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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Copyright (C) 2011 Novell Inc.
- * Copyright (C) 2016 Red Hat, Inc.
- */
- #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;
- struct ovl_fs *ofs = OVL_FS(d->sb);
- buf = ovl_get_redirect_xattr(ofs, 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_fb_len(struct ovl_fb *fb, int fb_len)
- {
- if (fb_len < sizeof(struct ovl_fb) || fb_len < fb->len)
- return -EINVAL;
- if (fb->magic != OVL_FH_MAGIC)
- return -EINVAL;
- /* Treat larger version and unknown flags as "origin unknown" */
- if (fb->version > OVL_FH_VERSION || fb->flags & ~OVL_FH_FLAG_ALL)
- return -ENODATA;
- /* Treat endianness mismatch as "origin unknown" */
- if (!(fb->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
- (fb->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
- return -ENODATA;
- return 0;
- }
- static struct ovl_fh *ovl_get_fh(struct ovl_fs *ofs, struct dentry *dentry,
- enum ovl_xattr ox)
- {
- ssize_t res;
- int err;
- struct ovl_fh *fh = NULL;
- res = ovl_do_getxattr(ofs, dentry, ox, 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 + OVL_FH_WIRE_OFFSET, GFP_KERNEL);
- if (!fh)
- return ERR_PTR(-ENOMEM);
- res = ovl_do_getxattr(ofs, dentry, ox, fh->buf, res);
- if (res < 0)
- goto fail;
- err = ovl_check_fb_len(&fh->fb, res);
- if (err < 0) {
- if (err == -ENODATA)
- goto out;
- goto invalid;
- }
- return fh;
- out:
- kfree(fh);
- return NULL;
- fail:
- pr_warn_ratelimited("failed to get origin (%zi)\n", res);
- goto out;
- invalid:
- pr_warn_ratelimited("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->fb.uuid, &mnt->mnt_sb->s_uuid))
- return NULL;
- bytes = (fh->fb.len - offsetof(struct ovl_fb, fid));
- real = exportfs_decode_fh(mnt, (struct fid *)fh->fb.fid,
- bytes >> 2, (int)fh->fb.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->fb.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 super_block *sb, struct dentry *dentry)
- {
- return ovl_check_dir_xattr(sb, 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, bool drop_negative)
- {
- struct dentry *this;
- int err;
- bool last_element = !post[0];
- this = ovl_lookup_positive_unlocked(name, base, namelen, drop_negative);
- if (IS_ERR(this)) {
- err = PTR_ERR(this);
- this = NULL;
- if (err == -ENOENT || err == -ENAMETOOLONG)
- goto out;
- goto out_err;
- }
- 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(OVL_FS(d->sb), 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(d->sb, 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, bool drop_negative)
- {
- /* 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, drop_negative);
- 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,
- drop_negative);
- 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 = 1; i < ofs->numlayer; i++) {
- /*
- * If lower fs uuid is not unique among lower fs we cannot match
- * fh->uuid to layer.
- */
- if (ofs->layers[i].fsid &&
- ofs->layers[i].fs->bad_uuid)
- continue;
- origin = ovl_decode_real_fh(fh, ofs->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) &&
- inode_wrong_type(d_inode(upperdentry), d_inode(origin)->i_mode))
- 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->layers[i]
- };
- return 0;
- invalid:
- pr_warn_ratelimited("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)
- {
- struct ovl_fh *fh = ovl_get_fh(ofs, 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;
- }
- 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 ovl_fs *ofs, struct dentry *dentry,
- enum ovl_xattr ox, const struct ovl_fh *fh)
- {
- struct ovl_fh *ofh = ovl_get_fh(ofs, dentry, ox);
- int err = 0;
- if (!ofh)
- return -ENODATA;
- if (IS_ERR(ofh))
- return PTR_ERR(ofh);
- if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.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 ovl_fs *ofs, struct dentry *dentry,
- enum ovl_xattr ox, 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(ofs, dentry, ox, fh);
- if (set && err == -ENODATA)
- err = ovl_do_setxattr(ofs, dentry, ox, fh->buf, fh->fb.len);
- if (err)
- goto fail;
- out:
- kfree(fh);
- return err;
- fail:
- inode = d_inode(real);
- pr_warn_ratelimited("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(ofs, index, OVL_XATTR_UPPER);
- if (IS_ERR_OR_NULL(fh))
- return ERR_CAST(fh);
- upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true);
- kfree(fh);
- if (IS_ERR_OR_NULL(upper))
- return upper ?: ERR_PTR(-ESTALE);
