selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 1291 insertions, 0 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
new file mode 100644
index 000000000..e963701b4
--- /dev/null
+++ b/fs/overlayfs/copy_up.c
@@ -0,0 +1,1291 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/fileattr.h>
+#include <linux/splice.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
+#include <linux/uaccess.h>
+#include <linux/sched/signal.h>
+#include <linux/cred.h>
+#include <linux/namei.h>
+#include <linux/ratelimit.h>
+#include <linux/exportfs.h>
+#include "overlayfs.h"
+
+#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
+
+static int ovl_ccup_set(const char *buf, const struct kernel_param *param)
+{
+	pr_warn("\"check_copy_up\" module option is obsolete\n");
+	return 0;
+}
+
+static int ovl_ccup_get(char *buf, const struct kernel_param *param)
+{
+	return sprintf(buf, "N\n");
+}
+
+module_param_call(check_copy_up, ovl_ccup_set, ovl_ccup_get, NULL, 0644);
+MODULE_PARM_DESC(check_copy_up, "Obsolete; does nothing");
+
+static bool ovl_must_copy_xattr(const char *name)
+{
+	return !strcmp(name, XATTR_POSIX_ACL_ACCESS) ||
+	       !strcmp(name, XATTR_POSIX_ACL_DEFAULT) ||
+	       !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN);
+}
+
+static int ovl_copy_acl(struct ovl_fs *ofs, const struct path *path,
+			struct dentry *dentry, const char *acl_name)
+{
+	int err;
+	struct posix_acl *clone, *real_acl = NULL;
+
+	real_acl = ovl_get_acl_path(path, acl_name, false);
+	if (!real_acl)
+		return 0;
+
+	if (IS_ERR(real_acl)) {
+		err = PTR_ERR(real_acl);
+		if (err == -ENODATA || err == -EOPNOTSUPP)
+			return 0;
+		return err;
+	}
+
+	clone = posix_acl_clone(real_acl, GFP_KERNEL);
+	posix_acl_release(real_acl); /* release original acl */
+	if (!clone)
+		return -ENOMEM;
+
+	err = ovl_do_set_acl(ofs, dentry, acl_name, clone);
+
+	/* release cloned acl */
+	posix_acl_release(clone);
+	return err;
+}
+
+int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct dentry *new)
+{
+	struct dentry *old = oldpath->dentry;
+	ssize_t list_size, size, value_size = 0;
+	char *buf, *name, *value = NULL;
+	int error = 0;
+	size_t slen;
+
+	if (!old->d_inode->i_op->listxattr || !new->d_inode->i_op->listxattr)
+		return 0;
+
+	list_size = vfs_listxattr(old, NULL, 0);
+	if (list_size <= 0) {
+		if (list_size == -EOPNOTSUPP)
+			return 0;
+		return list_size;
+	}
+
+	buf = kvzalloc(list_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	list_size = vfs_listxattr(old, buf, list_size);
+	if (list_size <= 0) {
+		error = list_size;
+		goto out;
+	}
+
+	for (name = buf; list_size; name += slen) {
+		slen = strnlen(name, list_size) + 1;
+
+		/* underlying fs providing us with an broken xattr list? */
+		if (WARN_ON(slen > list_size)) {
+			error = -EIO;
+			break;
+		}
+		list_size -= slen;
+
+		if (ovl_is_private_xattr(sb, name))
+			continue;
+
+		error = security_inode_copy_up_xattr(old, name);
+		if (error == -ECANCELED) {
+			error = 0;
+			continue; /* Discard */
+		}
+		if (error < 0 && error != -EOPNOTSUPP)
+			break;
+
+		if (is_posix_acl_xattr(name)) {
+			error = ovl_copy_acl(OVL_FS(sb), oldpath, new, name);
+			if (!error)
+				continue;
+			/* POSIX ACLs must be copied. */
+			break;
+		}
+
+retry:
+		size = ovl_do_getxattr(oldpath, name, value, value_size);
+		if (size == -ERANGE)
+			size = ovl_do_getxattr(oldpath, name, NULL, 0);
+
+		if (size < 0) {
+			error = size;
+			break;
+		}
+
+		if (size > value_size) {
+			void *new;
+
+			new = kvmalloc(size, GFP_KERNEL);
+			if (!new) {
+				error = -ENOMEM;
+				break;
+			}
+			kvfree(value);
+			value = new;
+			value_size = size;
+			goto retry;
+		}
+
+		error = ovl_do_setxattr(OVL_FS(sb), new, name, value, size, 0);
+		if (error) {
+			if (error != -EOPNOTSUPP || ovl_must_copy_xattr(name))
+				break;
+
+			/* Ignore failure to copy unknown xattrs */
+			error = 0;
+		}
+	}
+	kvfree(value);
+out:
+	kvfree(buf);
+	return error;
+}
+
+static int ovl_copy_fileattr(struct inode *inode, const struct path *old,
+			     const struct path *new)
+{
+	struct file_kattr oldfa = { .flags_valid = true };
+	struct file_kattr newfa = { .flags_valid = true };
+	int err;
+
+	err = ovl_real_fileattr_get(old, &oldfa);
+	if (err) {
+		/* Ntfs-3g returns -EINVAL for "no fileattr support" */
+		if (err == -ENOTTY || err == -EINVAL)
+			return 0;
+		pr_warn("failed to retrieve lower fileattr (%pd2, err=%i)\n",
+			old->dentry, err);
+		return err;
+	}
+
+	/*
+	 * We cannot set immutable and append-only flags on upper inode,
+	 * because we would not be able to link upper inode to upper dir
+	 * not set overlay private xattr on upper inode.
