[Feature] add GA346 baseline version
Change-Id: Ic62933698569507dcf98240cdf5d9931ae34348f
diff --git a/src/kernel/linux/v4.19/fs/overlayfs/namei.c b/src/kernel/linux/v4.19/fs/overlayfs/namei.c
new file mode 100644
index 0000000..499cd1f
--- /dev/null
+++ b/src/kernel/linux/v4.19/fs/overlayfs/namei.c
@@ -0,0 +1,1166 @@
+/*
+ * Copyright (C) 2011 Novell Inc.
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/cred.h>
+#include <linux/ctype.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/ratelimit.h>
+#include <linux/mount.h>
+#include <linux/exportfs.h>
+#include "overlayfs.h"
+
+struct ovl_lookup_data {
+ struct super_block *sb;
+ struct qstr name;
+ bool is_dir;
+ bool opaque;
+ bool stop;
+ bool last;
+ char *redirect;
+ bool metacopy;
+};
+
+static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
+ size_t prelen, const char *post)
+{
+ int res;
+ char *buf;
+
+ buf = ovl_get_redirect_xattr(dentry, prelen + strlen(post));
+ if (IS_ERR_OR_NULL(buf))
+ return PTR_ERR(buf);
+
+ if (buf[0] == '/') {
+ /*
+ * One of the ancestor path elements in an absolute path
+ * lookup in ovl_lookup_layer() could have been opaque and
+ * that will stop further lookup in lower layers (d->stop=true)
+ * But we have found an absolute redirect in decendant path
+ * element and that should force continue lookup in lower
+ * layers (reset d->stop).
+ */
+ d->stop = false;
+ } else {
+ res = strlen(buf) + 1;
+ memmove(buf + prelen, buf, res);
+ memcpy(buf, d->name.name, prelen);
+ }
+
+ strcat(buf, post);
+ kfree(d->redirect);
+ d->redirect = buf;
+ d->name.name = d->redirect;
+ d->name.len = strlen(d->redirect);
+
+ return 0;
+}
+
+static int ovl_acceptable(void *ctx, struct dentry *dentry)
+{
+ /*
+ * 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);
+}
+
+/*
+ * 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)
+{
+ 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)
+{
+ ssize_t res;
+ int err;
+ struct ovl_fh *fh = NULL;
+
+ res = ovl_vfs_getxattr(dentry, name, NULL, 0);
+ if (res < 0) {
+ if (res == -ENODATA || res == -EOPNOTSUPP)
+ return NULL;
+ goto fail;
+ }
+ /* Zero size value means "copied up but origin unknown" */
+ if (res == 0)
+ return NULL;
+
+ fh = kzalloc(res, GFP_KERNEL);
+ if (!fh)
+ return ERR_PTR(-ENOMEM);
+
+ res = ovl_vfs_getxattr(dentry, name, fh, res);
+ if (res < 0)
+ goto fail;
+
+ err = ovl_check_fh_len(fh, res);
+ if (err < 0) {
+ if (err == -ENODATA)
+ goto out;
+ goto invalid;
+ }
+
+ return fh;
+
+out:
+ kfree(fh);
+ return NULL;
+
+fail:
+ pr_warn_ratelimited("overlayfs: failed to get origin (%zi)\n", res);
+ goto out;
+invalid:
+ pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n",
+ (int)res, fh);
+ goto out;
+}
+
+struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
+ bool connected)
+{
+ struct dentry *real;
+ int bytes;
+
+ /*
+ * 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))
+ return NULL;
+
+ bytes = (fh->len - offsetof(struct ovl_fh, fid));
+ real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
+ bytes >> 2, (int)fh->type,
+ connected ? ovl_acceptable : NULL, 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(real)) {
+ dput(real);
+ return NULL;
+ }
+
+ return real;
+}
+
+static bool ovl_is_opaquedir(struct dentry *dentry)
+{
+ return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE);
+}
+
+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 *this;
+ int err;
+ bool last_element = !post[0];
+
+ this = lookup_one_len_unlocked(name, base, namelen);
+ if (IS_ERR(this)) {
+ err = PTR_ERR(this);
+ this = NULL;
+ if (err == -ENOENT || err == -ENAMETOOLONG)
+ goto out;
+ goto out_err;
+ }
+ if (!this->d_inode)
+ goto put_and_out;
+
+ if (ovl_dentry_weird(this)) {
+ /* Don't support traversing automounts and other weirdness */
+ err = -EREMOTE;
+ goto out_err;
+ }
+ if (ovl_is_whiteout(this)) {
+ d->stop = d->opaque = true;
+ goto put_and_out;
+ }
+ /*
+ * This dentry should be a regular file if previous layer lookup
+ * found a metacopy dentry.
