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-rw-r--r--fs/overlayfs/inode.c425
1 files changed, 425 insertions, 0 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
new file mode 100644
index 000000000000..af2d18c9fcee
--- /dev/null
+++ b/fs/overlayfs/inode.c
@@ -0,0 +1,425 @@
+/*
+ *
+ * Copyright (C) 2011 Novell 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/slab.h>
+#include <linux/xattr.h>
+#include "overlayfs.h"
+
+static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr,
+ bool no_data)
+{
+ int err;
+ struct dentry *parent;
+ struct kstat stat;
+ struct path lowerpath;
+
+ parent = dget_parent(dentry);
+ err = ovl_copy_up(parent);
+ if (err)
+ goto out_dput_parent;
+
+ ovl_path_lower(dentry, &lowerpath);
+ err = vfs_getattr(&lowerpath, &stat);
+ if (err)
+ goto out_dput_parent;
+
+ if (no_data)
+ stat.size = 0;
+
+ err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr);
+
+out_dput_parent:
+ dput(parent);
+ return err;
+}
+
+int ovl_setattr(struct dentry *dentry, struct iattr *attr)
+{
+ int err;
+ struct dentry *upperdentry;
+
+ err = ovl_want_write(dentry);
+ if (err)
+ goto out;
+
+ upperdentry = ovl_dentry_upper(dentry);
+ if (upperdentry) {
+ mutex_lock(&upperdentry->d_inode->i_mutex);
+ err = notify_change(upperdentry, attr, NULL);
+ mutex_unlock(&upperdentry->d_inode->i_mutex);
+ } else {
+ err = ovl_copy_up_last(dentry, attr, false);
+ }
+ ovl_drop_write(dentry);
+out:
+ return err;
+}
+
+static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
+ struct kstat *stat)
+{
+ struct path realpath;
+
+ ovl_path_real(dentry, &realpath);
+ return vfs_getattr(&realpath, stat);
+}
+
+int ovl_permission(struct inode *inode, int mask)
+{
+ struct ovl_entry *oe;
+ struct dentry *alias = NULL;
+ struct inode *realinode;
+ struct dentry *realdentry;
+ bool is_upper;
+ int err;
+
+ if (S_ISDIR(inode->i_mode)) {
+ oe = inode->i_private;
+ } else if (mask & MAY_NOT_BLOCK) {
+ return -ECHILD;
+ } else {
+ /*
+ * For non-directories find an alias and get the info
+ * from there.
+ */
+ alias = d_find_any_alias(inode);
+ if (WARN_ON(!alias))
+ return -ENOENT;
+
+ oe = alias->d_fsdata;
+ }
+
+ realdentry = ovl_entry_real(oe, &is_upper);
+
+ /* Careful in RCU walk mode */
+ realinode = ACCESS_ONCE(realdentry->d_inode);
+ if (!realinode) {
+ WARN_ON(!(mask & MAY_NOT_BLOCK));
+ err = -ENOENT;
+ goto out_dput;
+ }
+
+ if (mask & MAY_WRITE) {
+ umode_t mode = realinode->i_mode;
+
+ /*
+ * Writes will always be redirected to upper layer, so
+ * ignore lower layer being read-only.
+ *
+ * If the overlay itself is read-only then proceed
+ * with the permission check, don't return EROFS.
+ * This will only happen if this is the lower layer of
+ * another overlayfs.
+ *
+ * If upper fs becomes read-only after the overlay was
+ * constructed return EROFS to prevent modification of
+ * upper layer.
+ */
+ err = -EROFS;
+ if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
+ (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+ goto out_dput;
+ }
+
+ err = __inode_permission(realinode, mask);
+out_dput:
+ dput(alias);
+ return err;
+}
+
+
+struct ovl_link_data {
+ struct dentry *realdentry;
+ void *cookie;
+};
+
+static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+ void *ret;
+ struct dentry *realdentry;
+ struct inode *realinode;
+
+ realdentry = ovl_dentry_real(dentry);
+ realinode = realdentry->d_inode;
+
+ if (WARN_ON(!realinode->i_op->follow_link))
+ return ERR_PTR(-EPERM);
+
+ ret = realinode->i_op->follow_link(realdentry, nd);
+ if (IS_ERR(ret))
+ return ret;
+
+ if (realinode->i_op->put_link) {
+ struct ovl_link_data *data;
+
+ data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
+ if (!data) {
+ realinode->i_op->put_link(realdentry, nd, ret);
+ return ERR_PTR(-ENOMEM);
+ }
+ data->realdentry = realdentry;
+ data->cookie = ret;
+
+ return data;
+ } else {
+ return NULL;
+ }
+}
+
+static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
+{
+ struct inode *realinode;
+ struct ovl_link_data *data = c;
+
+ if (!data)
+ return;
+
+ realinode = data->realdentry->d_inode;
+ realinode->i_op->put_link(data->realdentry, nd, data->cookie);
+ kfree(data);
+}
+
+static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
+{
+ struct path realpath;
+ struct inode *realinode;
+
+ ovl_path_real(dentry, &realpath);
+ realinode = realpath.dentry->d_inode;
+
+ if (!realinode->i_op->readlink)
+ return -EINVAL;
+
+ touch_atime(&realpath);
+
+ return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
+}
+
+