+	 * Store these flags in overlay.protattr xattr instead.
+	 */
+	if (oldfa.flags & OVL_PROT_FS_FLAGS_MASK) {
+		err = ovl_set_protattr(inode, new->dentry, &oldfa);
+		if (err == -EPERM)
+			pr_warn_once("copying fileattr: no xattr on upper\n");
+		else if (err)
+			return err;
+	}
+
+	/* Don't bother copying flags if none are set */
+	if (!(oldfa.flags & OVL_COPY_FS_FLAGS_MASK))
+		return 0;
+
+	err = ovl_real_fileattr_get(new, &newfa);
+	if (err) {
+		/*
+		 * Returning an error if upper doesn't support fileattr will
+		 * result in a regression, so revert to the old behavior.
+		 */
+		if (err == -ENOTTY || err == -EINVAL) {
+			pr_warn_once("copying fileattr: no support on upper\n");
+			return 0;
+		}
+		pr_warn("failed to retrieve upper fileattr (%pd2, err=%i)\n",
+			new->dentry, err);
+		return err;
+	}
+
+	BUILD_BUG_ON(OVL_COPY_FS_FLAGS_MASK & ~FS_COMMON_FL);
+	newfa.flags &= ~OVL_COPY_FS_FLAGS_MASK;
+	newfa.flags |= (oldfa.flags & OVL_COPY_FS_FLAGS_MASK);
+
+	BUILD_BUG_ON(OVL_COPY_FSX_FLAGS_MASK & ~FS_XFLAG_COMMON);
+	newfa.fsx_xflags &= ~OVL_COPY_FSX_FLAGS_MASK;
+	newfa.fsx_xflags |= (oldfa.fsx_xflags & OVL_COPY_FSX_FLAGS_MASK);
+
+	return ovl_real_fileattr_set(new, &newfa);
+}
+
+static int ovl_verify_area(loff_t pos, loff_t pos2, loff_t len, loff_t totlen)
+{
+	loff_t tmp;
+
+	if (pos != pos2)
+		return -EIO;
+	if (pos < 0 || len < 0 || totlen < 0)
+		return -EIO;
+	if (check_add_overflow(pos, len, &tmp))
+		return -EIO;
+	return 0;
+}
+
+static int ovl_sync_file(const struct path *path)
+{
+	struct file *new_file;
+	int err;
+
+	new_file = ovl_path_open(path, O_LARGEFILE | O_RDONLY);
+	if (IS_ERR(new_file))
+		return PTR_ERR(new_file);
+
+	err = vfs_fsync(new_file, 0);
+	fput(new_file);
+
+	return err;
+}
+
+static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
+			    struct file *new_file, loff_t len,
+			    bool datasync)
+{
+	struct path datapath;
+	struct file *old_file;
+	loff_t old_pos = 0;
+	loff_t new_pos = 0;
+	loff_t cloned;
+	loff_t data_pos = -1;
+	loff_t hole_len;
+	bool skip_hole = false;
+	int error = 0;
+
+	ovl_path_lowerdata(dentry, &datapath);
+	if (WARN_ON_ONCE(datapath.dentry == NULL) ||
+	    WARN_ON_ONCE(len < 0))
+		return -EIO;
+
+	old_file = ovl_path_open(&datapath, O_LARGEFILE | O_RDONLY);
+	if (IS_ERR(old_file))
+		return PTR_ERR(old_file);
+
+	/* Try to use clone_file_range to clone up within the same fs */
+	cloned = vfs_clone_file_range(old_file, 0, new_file, 0, len, 0);
+	if (cloned == len)
+		goto out_fput;
+
+	/* Couldn't clone, so now we try to copy the data */
+	error = rw_verify_area(READ, old_file, &old_pos, len);
+	if (!error)
+		error = rw_verify_area(WRITE, new_file, &new_pos, len);
+	if (error)
+		goto out_fput;
+
+	/* Check if lower fs supports seek operation */
+	if (old_file->f_mode & FMODE_LSEEK)
+		skip_hole = true;
+
+	while (len) {
+		size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
+		ssize_t bytes;
+
+		if (len < this_len)
+			this_len = len;
+
+		if (signal_pending_state(TASK_KILLABLE, current)) {
+			error = -EINTR;
+			break;
+		}
+
+		/*
+		 * Fill zero for hole will cost unnecessary disk space
+		 * and meanwhile slow down the copy-up speed, so we do
+		 * an optimization for hole during copy-up, it relies
+		 * on SEEK_DATA implementation in lower fs so if lower
+		 * fs does not support it, copy-up will behave as before.
+		 *
+		 * Detail logic of hole detection as below:
+		 * When we detect next data position is larger than current
+		 * position we will skip that hole, otherwise we copy
+		 * data in the size of OVL_COPY_UP_CHUNK_SIZE. Actually,
+		 * it may not recognize all kind of holes and sometimes
+		 * only skips partial of hole area. However, it will be
+		 * enough for most of the use cases.
