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-rw-r--r--fs/overlayfs/namei.c401
1 files changed, 401 insertions, 0 deletions
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
new file mode 100644
index 000000000000..9ad48d9202a9
--- /dev/null
+++ b/fs/overlayfs/namei.c
@@ -0,0 +1,401 @@
+/*
+ * 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/namei.h>
+#include <linux/xattr.h>
+#include <linux/ratelimit.h>
+#include "overlayfs.h"
+#include "ovl_entry.h"
+
+struct ovl_lookup_data {
+ struct qstr name;
+ bool is_dir;
+ bool opaque;
+ bool stop;
+ bool last;
+ char *redirect;
+};
+
+static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
+ size_t prelen, const char *post)
+{
+ int res;
+ char *s, *next, *buf = NULL;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
+ if (res < 0) {
+ if (res == -ENODATA || res == -EOPNOTSUPP)
+ return 0;
+ goto fail;
+ }
+ buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY);
+ if (!buf)
+ return -ENOMEM;
+
+ if (res == 0)
+ goto invalid;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
+ if (res < 0)
+ goto fail;
+ if (res == 0)
+ goto invalid;
+ if (buf[0] == '/') {
+ for (s = buf; *s++ == '/'; s = next) {
+ next = strchrnul(s, '/');
+ if (s == next)
+ goto invalid;
+ }
+ } else {
+ if (strchr(buf, '/') != NULL)
+ goto invalid;
+
+ 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;
+
+err_free:
+ kfree(buf);
+ return 0;
+fail:
+ pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
+ goto err_free;
+invalid:
+ pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
+ goto err_free;
+}
+
+static bool ovl_is_opaquedir(struct dentry *dentry)
+{
+ int res;
+ char val;
+
+ if (!d_is_dir(dentry))
+ return false;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
+ if (res == 1 && val == 'y')
+ return true;
+
+ return false;
+}
+
+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;
+
+ 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;
+ }
+ if (!d_can_lookup(this)) {
+ d->stop = true;
+ if (d->is_dir)
+ goto put_and_out;
+ goto out;
+ }
+ d->is_dir = true;
+ if (!d->last && ovl_is_opaquedir(this)) {
+ d->stop = 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)
+{
+ const char *s = d->name.name;
+ struct dentry *dentry = NULL;
+ int err;
+
+ if (*s != '/')
+ return ovl_lookup_single(base, d, d->name.name, d->name.len,
+ 0, "", ret);
+
+ while (*s++ == '/' && !IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
+ const char *next = strchrnul(s, '/');
+ size_t slen = strlen(s);
+
+ if (WARN_ON(slen > d->name.len) ||
+ WARN_ON(strcmp(d->name.name + d->name.len - slen, s)))
+ return -EIO;
+
+ err = ovl_lookup_single(base, d, s, next - s,
+ d->name.len - slen, next, &base);
+ dput(dentry);
+ if (err)
+ return err;
+ dentry = base;
+ s = next;
+ }
+ *ret = dentry;
+ return 0;
+}
+
+/*
+ * 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 = oe->lowerstack[idx - 1];
+
+ return (idx < oe->numlower) ? idx + 1 : -1;
+}
+
+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 path *stack = NULL;
+ struct dentry *upperdir, *upperdentry = NULL;
+ unsigned int ctr = 0;
+ struct inode *inode = NULL;
+ bool upperopaque = false;
+ char *upperredirect = NULL;
+ struct dentry *this;
+ unsigned int i;
+ int err;
+ struct ovl_lookup_data d = {
+ .name = dentry->d_name,
+ .is_dir = false,
+ .opaque = false,
+ .stop = false,
+ .last = !poe->numlower,
+ .redirect = NULL,
+ };
+
+ if (dentry->d_name.len > ofs->namelen)
+ return ERR_PTR(-ENAMETOOLONG);
+
+ old_cred = ovl_override_creds(dentry->d_sb);
+ upperdir = ovl_upperdentry_dereference(poe);
+ 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 (d.redirect) {
+ upperredirect = kstrdup(d.redirect, GFP_KERNEL);
+ if (!upperredirect)
+ goto out_put_upper;
+ if (d.redirect[0] == '/')
+ poe = dentry->d_sb->s_root->d_fsdata;
+ }
+ upperopaque = d.opaque;
+ }
+
+ if (!d.stop && poe->numlower) {
+ err = -ENOMEM;
+ stack = kcalloc(ofs->numlower, sizeof(struct path),
+ GFP_TEMPORARY);
+ if (!stack)
+ goto out_put_upper;
+ }
+
+ for (i = 0; !d.stop && i < poe->numlower; i++) {
+ struct path lowerpath = poe->lowerstack[i];
+
+ d.last = i == poe->numlower - 1;
+ err = ovl_lookup_layer(lowerpath.dentry, &d, &this);
+ if (err)
+ goto out_put;
+
+ if (!this)
+ continue;
+
+ stack[ctr].dentry = this;
+ stack[ctr].mnt = lowerpath.mnt;
+ ctr++;
+
+ if (d.stop)
+ break;
+
+ if (d.redirect &&
+ d.redirect[0] == '/' &&
+ poe != dentry->d_sb->s_root->d_fsdata) {
+ poe = dentry->d_sb->s_root->d_fsdata;
+
+ /* Find the current layer on the root dentry */
+ for (i = 0; i < poe->numlower; i++)
+ if (poe->lowerstack[i].mnt == lowerpath.mnt)
+ break;
+ if (WARN_ON(i == poe->numlower))
+ break;
+ }
+ }
+
+ oe = ovl_alloc_entry(ctr);
+ err = -ENOMEM;
+ if (!oe)
+ goto out_put;
+
+ if (upperdentry || ctr) {
+ struct dentry *realdentry;
+ struct inode *realinode;
+
+ realdentry = upperdentry ? upperdentry : stack[0].dentry;
+ realinode = d_inode(realdentry);
+
+ err = -ENOMEM;
+ if (upperdentry && !d_is_dir(upperdentry)) {
+ inode = ovl_get_inode(dentry->d_sb, realinode);
+ } else {
+ inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
+ realinode->i_rdev);
+ if (inode)
+ ovl_inode_init(inode, realinode, !!upperdentry);
+ }
+ if (!inode)
+ goto out_free_oe;
+ ovl_copyattr(realdentry->d_inode, inode);
+ }
+
+ revert_creds(old_cred);
+ oe->opaque = upperopaque;
+ oe->redirect = upperredirect;
+ oe->__upperdentry = upperdentry;
+ memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
+ kfree(stack);
+ kfree(d.redirect);
+ dentry->d_fsdata = oe;
+ d_add(dentry, inode);
+
+ return NULL;
+
+out_free_oe:
+ kfree(oe);
+out_put:
+ for (i = 0; i < ctr; i++)
+ dput(stack[i].dentry);
+ kfree(stack);
+out_put_upper:
+ dput(upperdentry);
+ kfree(upperredirect);
+out:
+ kfree(d.redirect);
+ revert_creds(old_cred);
+ return ERR_PTR(err);
+}
+
+bool ovl_lower_positive(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+ const struct qstr *name = &dentry->d_name;
+ 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 oe->opaque;
+
+ /* Negative upper -> positive lower */
+ if (!oe->__upperdentry)
+ return true;
+
+ /* 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);
+ }
+ }
+
+ return positive;
+}