+ */
+ if (last_element && d->metacopy && !d_is_reg(this)) {
+ d->stop = true;
+ goto put_and_out;
+ }
+ if (!d_can_lookup(this)) {
+ if (d->is_dir || !last_element) {
+ d->stop = true;
+ goto put_and_out;
+ }
+ err = ovl_check_metacopy_xattr(this);
+ if (err < 0)
+ goto out_err;
+
+ d->metacopy = err;
+ d->stop = !d->metacopy;
+ if (!d->metacopy || d->last)
+ goto out;
+ } else {
+ if (ovl_lookup_trap_inode(d->sb, this)) {
+ /* Caught in a trap of overlapping layers */
+ err = -ELOOP;
+ goto out_err;
+ }
+
+ if (last_element)
+ d->is_dir = true;
+ if (d->last)
+ goto out;
+
+ if (ovl_is_opaquedir(this)) {
+ d->stop = true;
+ if (last_element)
+ d->opaque = true;
+ goto out;
+ }
+ }
+ err = ovl_check_redirect(this, d, prelen, post);
+ if (err)
+ goto out_err;
+out:
+ *ret = this;
+ return 0;
+
+put_and_out:
+ dput(this);
+ this = NULL;
+ goto out;
+
+out_err:
+ dput(this);
+ return err;
+}
+
+static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
+ struct dentry **ret)
+{
+ /* Counting down from the end, since the prefix can change */
+ size_t rem = d->name.len - 1;
+ struct dentry *dentry = NULL;
+ int err;
+
+ if (d->name.name[0] != '/')
+ return ovl_lookup_single(base, d, d->name.name, d->name.len,
+ 0, "", ret);
+
+ while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
+ const char *s = d->name.name + d->name.len - rem;
+ const char *next = strchrnul(s, '/');
+ size_t thislen = next - s;
+ bool end = !next[0];
+
+ /* Verify we did not go off the rails */
+ if (WARN_ON(s[-1] != '/'))
+ return -EIO;
+
+ err = ovl_lookup_single(base, d, s, thislen,
+ d->name.len - rem, next, &base);
+ dput(dentry);
+ if (err)
+ return err;
+ dentry = base;
+ if (end)
+ break;
+
+ rem -= thislen + 1;
+
+ if (WARN_ON(rem >= d->name.len))
+ return -EIO;
+ }
+ *ret = dentry;
+ return 0;
+}
+
+
+int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
+ struct dentry *upperdentry, struct ovl_path **stackp)
+{
+ struct dentry *origin = NULL;
+ int i;
+
+ for (i = 0; i < ofs->numlower; i++) {
+ origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt,
+ connected);
+ if (origin)
+ break;
+ }
+
+ if (!origin)
+ 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;
+
+ if (!*stackp)
+ *stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL);
+ if (!*stackp) {
+ dput(origin);
+ return -ENOMEM;
+ }
+ **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, false, 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 file handle stored in xattr @name.
+ * Return 0 on match, -ESTALE on mismatch, < 0 on error.
+ */
+static int ovl_verify_fh(struct dentry *dentry, const char *name,
+ const struct ovl_fh *fh)
+{
+ struct ovl_fh *ofh = ovl_get_fh(dentry, name);
+ int err = 0;
+
+ if (!ofh)
+ return -ENODATA;
+
+ if (IS_ERR(ofh))
+ return PTR_ERR(ofh);
+
+ if (fh->len != ofh->len || memcmp(fh, ofh, fh->len))
+ err = -ESTALE;
+
+ kfree(ofh);
+ return err;
+}
+
+/*
+ * Verify that @real dentry matches the file handle stored in xattr @name.
+ *
+ * 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, -ENODATA on no xattr, < 0 on error.