+static bool ovl_is_private_xattr(const char *name)
+{
+ return strncmp(name, "trusted.overlay.", 14) == 0;
+}
+
+int ovl_setxattr(struct dentry *dentry, const char *name,
+ const void *value, size_t size, int flags)
+{
+ int err;
+ struct dentry *upperdentry;
+
+ err = ovl_want_write(dentry);
+ if (err)
+ goto out;
+
+ err = -EPERM;
+ if (ovl_is_private_xattr(name))
+ goto out_drop_write;
+
+ err = ovl_copy_up(dentry);
+ if (err)
+ goto out_drop_write;
+
+ upperdentry = ovl_dentry_upper(dentry);
+ err = vfs_setxattr(upperdentry, name, value, size, flags);
+
+out_drop_write:
+ ovl_drop_write(dentry);
+out:
+ return err;
+}
+
+ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
+ void *value, size_t size)
+{
+ if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
+ ovl_is_private_xattr(name))
+ return -ENODATA;
+
+ return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
+}
+
+ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+ ssize_t res;
+ int off;
+
+ res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
+ if (res <= 0 || size == 0)
+ return res;
+
+ if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
+ return res;
+
+ /* filter out private xattrs */
+ for (off = 0; off < res;) {
+ char *s = list + off;
+ size_t slen = strlen(s) + 1;
+
+ BUG_ON(off + slen > res);
+
+ if (ovl_is_private_xattr(s)) {
+ res -= slen;
+ memmove(s, s + slen, res - off);
+ } else {
+ off += slen;
+ }
+ }
+
+ return res;
+}
+
+int ovl_removexattr(struct dentry *dentry, const char *name)
+{
+ int err;
+ struct path realpath;
+ enum ovl_path_type type;
+
+ err = ovl_want_write(dentry);
+ if (err)
+ goto out;
+
+ if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
+ ovl_is_private_xattr(name))
+ goto out_drop_write;
+
+ type = ovl_path_real(dentry, &realpath);
+ if (type == OVL_PATH_LOWER) {
+ err = vfs_getxattr(realpath.dentry, name, NULL, 0);
+ if (err < 0)
+ goto out_drop_write;
+
+ err = ovl_copy_up(dentry);
+ if (err)
+ goto out_drop_write;
+
+ ovl_path_upper(dentry, &realpath);
+ }
+
+ err = vfs_removexattr(realpath.dentry, name);
+out_drop_write:
+ ovl_drop_write(dentry);
+out:
+ return err;
+}
+
+static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
+ struct dentry *realdentry)
+{
+ if (type != OVL_PATH_LOWER)
+ return false;
+
+ if (special_file(realdentry->d_inode->i_mode))
+ return false;
+
+ if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
+ return false;
+
+ return true;
+}
+
+static int ovl_dentry_open(struct dentry *dentry, struct file *file,
+ const struct cred *cred)
+{
+ int err;
+ struct path realpath;
+ enum ovl_path_type type;
+ bool want_write = false;
+
+ type = ovl_path_real(dentry, &realpath);
+ if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
+ want_write = true;
+ err = ovl_want_write(dentry);
+ if (err)
+ goto out;
+
+ if (file->f_flags & O_TRUNC)
+ err = ovl_copy_up_last(dentry, NULL, true);
+ else
+ err = ovl_copy_up(dentry);
+ if (err)
+ goto out_drop_write;
+
+ ovl_path_upper(dentry, &realpath);
+ }
+
+ err = vfs_open(&realpath, file, cred);
+out_drop_write:
+ if (want_write)
+ ovl_drop_write(dentry);
+out:
+ return err;
+}
+
+static const struct inode_operations ovl_file_inode_operations = {
+ .setattr = ovl_setattr,
+ .permission = ovl_permission,
+ .getattr = ovl_getattr,
+ .setxattr = ovl_setxattr,
+ .getxattr = ovl_getxattr,
+ .listxattr = ovl_listxattr,
+ .removexattr = ovl_removexattr,
+ .dentry_open = ovl_dentry_open,
+};
+
+static const struct inode_operations ovl_symlink_inode_operations = {
+ .setattr = ovl_setattr,
+ .follow_link = ovl_follow_link,
+ .put_link = ovl_put_link,
+ .readlink = ovl_readlink,
+ .getattr = ovl_getattr,
+ .setxattr = ovl_setxattr,
+ .getxattr = ovl_getxattr,
+ .listxattr = ovl_listxattr,
+ .removexattr = ovl_removexattr,
+};
+
+struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
+ struct ovl_entry *oe)
+{
+ struct inode *inode;
+
+ inode = new_inode(sb);
+ if (!inode)
+ return NULL;
+
+ mode &= S_IFMT;
+
+ inode->i_ino = get_next_ino();
+ inode->i_mode = mode;
+ inode->i_flags |= S_NOATIME | S_NOCMTIME;
+
+ switch (mode) {
+ case S_IFDIR:
+ inode->i_private = oe;
+ inode->i_op = &ovl_dir_inode_operations;
+ inode->i_fop = &ovl_dir_operations;
+ break;
+
+ case S_IFLNK:
+ inode->i_op = &ovl_symlink_inode_operations;
+ break;
+
+ case S_IFREG:
+ case S_IFSOCK:
+ case S_IFBLK:
+ case S_IFCHR:
+ case S_IFIFO:
+ inode->i_op = &ovl_file_inode_operations;
+ break;
+
+ default:
+ WARN(1, "illegal file type: %i\n", mode);
+ iput(inode);
+ inode = NULL;
+ }
+
+ return inode;
+
+}