- if (!d_is_dir(upper)) {
- pr_warn_ratelimited("invalid index upper (%pd2, upper=%pd2).\n",
- index, upper);
- dput(upper);
- return ERR_PTR(-EIO);
- }
- return upper;
- }
- /*
- * 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;
- err = -EINVAL;
- if (index->d_name.len < sizeof(struct ovl_fb)*2)
- goto fail;
- err = -ENOMEM;
- len = index->d_name.len / 2;
- fh = kzalloc(len + OVL_FH_WIRE_OFFSET, GFP_KERNEL);
- if (!fh)
- goto fail;
- err = -EINVAL;
- if (hex2bin(fh->buf, index->d_name.name, len))
- goto fail;
- err = ovl_check_fb_len(&fh->fb, 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(ofs, 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(ofs, origin.dentry, index, 0) == 0)
- goto orphan;
- }
- out:
- dput(origin.dentry);
- kfree(fh);
- return err;
- fail:
- pr_warn_ratelimited("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("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->fb.len, 2, GFP_KERNEL);
- if (!n)
- return -ENOMEM;
- s = bin2hex(n, fh->buf, fh->fb.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_positive_unlocked(name.name, ofs->indexdir, name.len);
- kfree(name.name);
- if (IS_ERR(index)) {
- if (PTR_ERR(index) == -ENOENT)
- index = NULL;
- return index;
- }
- 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_positive_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("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 (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_wrong_type(inode, d_inode(origin)->i_mode)) {
- /*
- * 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("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("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(ofs, index, upper, false);
- if (err) {
- if (err == -ESTALE) {
- pr_warn_ratelimited("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 ovl_fs *ofs, struct dentry *dentry,
- struct dentry *lower, struct dentry *upper)
- {
- int err;
- if (ovl_check_origin_xattr(ofs, 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 uppermetacopy = 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, true);
- if (err)
- goto out;
- if (upperdentry && upperdentry->d_flags & DCACHE_OP_REAL) {
- dput(upperdentry);
- err = -EREMOTE;
- goto out;
- }
- if (upperdentry && !d.is_dir) {
- /*
- * 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);
- if (err)
- goto out_put_upper;
- if (d.metacopy)
- uppermetacopy = 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->numlayer - 1, 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, false);
- if (err)
- goto out_put;
- if (!this)
- continue;
- if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) {
- dput(this);
- 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".
- */
- if (upperdentry && !ctr && !ofs->noxattr && d.is_dir) {
- err = ovl_fix_origin(ofs, 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(ofs, upperdentry, this, false);
- if (err) {
- dput(this);
- if (d.is_dir)
- break;
- goto out_put;
- }
- origin = this;
- }
- 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);
- this = NULL;
- } else {
- 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("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;
- }
- }
- /*
- * 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;
- goto out_put;
- }
- stack = origin_path;
- ctr = 1;
- origin = origin_path->dentry;
- origin_path = NULL;
- }
- /*
- * 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 metacopy upper, we set a verified origin already if index
- * is enabled and if upper had an ORIGIN xattr.
- *
- */
- if (!upperdentry && ctr)
- 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(ofs, upperdentry, 0);
- if (IS_ERR(upperredirect)) {
- err = PTR_ERR(upperredirect);
- upperredirect = NULL;
- goto out_free_oe;
- }
- err = ovl_check_metacopy_xattr(ofs, upperdentry);
- if (err < 0)
- goto out_free_oe;
- uppermetacopy = err;
- }
- 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;
- if (upperdentry && !uppermetacopy)
- ovl_set_flag(OVL_UPPERDATA, inode);
- }
- ovl_dentry_update_reval(dentry, upperdentry,
- DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
- ovl_revert_creds(dentry->d_sb, 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(dentry->d_sb, 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_positive_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 {
- positive = !ovl_is_whiteout(this);
- done = true;
- dput(this);
- }
- }
- ovl_revert_creds(dentry->d_sb, old_cred);
- return positive;
- }
|