int flags)
 {
-	return dentry_open(path, flags | O_NOATIME, current_cred());
+	struct inode *inode = d_inode(path->dentry);
+	int err, acc_mode;
+
+	if (flags & ~(O_ACCMODE | O_LARGEFILE))
+		BUG();
+
+	switch (flags & O_ACCMODE) {
+	case O_RDONLY:
+		acc_mode = MAY_READ;
+		break;
+	case O_WRONLY:
+		acc_mode = MAY_WRITE;
+		break;
+	default:
+		BUG();
+	}
+
+	err = inode_permission(inode, acc_mode | MAY_OPEN);
+	if (err)
+		return ERR_PTR(err);
+
+	/* O_NOATIME is an optimization, don't fail if not permitted */
+	if (inode_owner_or_capable(inode))
+		flags |= O_NOATIME;
+
+	return dentry_open(path, flags, current_cred());
 }
 
 /* Caller should hold ovl_inode->lock */
@@ -707,7 +732,8 @@ static void ovl_cleanup_index(struct dentry *dentry)
 		index = NULL;
 	} else if (ovl_index_all(dentry->d_sb)) {
 		/* Whiteout orphan index to block future open by handle */
-		err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+		err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
+					       dir, index);
 	} else {
 		/* Cleanup orphan index entries */
 		err = ovl_cleanup(dir, index);
diff --git a/fs/sync.c b/fs/sync.c
index c6f6f5be5682..1373a610dc78 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -76,7 +76,8 @@ static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 
 static void sync_fs_one_sb(struct super_block *sb, void *arg)
 {
-	if (!sb_rdonly(sb) && sb->s_op->sync_fs)
+	if (!sb_rdonly(sb) && !(sb->s_iflags & SB_I_SKIP_SYNC) &&
+	    sb->s_op->sync_fs)
 		sb->s_op->sync_fs(sb, *(int *)arg);
 }