+		 *
+		 * We do not hold upper sb_writers throughout the loop to avert
+		 * lockdep warning with llseek of lower file in nested overlay:
+		 * - upper sb_writers
+		 * -- lower ovl_inode_lock (ovl_llseek)
+		 */
+		if (skip_hole && data_pos < old_pos) {
+			data_pos = vfs_llseek(old_file, old_pos, SEEK_DATA);
+			if (data_pos > old_pos) {
+				hole_len = data_pos - old_pos;
+				len -= hole_len;
+				old_pos = new_pos = data_pos;
+				continue;
+			} else if (data_pos == -ENXIO) {
+				break;
+			} else if (data_pos < 0) {
+				skip_hole = false;
+			}
+		}
+
+		error = ovl_verify_area(old_pos, new_pos, this_len, len);
+		if (error)
+			break;
+
+		bytes = do_splice_direct(old_file, &old_pos,
+					 new_file, &new_pos,
+					 this_len, SPLICE_F_MOVE);
+		if (bytes <= 0) {
+			error = bytes;
+			break;
+		}
+		WARN_ON(old_pos != new_pos);
+
+		len -= bytes;
+	}
+	/* call fsync once, either now or later along with metadata */
+	if (!error && ovl_should_sync(ofs) && datasync)
+		error = vfs_fsync(new_file, 0);
+out_fput:
+	fput(old_file);
+	return error;
+}
+
+static int ovl_set_size(struct ovl_fs *ofs,
+			struct dentry *upperdentry, struct kstat *stat)
+{
+	struct iattr attr = {
+		.ia_valid = ATTR_SIZE,
+		.ia_size = stat->size,
+	};
+
+	return ovl_do_notify_change(ofs, upperdentry, &attr);
+}
+
+static int ovl_set_timestamps(struct ovl_fs *ofs, struct dentry *upperdentry,
+			      struct kstat *stat)
+{
+	struct iattr attr = {
+		.ia_valid =
+		     ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_CTIME,
+		.ia_atime = stat->atime,
+		.ia_mtime = stat->mtime,
+	};
+
+	return ovl_do_notify_change(ofs, upperdentry, &attr);
+}
+
+int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upperdentry,
+		 struct kstat *stat)
+{
+	int err = 0;
+
+	if (!S_ISLNK(stat->mode)) {
+		struct iattr attr = {
+			.ia_valid = ATTR_MODE,
+			.ia_mode = stat->mode,
+		};
+		err = ovl_do_notify_change(ofs, upperdentry, &attr);
+	}
+	if (!err) {
+		struct iattr attr = {
+			.ia_valid = ATTR_UID | ATTR_GID,
+			.ia_vfsuid = VFSUIDT_INIT(stat->uid),
+			.ia_vfsgid = VFSGIDT_INIT(stat->gid),
+		};
+		err = ovl_do_notify_change(ofs, upperdentry, &attr);
+	}
+	if (!err)
+		ovl_set_timestamps(ofs, upperdentry, stat);
+
+	return err;
+}
+
+struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct inode *realinode,
+				  bool is_upper)
+{
+	struct ovl_fh *fh;
+	int fh_type, dwords;
+	int buflen = MAX_HANDLE_SZ;
+	uuid_t *uuid = &realinode->i_sb->s_uuid;
+	int err;
+
+	/* Make sure the real fid stays 32bit aligned */
+	BUILD_BUG_ON(OVL_FH_FID_OFFSET % 4);
+	BUILD_BUG_ON(MAX_HANDLE_SZ + OVL_FH_FID_OFFSET > 255);
+
+	fh = kzalloc(buflen + OVL_FH_FID_OFFSET, GFP_KERNEL);
+	if (!fh)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * We encode a non-connectable file handle for non-dir, because we
+	 * only need to find the lower inode number and we don't want to pay
+	 * the price or reconnecting the dentry.
+	 */
+	dwords = buflen >> 2;
+	fh_type = exportfs_encode_inode_fh(realinode, (void *)fh->fb.fid,
+					   &dwords, NULL, 0);
+	buflen = (dwords << 2);
+
+	err = -EIO;
+	if (fh_type < 0 || fh_type == FILEID_INVALID ||
+	    WARN_ON(buflen > MAX_HANDLE_SZ))
+		goto out_err;
+
+	fh->fb.version = OVL_FH_VERSION;
+	fh->fb.magic = OVL_FH_MAGIC;
+	fh->fb.type = fh_type;
+	fh->fb.flags = OVL_FH_FLAG_CPU_ENDIAN;
+	/*
+	 * When we will want to decode an overlay dentry from this handle
+	 * and all layers are on the same fs, if we get a disconncted real
+	 * dentry when we decode fid, the only way to tell if we should assign
+	 * it to upperdentry or to lowerstack is by checking this flag.
+	 */
+	if (is_upper)
+		fh->fb.flags |= OVL_FH_FLAG_PATH_UPPER;
+	fh->fb.len = sizeof(fh->fb) + buflen;
+	if (ovl_origin_uuid(ofs))
+		fh->fb.uuid = *uuid;
+
+	return fh;
+
+out_err:
+	kfree(fh);
+	return ERR_PTR(err);
+}
+
+struct ovl_fh *ovl_get_origin_fh(struct ovl_fs *ofs, struct dentry *origin)
+{
+	/*
+	 * When lower layer doesn't support export operations store a 'null' fh,
+	 * so we can use the overlay.origin xattr to distignuish between a copy
+	 * up and a pure upper inode.