+ */
+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_real_fh(real, is_upper);
+ err = PTR_ERR(fh);
+ if (IS_ERR(fh)) {
+ fh = NULL;
+ goto fail;
+ }
+
+ err = ovl_verify_fh(dentry, name, fh);
+ if (set && err == -ENODATA)
+ err = ovl_do_setxattr(dentry, name, fh, fh->len, 0);
+ if (err)
+ goto fail;
+
+out:
+ kfree(fh);
+ return err;
+
+fail:
+ 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_real_fh(fh, ofs->upper_mnt, true);
+ 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 ovl_fs *ofs, struct dentry *index)
+{
+ struct ovl_fh *fh = NULL;
+ size_t len;
+ struct ovl_path origin = { };
+ struct ovl_path *stack = &origin;
+ struct dentry *upper = NULL;
+ int err;
+
+ 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_fh)*2)
+ goto fail;
+
+ err = -ENOMEM;
+ len = index->d_name.len / 2;
+ fh = kzalloc(len, GFP_KERNEL);
+ if (!fh)
+ goto fail;
+
+ err = -EINVAL;
+ if (hex2bin((u8 *)fh, index->d_name.name, len))
+ goto fail;
+
+ err = ovl_check_fh_len(fh, len);
+ if (err)
+ goto fail;
+
+ /*
+ * 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 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, false, index, &stack);
+ if (err)
+ goto fail;
+
+ if (ovl_get_nlink(origin.dentry, index, 0) == 0)
+ goto orphan;
+ }
+
+out:
+ dput(origin.dentry);
+ kfree(fh);
+ return err;
+
+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 = kcalloc(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;
+
+}
+
+/*
+ * Lookup in indexdir for the index entry of a lower real inode or a copy up
+ * origin inode. The index entry name is the hex representation of the lower
+ * inode file handle.
+ *
+ * If the index dentry in negative, then either no lower aliases have been
+ * copied up yet, or aliases have been copied up in older kernels and are
+ * not indexed.
+ *
+ * If the index dentry for a copy up origin inode is positive, but points
+ * to an inode different than the upper inode, then either the upper inode
+ * has been copied up and not indexed or it was indexed, but since then
+ * index dir was cleared. Either way, that index cannot be used to indentify
+ * the overlay inode.
+ */
+int ovl_get_index_name(struct dentry *origin, struct qstr *name)
+{
+ struct ovl_fh *fh;
+ int err;
+
+ fh = ovl_encode_real_fh(origin, false);
+ if (IS_ERR(fh))
+ return PTR_ERR(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);
+}
+
+struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
+ struct dentry *origin, bool verify)
+{
+ 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);
+ if (err)
+ return ERR_PTR(err);
+
+ index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
+ if (IS_ERR(index)) {
+ err = PTR_ERR(index);
+ if (err == -ENOENT) {
+ index = NULL;
+ goto out;
+ }
+ pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%.*s, err=%i);\n"
+ "overlayfs: mount with '-o index=off' to disable inodes index.\n",
+ d_inode(origin)->i_ino, name.len, name.name,
+ err);
+ goto out;
+ }
+
+ inode = d_inode(index);
+ if (d_is_negative(index)) {
+ 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)) {
+ /*
+ * Index should always be of the same file type as origin
+ * except for the case of a whiteout index. A whiteout
+ * index should only exist if all lower aliases have been
+ * unlinked, which means that finding a lower origin on lookup
+ * whose index is a whiteout should be treated as an error.
+ */
+ pr_warn_ratelimited("overlayfs: bad index found (index=%pd2, ftype=%x, origin ftype=%x).\n",
+ 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;
+
+out_dput:
+ dput(index);
+ index = NULL;
+ goto out;
+
+fail:
+ dput(index);
+ index = ERR_PTR(-EIO);
+ goto out;
+}
+
+/*
+ * Returns next layer in stack starting from top.
+ * Returns -1 if this is the last layer.
