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;
+
+}