+	 */
+	if (!ovl_can_decode_fh(origin->d_sb))
+		return NULL;
+
+	return ovl_encode_real_fh(ofs, d_inode(origin), false);
+}
+
+int ovl_set_origin_fh(struct ovl_fs *ofs, const struct ovl_fh *fh,
+		      struct dentry *upper)
+{
+	int err;
+
+	/*
+	 * Do not fail when upper doesn't support xattrs.
+	 */
+	err = ovl_check_setxattr(ofs, upper, OVL_XATTR_ORIGIN, fh->buf,
+				 fh ? fh->fb.len : 0, 0);
+
+	/* Ignore -EPERM from setting "user.*" on symlink/special */
+	return err == -EPERM ? 0 : err;
+}
+
+/* Store file handle of @upper dir in @index dir entry */
+static int ovl_set_upper_fh(struct ovl_fs *ofs, struct dentry *upper,
+			    struct dentry *index)
+{
+	const struct ovl_fh *fh;
+	int err;
+
+	fh = ovl_encode_real_fh(ofs, d_inode(upper), true);
+	if (IS_ERR(fh))
+		return PTR_ERR(fh);
+
+	err = ovl_setxattr(ofs, index, OVL_XATTR_UPPER, fh->buf, fh->fb.len);
+
+	kfree(fh);
+	return err;
+}
+
+/*
+ * Create and install index entry.
+ */
+static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh,
+			    struct dentry *upper)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
+	struct dentry *temp = NULL;
+	struct renamedata rd = {};
+	struct qstr name = { };
+	int err;
+
+	/*
+	 * For now this is only used for creating index entry for directories,
+	 * because non-dir are copied up directly to index and then hardlinked
+	 * to upper dir.
+	 *
+	 * TODO: implement create index for non-dir, so we can call it when
+	 * encoding file handle for non-dir in case index does not exist.
+	 */
+	if (WARN_ON(!d_is_dir(dentry)))
+		return -EIO;
+
+	/* Directory not expected to be indexed before copy up */
+	if (WARN_ON(ovl_test_flag(OVL_INDEX, d_inode(dentry))))
+		return -EIO;
+
+	err = ovl_get_index_name_fh(fh, &name);
+	if (err)
+		return err;
+
+	temp = ovl_create_temp(ofs, indexdir, OVL_CATTR(S_IFDIR | 0));
+	err = PTR_ERR(temp);
+	if (IS_ERR(temp))
+		goto free_name;
+
+	err = ovl_set_upper_fh(ofs, upper, temp);
+	if (err)
+		goto out;
+
+	rd.mnt_idmap = ovl_upper_mnt_idmap(ofs);
+	rd.old_parent = indexdir;
+	rd.new_parent = indexdir;
+	err = start_renaming_dentry(&rd, 0, temp, &name);
+	if (err)
+		goto out;
+
+	err = ovl_do_rename_rd(&rd);
+	end_renaming(&rd);
+out:
+	if (err)
+		ovl_cleanup(ofs, indexdir, temp);
+	dput(temp);
+free_name:
+	kfree(name.name);
+	return err;
+}
+
+struct ovl_copy_up_ctx {
+	struct dentry *parent;
+	struct dentry *dentry;
+	struct path lowerpath;
+	struct kstat stat;
+	struct kstat pstat;
+	const char *link;
+	struct dentry *destdir;
+	struct qstr destname;
+	struct dentry *workdir;
+	const struct ovl_fh *origin_fh;
+	bool origin;
+	bool indexed;
+	bool metacopy;
+	bool metacopy_digest;
+	bool metadata_fsync;
+};
+
+static int ovl_link_up(struct ovl_copy_up_ctx *c)
+{
+	int err;
+	struct dentry *upper;
+	struct dentry *upperdir = ovl_dentry_upper(c->parent);
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct inode *udir = d_inode(upperdir);
+
+	ovl_start_write(c->dentry);
+
+	/* Mark parent "impure" because it may now contain non-pure upper */
+	err = ovl_set_impure(c->parent, upperdir);
+	if (err)
+		goto out;
+
+	err = ovl_set_nlink_lower(c->dentry);
+	if (err)
+		goto out;
+
+	upper = ovl_start_creating_upper(ofs, upperdir,
+					 &QSTR_LEN(c->dentry->d_name.name,
+						   c->dentry->d_name.len));
+	err = PTR_ERR(upper);
+	if (!IS_ERR(upper)) {
+		err = ovl_do_link(ofs, ovl_dentry_upper(c->dentry), udir, upper);
+
+		if (!err) {
+			/* Restore timestamps on parent (best effort) */
+			ovl_set_timestamps(ofs, upperdir, &c->pstat);
+			ovl_dentry_set_upper_alias(c->dentry);
+			ovl_dentry_update_reval(c->dentry, upper);
+		}
+		end_creating(upper);
+	}
+	if (err)
+		goto out;
+
+	err = ovl_set_nlink_upper(c->dentry);
+
+out:
+	ovl_end_write(c->dentry);
+	return err;
+}
+
+static int ovl_copy_up_data(struct ovl_copy_up_ctx *c, const struct path *temp)
+{
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct file *new_file;
+	int err;
+
+	if (!S_ISREG(c->stat.mode) || c->metacopy || !c->stat.size)
+		return 0;
+
+	new_file = ovl_path_open(temp, O_LARGEFILE | O_WRONLY);
+	if (IS_ERR(new_file))
+		return PTR_ERR(new_file);
+
+	err = ovl_copy_up_file(ofs, c->dentry, new_file, c->stat.size,
+			       !c->metadata_fsync);
+	fput(new_file);
+
+	return err;
+}
+
+static int ovl_copy_up_metadata(struct ovl_copy_up_ctx *c, struct dentry *temp)
+{
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct inode *inode = d_inode(c->dentry);
+	struct path upperpath = { .mnt = ovl_upper_mnt(ofs), .dentry = temp };
+	int err;
+
+	err = ovl_copy_xattr(c->dentry->d_sb, &c->lowerpath, temp);
+	if (err)
+		return err;
+
+	if (inode->i_flags & OVL_FATTR_I_FLAGS_MASK &&
+	    (S_ISREG(c->stat.mode) || S_ISDIR(c->stat.mode))) {
+		/*
+		 * Copy the fileattr inode flags that are the source of already
+		 * copied i_flags
+		 */
+		err = ovl_copy_fileattr(inode, &c->lowerpath, &upperpath);
+		if (err)
+			return err;
+	}
+
+	/*
+	 * Store identifier of lower inode in upper inode xattr to
+	 * allow lookup of the copy up origin inode.