+ */
+int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ BUG_ON(idx < 0);
+ if (idx == 0) {
+ ovl_path_upper(dentry, path);
+ if (path->dentry)
+ return oe->numlower ? 1 : -1;
+ idx++;
+ }
+ BUG_ON(idx > oe->numlower);
+ path->dentry = oe->lowerstack[idx - 1].dentry;
+ path->mnt = oe->lowerstack[idx - 1].layer->mnt;
+
+ return (idx < oe->numlower) ? idx + 1 : -1;
+}
+
+/* Fix missing 'origin' xattr */
+static int ovl_fix_origin(struct dentry *dentry, struct dentry *lower,
+ struct dentry *upper)
+{
+ int err;
+
+ 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);
+
+ ovl_drop_write(dentry);
+ return err;
+}
+
+struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
+ unsigned int flags)
+{
+ struct ovl_entry *oe;
+ const struct cred *old_cred;
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+ struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
+ struct ovl_path *stack = NULL, *origin_path = NULL;
+ struct dentry *upperdir, *upperdentry = NULL;
+ struct dentry *origin = NULL;
+ struct dentry *index = NULL;
+ unsigned int ctr = 0;
+ struct inode *inode = NULL;
+ bool upperopaque = false;
+ char *upperredirect = NULL;
+ struct dentry *this;
+ unsigned int i;
+ int err;
+ bool metacopy = false;
+ struct ovl_lookup_data d = {
+ .sb = dentry->d_sb,
+ .name = dentry->d_name,
+ .is_dir = false,
+ .opaque = false,
+ .stop = false,
+ .last = ofs->config.redirect_follow ? false : !poe->numlower,
+ .redirect = NULL,
+ .metacopy = false,
+ };
+
+ if (dentry->d_name.len > ofs->namelen)
+ return ERR_PTR(-ENAMETOOLONG);
+
+ old_cred = ovl_override_creds(dentry->d_sb);
+ upperdir = ovl_dentry_upper(dentry->d_parent);
+ if (upperdir) {
+ err = ovl_lookup_layer(upperdir, &d, &upperdentry);
+ if (err)
+ goto out;
+
+ if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
+ dput(upperdentry);
+ err = -EREMOTE;
+ goto out;
+ }
+ if (upperdentry && !d.is_dir) {
+ unsigned int origin_ctr = 0;
+
+ /*
+ * Lookup copy up origin by decoding origin file handle.
+ * We may get a disconnected dentry, which is fine,
+ * because we only need to hold the origin inode in
+ * cache and use its inode number. We may even get a
+ * connected dentry, that is not under any of the lower
+ * layers root. That is also fine for using it's inode
+ * 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(ofs, upperdentry, &origin_path,
+ &origin_ctr);
+ if (err)
+ goto out_put_upper;
+
+ if (d.metacopy)
+ metacopy = true;
+ }
+
+ if (d.redirect) {
+ err = -ENOMEM;
+ upperredirect = kstrdup(d.redirect, GFP_KERNEL);
+ if (!upperredirect)
+ goto out_put_upper;
+ if (d.redirect[0] == '/')
+ poe = roe;
+ }
+ upperopaque = d.opaque;
+ }
+
+ if (!d.stop && poe->numlower) {
+ err = -ENOMEM;
+ stack = kcalloc(ofs->numlower, sizeof(struct ovl_path),
+ GFP_KERNEL);
+ if (!stack)
+ goto out_put_upper;
+ }
+
+ for (i = 0; !d.stop && i < poe->numlower; i++) {
+ struct ovl_path lower = poe->lowerstack[i];
+
+ if (!ofs->config.redirect_follow)
+ d.last = i == poe->numlower - 1;
+ else
+ d.last = lower.layer->idx == roe->numlower;
+
+ err = ovl_lookup_layer(lower.dentry, &d, &this);
+ if (err)
+ goto out_put;
+
+ 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 && d.is_dir) {
+ 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.
+ *
+ * For non-dir dentry, if index=on, then ensure origin
+ * matches the dentry found using path based lookup,
+ * otherwise error out.
+ */
+ if (upperdentry && !ctr &&
+ ((d.is_dir && ovl_verify_lower(dentry->d_sb)) ||
+ (!d.is_dir && ofs->config.index && origin_path))) {
+ err = ovl_verify_origin(upperdentry, this, false);
+ if (err) {
+ dput(this);
+ if (d.is_dir)
+ break;
+ goto out_put;
+ }
+ 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) {
+ dput(this);
+ continue;
+ }
+
+ 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.