+	 *
+	 * Don't set origin when we are breaking the association with a lower
+	 * hard link.
+	 */
+	if (c->origin) {
+		err = ovl_set_origin_fh(ofs, c->origin_fh, temp);
+		if (err)
+			return err;
+	}
+
+	if (c->metacopy) {
+		struct path lowerdatapath;
+		struct ovl_metacopy metacopy_data = OVL_METACOPY_INIT;
+
+		ovl_path_lowerdata(c->dentry, &lowerdatapath);
+		if (WARN_ON_ONCE(lowerdatapath.dentry == NULL))
+			return -EIO;
+		err = ovl_get_verity_digest(ofs, &lowerdatapath, &metacopy_data);
+		if (err)
+			return err;
+
+		if (metacopy_data.digest_algo)
+			c->metacopy_digest = true;
+
+		err = ovl_set_metacopy_xattr(ofs, temp, &metacopy_data);
+		if (err)
+			return err;
+	}
+
+	inode_lock(temp->d_inode);
+	if (S_ISREG(c->stat.mode))
+		err = ovl_set_size(ofs, temp, &c->stat);
+	if (!err)
+		err = ovl_set_attr(ofs, temp, &c->stat);
+	inode_unlock(temp->d_inode);
+
+	/* fsync metadata before moving it into upper dir */
+	if (!err && ovl_should_sync(ofs) && c->metadata_fsync)
+		err = ovl_sync_file(&upperpath);
+
+	return err;
+}
+
+static const struct cred *ovl_prepare_copy_up_creds(struct dentry *dentry)
+{
+	struct cred *copy_up_cred = NULL;
+	int err;
+
+	err = security_inode_copy_up(dentry, &copy_up_cred);
+	if (err < 0)
+		return ERR_PTR(err);
+
+	if (!copy_up_cred)
+		return NULL;
+
+	return override_creds(copy_up_cred);
+}
+
+static void ovl_revert_copy_up_creds(const struct cred *orig_cred)
+{
+	const struct cred *copy_up_cred;
+
+	copy_up_cred = revert_creds(orig_cred);
+	put_cred(copy_up_cred);
+}
+
+DEFINE_CLASS(copy_up_creds, const struct cred *,
+	     if (!IS_ERR_OR_NULL(_T)) ovl_revert_copy_up_creds(_T),
+	     ovl_prepare_copy_up_creds(dentry), struct dentry *dentry)
+
+/*
+ * Copyup using workdir to prepare temp file.  Used when copying up directories,
+ * special files or when upper fs doesn't support O_TMPFILE.
+ */
+static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
+{
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct inode *inode;
+	struct path path = { .mnt = ovl_upper_mnt(ofs) };
+	struct renamedata rd = {};
+	struct dentry *temp;
+	int err;
+	struct ovl_cattr cattr = {
+		/* Can't properly set mode on creation because of the umask */
+		.mode = c->stat.mode & S_IFMT,
+		.rdev = c->stat.rdev,
+		.link = c->link
+	};
+
+	scoped_class(copy_up_creds, copy_up_creds, c->dentry) {
+		if (IS_ERR(copy_up_creds))
+			return PTR_ERR(copy_up_creds);
+
+		ovl_start_write(c->dentry);
+		temp = ovl_create_temp(ofs, c->workdir, &cattr);
+		ovl_end_write(c->dentry);
+	}
+
+	if (IS_ERR(temp))
+		return PTR_ERR(temp);
+
+	/*
+	 * Copy up data first and then xattrs. Writing data after
+	 * xattrs will remove security.capability xattr automatically.
+	 */
+	path.dentry = temp;
+	err = ovl_copy_up_data(c, &path);
+	ovl_start_write(c->dentry);
+	if (err)
+		goto cleanup_unlocked;
+
+	if (S_ISDIR(c->stat.mode) && c->indexed) {
+		err = ovl_create_index(c->dentry, c->origin_fh, temp);
+		if (err)
+			goto cleanup_unlocked;
+	}
+
+	/*
+	 * We cannot hold lock_rename() throughout this helper, because of
+	 * lock ordering with sb_writers, which shouldn't be held when calling
+	 * ovl_copy_up_data(), so lock workdir and destdir and make sure that
+	 * temp wasn't moved before copy up completion or cleanup.
+	 */
+	rd.mnt_idmap = ovl_upper_mnt_idmap(ofs);
+	rd.old_parent = c->workdir;
+	rd.new_parent = c->destdir;
+	rd.flags = 0;
+	err = start_renaming_dentry(&rd, 0, temp,
+				    &QSTR_LEN(c->destname.name, c->destname.len));
+	if (err) {
+		/* temp or workdir moved underneath us? map to -EIO */
+		err = -EIO;
+	}
+	if (err)
+		goto cleanup_unlocked;
+
+	err = ovl_copy_up_metadata(c, temp);
+	if (!err)
+		err = ovl_do_rename_rd(&rd);
+	end_renaming(&rd);
+
+	if (err)
+		goto cleanup_unlocked;
+
+	inode = d_inode(c->dentry);
+	if (c->metacopy_digest)
+		ovl_set_flag(OVL_HAS_DIGEST, inode);
+	else
+		ovl_clear_flag(OVL_HAS_DIGEST, inode);
+	ovl_clear_flag(OVL_VERIFIED_DIGEST, inode);
+
+	if (!c->metacopy)
+		ovl_set_upperdata(inode);
+	ovl_inode_update(inode, temp);
+	if (S_ISDIR(inode->i_mode))
+		ovl_set_flag(OVL_WHITEOUTS, inode);
+out:
+	ovl_end_write(c->dentry);
+
+	return err;
+
+cleanup_unlocked:
+	ovl_cleanup(ofs, c->workdir, temp);
+	dput(temp);
+	goto out;
+}
+
+/* Copyup using O_TMPFILE which does not require cross dir locking */
+static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)
+{
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct inode *udir = d_inode(c->destdir);
+	struct dentry *temp, *upper, *newdentry = NULL;
+	struct file *tmpfile;
+	int err;
+
+	scoped_class(copy_up_creds, copy_up_creds, c->dentry) {
+		if (IS_ERR(copy_up_creds))
+			return PTR_ERR(copy_up_creds);
+
+		ovl_start_write(c->dentry);
+		tmpfile = ovl_do_tmpfile(ofs, c->workdir, c->stat.mode);
+		ovl_end_write(c->dentry);
+	}
+
+	if (IS_ERR(tmpfile))
+		return PTR_ERR(tmpfile);
+
+	temp = tmpfile->f_path.dentry;
+	if (!c->metacopy && c->stat.size) {
+		err = ovl_copy_up_file(ofs, c->dentry, tmpfile, c->stat.size,
+				       !c->metadata_fsync);
+		if (err)
+			goto out_fput;
+	}
+
+	ovl_start_write(c->dentry);
+
+	err = ovl_copy_up_metadata(c, temp);
+	if (err)
+		goto out;
+
+	upper = ovl_start_creating_upper(ofs, c->destdir,
+					 &QSTR_LEN(c->destname.name,
+						   c->destname.len));
+	err = PTR_ERR(upper);
+	if (!IS_ERR(upper)) {
+		err = ovl_do_link(ofs, temp, udir, upper);
+		if (!err) {
+			/*
+			 * Record the linked dentry -- not the disconnected
+			 * O_TMPFILE dentry -- so that ->d_revalidate() on
+			 * the upper fs sees the real parent/name.
+			 */
+			newdentry = dget(upper);
+		}
+		end_creating(upper);
+	}
+
+	if (err)
+		goto out;
+
+	if (c->metacopy_digest)
+		ovl_set_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
+	else
+		ovl_clear_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
+	ovl_clear_flag(OVL_VERIFIED_DIGEST, d_inode(c->dentry));
+
+	if (!c->metacopy)
+		ovl_set_upperdata(d_inode(c->dentry));
+	ovl_inode_update(d_inode(c->dentry), newdentry);
+
+out:
+	ovl_end_write(c->dentry);
+out_fput:
+	fput(tmpfile);
+	return err;
+}
+
+/*
+ * Copy up a single dentry
+ *
+ * All renames start with copy up of source if necessary.  The actual
+ * rename will only proceed once the copy up was successful.  Copy up uses
+ * upper parent i_mutex for exclusion.  Since rename can change d_parent it
+ * is possible that the copy up will lock the old parent.  At that point
+ * the file will have already been copied up anyway.
+ */
+static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
+{
+	int err;
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct dentry *origin = c->lowerpath.dentry;
+	struct ovl_fh *fh = NULL;
+	bool to_index = false;
+
+	/*
+	 * Indexed non-dir is copied up directly to the index entry and then
+	 * hardlinked to upper dir. Indexed dir is copied up to indexdir,
+	 * then index entry is created and then copied up dir installed.
+	 * Copying dir up to indexdir instead of workdir simplifies locking.