+ * This is only a problem if the upper layer is untrusted (e.g
+ * comes from an USB drive). This can allow a non-readable file
+ * or directory to become readable.
+ *
+ * Only following redirects when redirects are enabled disables
+ * this attack vector when not necessary.
+ */
+ err = -EPERM;
+ if (d.redirect && !ofs->config.redirect_follow) {
+ pr_warn_ratelimited("overlayfs: refusing to follow redirect for (%pd2)\n",
+ dentry);
+ goto out_put;
+ }
+
+ if (d.stop)
+ break;
+
+ if (d.redirect && d.redirect[0] == '/' && poe != roe) {
+ poe = roe;
+ /* Find the current layer on the root dentry */
+ i = lower.layer->idx - 1;
+ }
+ }
+
+ 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("overlay: refusing to follow metacopy origin for (%pd2)\n",
+ dentry);
+ goto out_put;
+ }
+ } else if (!d.is_dir && upperdentry && !ctr && origin_path) {
+ if (WARN_ON(stack != NULL)) {
+ err = -EIO;
+ goto out_put;
+ }
+ stack = origin_path;
+ ctr = 1;
+ 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.
+ *
+ * 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.
+ *
+ * Always lookup index of non-dir non-metacopy and non-upper.
+ */
+ if (ctr && (!upperdentry || (!d.is_dir && !metacopy)))
+ origin = stack[0].dentry;
+
+ 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;
+ goto out_put;
+ }
+ }
+
+ oe = ovl_alloc_entry(ctr);
+ err = -ENOMEM;
+ if (!oe)
+ goto out_put;
+
+ 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);
+ upperredirect = ovl_get_redirect_xattr(upperdentry, 0);
+ if (IS_ERR(upperredirect)) {
+ err = PTR_ERR(upperredirect);
+ upperredirect = NULL;
+ goto out_free_oe;
+ }
+ }
+
+ if (upperdentry || ctr) {
+ struct ovl_inode_params oip = {
+ .upperdentry = upperdentry,
+ .lowerpath = stack,
+ .index = index,
+ .numlower = ctr,
+ .redirect = upperredirect,
+ .lowerdata = (ctr > 1 && !d.is_dir) ?
+ stack[ctr - 1].dentry : NULL,
+ };
+
+ inode = ovl_get_inode(dentry->d_sb, &oip);
+ err = PTR_ERR(inode);
+ if (IS_ERR(inode))
+ goto out_free_oe;
+ }
+
+ ovl_revert_creds(old_cred);
+ if (origin_path) {
+ dput(origin_path->dentry);
+ kfree(origin_path);
+ }
+ dput(index);
+ kfree(stack);
+ kfree(d.redirect);
+ return d_splice_alias(inode, dentry);
+
+out_free_oe:
+ dentry->d_fsdata = NULL;
+ kfree(oe);
+out_put:
+ dput(index);
+ for (i = 0; i < ctr; i++)
+ dput(stack[i].dentry);
+ kfree(stack);
+out_put_upper:
+ if (origin_path) {
+ dput(origin_path->dentry);
+ kfree(origin_path);
+ }
+ dput(upperdentry);
+ kfree(upperredirect);
+out:
+ kfree(d.redirect);
+ ovl_revert_creds(old_cred);
+ return ERR_PTR(err);
+}
+
+bool ovl_lower_positive(struct dentry *dentry)
+{
+ 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;
+
+ /*
+ * If dentry is negative, then lower is positive iff this is a
+ * whiteout.
+ */
+ if (!dentry->d_inode)
+ 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;
+ struct dentry *lowerdir = poe->lowerstack[i].dentry;
+
+ this = lookup_one_len_unlocked(name->name, lowerdir,
+ name->len);
+ if (IS_ERR(this)) {
+ switch (PTR_ERR(this)) {
+ case -ENOENT:
+ case -ENAMETOOLONG:
+ break;
+
+ default:
+ /*
+ * Assume something is there, we just couldn't
+ * access it.
+ */
+ positive = true;
+ break;
+ }
+ } else {
+ if (this->d_inode) {
+ positive = !ovl_is_whiteout(this);
+ done = true;
+ }
+ dput(this);
+ }
+ }
+ ovl_revert_creds(old_cred);
+
+ return positive;
+}