+	 */
+	if (ovl_need_index(c->dentry)) {
+		c->indexed = true;
+		if (S_ISDIR(c->stat.mode))
+			c->workdir = ovl_indexdir(c->dentry->d_sb);
+		else
+			to_index = true;
+	}
+
+	if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || to_index) {
+		fh = ovl_get_origin_fh(ofs, origin);
+		if (IS_ERR(fh))
+			return PTR_ERR(fh);
+
+		/* origin_fh may be NULL */
+		c->origin_fh = fh;
+		c->origin = true;
+	}
+
+	if (to_index) {
+		c->destdir = ovl_indexdir(c->dentry->d_sb);
+		err = ovl_get_index_name(ofs, origin, &c->destname);
+		if (err)
+			goto out_free_fh;
+	} else if (WARN_ON(!c->parent)) {
+		/* Disconnected dentry must be copied up to index dir */
+		err = -EIO;
+		goto out_free_fh;
+	} else {
+		/*
+		 * c->dentry->d_name is stabilzed by ovl_copy_up_start(),
+		 * because if we got here, it means that c->dentry has no upper
+		 * alias and changing ->d_name means going through ovl_rename()
+		 * that will call ovl_copy_up() on source and target dentry.
+		 */
+		c->destname = c->dentry->d_name;
+		/*
+		 * Mark parent "impure" because it may now contain non-pure
+		 * upper
+		 */
+		ovl_start_write(c->dentry);
+		err = ovl_set_impure(c->parent, c->destdir);
+		ovl_end_write(c->dentry);
+		if (err)
+			goto out_free_fh;
+	}
+
+	/* Should we copyup with O_TMPFILE or with workdir? */
+	if (S_ISREG(c->stat.mode) && ofs->tmpfile)
+		err = ovl_copy_up_tmpfile(c);
+	else
+		err = ovl_copy_up_workdir(c);
+	if (err)
+		goto out;
+
+	if (c->indexed)
+		ovl_set_flag(OVL_INDEX, d_inode(c->dentry));
+
+	ovl_start_write(c->dentry);
+	if (to_index) {
+		/* Initialize nlink for copy up of disconnected dentry */
+		err = ovl_set_nlink_upper(c->dentry);
+	} else {
+		struct inode *udir = d_inode(c->destdir);
+
+		/* Restore timestamps on parent (best effort) */
+		inode_lock(udir);
+		ovl_set_timestamps(ofs, c->destdir, &c->pstat);
+		inode_unlock(udir);
+
+		ovl_dentry_set_upper_alias(c->dentry);
+		ovl_dentry_update_reval(c->dentry, ovl_dentry_upper(c->dentry));
+	}
+	ovl_end_write(c->dentry);
+
+out:
+	if (to_index)
+		kfree(c->destname.name);
+out_free_fh:
+	kfree(fh);
+	return err;
+}
+
+static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
+				  int flags)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+
+	if (!ofs->config.metacopy)
+		return false;
+
+	if (!S_ISREG(mode))
+		return false;
+
+	if (flags && ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC)))
+		return false;
+
+	/* Fall back to full copy if no fsverity on source data and we require verity */
+	if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
+		struct path lowerdata;
+
+		ovl_path_lowerdata(dentry, &lowerdata);
+
+		if (WARN_ON_ONCE(lowerdata.dentry == NULL) ||
+		    ovl_ensure_verity_loaded(&lowerdata) ||
+		    !fsverity_active(d_inode(lowerdata.dentry))) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static ssize_t ovl_getxattr_value(const struct path *path, char *name, char **value)
+{
+	ssize_t res;
+	char *buf;
+
+	res = ovl_do_getxattr(path, name, NULL, 0);
+	if (res == -ENODATA || res == -EOPNOTSUPP)
+		res = 0;
+
+	if (res > 0) {
+		buf = kzalloc(res, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+
+		res = ovl_do_getxattr(path, name, buf, res);
+		if (res < 0)
+			kfree(buf);
+		else
+			*value = buf;
+	}
+	return res;
+}
+
+/* Copy up data of an inode which was copied up metadata only in the past. */
+static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
+{
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
+	struct path upperpath;
+	int err;
+	char *capability = NULL;
+	ssize_t cap_size;
+
+	ovl_path_upper(c->dentry, &upperpath);
+	if (WARN_ON(upperpath.dentry == NULL))
+		return -EIO;
+
+	if (c->stat.size) {
+		err = cap_size = ovl_getxattr_value(&upperpath, XATTR_NAME_CAPS,
+						    &capability);
+		if (cap_size < 0)
+			goto out;
+	}
+
+	err = ovl_copy_up_data(c, &upperpath);
+	if (err)
+		goto out_free;
+
+	/*
+	 * Writing to upper file will clear security.capability xattr. We
+	 * don't want that to happen for normal copy-up operation.
+	 */
+	ovl_start_write(c->dentry);
+	if (capability) {
+		err = ovl_do_setxattr(ofs, upperpath.dentry, XATTR_NAME_CAPS,
+				      capability, cap_size, 0);
+	}
+	if (!err) {
+		err = ovl_removexattr(ofs, upperpath.dentry,
+				      OVL_XATTR_METACOPY);
+	}
+	ovl_end_write(c->dentry);
+	if (err)
+		goto out_free;
+
+	ovl_clear_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
+	ovl_clear_flag(OVL_VERIFIED_DIGEST, d_inode(c->dentry));
+	ovl_set_upperdata(d_inode(c->dentry));
+out_free:
+	kfree(capability);
+out:
+	return err;
+}
+
+static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
+			   int flags)
+{
+	int err;
+	DEFINE_DELAYED_CALL(done);
+	struct path parentpath;
+	struct ovl_copy_up_ctx ctx = {
+		.parent = parent,
+		.dentry = dentry,
+		.workdir = ovl_workdir(dentry),
+	};
+
+	if (WARN_ON(!ctx.workdir))
+		return -EROFS;
+
+	ovl_path_lower(dentry, &ctx.lowerpath);
+	err = vfs_getattr(&ctx.lowerpath, &ctx.stat,
+			  STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
+	if (err)
+		return err;
+
+	if (!kuid_has_mapping(current_user_ns(), ctx.stat.uid) ||
+	    !kgid_has_mapping(current_user_ns(), ctx.stat.gid))
+		return -EOVERFLOW;
+
+	/*
+	 * With "fsync=strict", we fsync after final metadata copyup, for
+	 * both regular files and directories to get atomic copyup semantics
+	 * on filesystems that do not use strict metadata ordering (e.g. ubifs).
+	 *
+	 * By default, we want to avoid fsync on all meta copyup, because
+	 * that will hurt performance of workloads such as chown -R, so we
+	 * only fsync on data copyup as legacy behavior.
+	 */
+	ctx.metadata_fsync = ovl_should_sync_metadata(OVL_FS(dentry->d_sb)) &&
+			     (S_ISREG(ctx.stat.mode) || S_ISDIR(ctx.stat.mode));
+	ctx.metacopy = ovl_need_meta_copy_up(dentry, ctx.stat.mode, flags);
+
+	if (parent) {
+		ovl_path_upper(parent, &parentpath);
+		ctx.destdir = parentpath.dentry;
+
+		err = vfs_getattr(&parentpath, &ctx.pstat,
+				  STATX_ATIME | STATX_MTIME,
+				  AT_STATX_SYNC_AS_STAT);
+		if (err)
+			return err;
+	}
+
+	/* maybe truncate regular file. this has no effect on dirs */
+	if (flags & O_TRUNC)
+		ctx.stat.size = 0;
+
+	if (S_ISLNK(ctx.stat.mode)) {
+		ctx.link = vfs_get_link(ctx.lowerpath.dentry, &done);
+		if (IS_ERR(ctx.link))
+			return PTR_ERR(ctx.link);
+	}
+
+	err = ovl_copy_up_start(dentry, flags);
+	/* err < 0: interrupted, err > 0: raced with another copy-up */
+	if (unlikely(err)) {
+		if (err > 0)
+			err = 0;
+	} else {
+		if (!ovl_dentry_upper(dentry))
+			err = ovl_do_copy_up(&ctx);
+		if (!err && parent && !ovl_dentry_has_upper_alias(dentry))
+			err = ovl_link_up(&ctx);
+		if (!err && ovl_dentry_needs_data_copy_up_locked(dentry, flags))
+			err = ovl_copy_up_meta_inode_data(&ctx);
+		ovl_copy_up_end(dentry);
+	}
+	do_delayed_call(&done);
+
+	return err;
+}
+
+static int ovl_copy_up_flags(struct dentry *dentry, int flags)
+{
+	int err = 0;
+	bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);
+
+	/*
+	 * With NFS export, copy up can get called for a disconnected non-dir.
+	 * In this case, we will copy up lower inode to index dir without
+	 * linking it to upper dir.
+	 */
+	if (WARN_ON(disconnected && d_is_dir(dentry)))
+		return -EIO;
+
+	/*
+	 * We may not need lowerdata if we are only doing metacopy up, but it is
+	 * not very important to optimize this case, so do lazy lowerdata lookup
+	 * before any copy up, so we can do it before taking ovl_inode_lock().
+	 */
+	err = ovl_verify_lowerdata(dentry);
+	if (err)
+		return err;
+
+	while (!err) {
+		struct dentry *next;
+		struct dentry *parent = NULL;
+
+		if (ovl_already_copied_up(dentry, flags))
+			break;
+
+		next = dget(dentry);
+		/* find the topmost dentry not yet copied up */
+		for (; !disconnected;) {
+			parent = dget_parent(next);
+
+			if (ovl_dentry_upper(parent))
+				break;
+
+			dput(next);
+			next = parent;
+		}
+
+		with_ovl_creds(dentry->d_sb)
+			err = ovl_copy_up_one(parent, next, flags);
+
+		dput(parent);
+		dput(next);
+	}
+
+	return err;
+}
+
+static bool ovl_open_need_copy_up(struct dentry *dentry, int flags)
+{
+	/* Copy up of disconnected dentry does not set upper alias */
+	if (ovl_already_copied_up(dentry, flags))
+		return false;
+
+	if (special_file(d_inode(dentry)->i_mode))
+		return false;
+
+	if (!ovl_open_flags_need_copy_up(flags))
+		return false;
+
+	return true;
+}
+
+int ovl_maybe_copy_up(struct dentry *dentry, int flags)
+{
+	if (!ovl_open_need_copy_up(dentry, flags))
+		return 0;
+
+	return ovl_copy_up_flags(dentry, flags);
+}
+
+int ovl_copy_up_with_data(struct dentry *dentry)
+{
+	return ovl_copy_up_flags(dentry, O_WRONLY);
+}
+
+int ovl_copy_up(struct dentry *dentry)
+{
+	return ovl_copy_up_flags(dentry, 0);
+}