--- /dev/null
+/*
+ * Minimal file system backend for holding eBPF maps and programs,
+ * used by bpf(2) object pinning.
+ *
+ * Authors:
+ *
+ * Daniel Borkmann <daniel@iogearbox.net>
+ *
+ * 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/module.h>
+#include <linux/magic.h>
+#include <linux/major.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/fs.h>
+#include <linux/kdev_t.h>
+#include <linux/filter.h>
+#include <linux/bpf.h>
+
+enum bpf_type {
+ BPF_TYPE_UNSPEC = 0,
+ BPF_TYPE_PROG,
+ BPF_TYPE_MAP,
+};
+
+static void *bpf_any_get(void *raw, enum bpf_type type)
+{
+ switch (type) {
+ case BPF_TYPE_PROG:
+ atomic_inc(&((struct bpf_prog *)raw)->aux->refcnt);
+ break;
+ case BPF_TYPE_MAP:
+ bpf_map_inc(raw, true);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
+ return raw;
+}
+
+static void bpf_any_put(void *raw, enum bpf_type type)
+{
+ switch (type) {
+ case BPF_TYPE_PROG:
+ bpf_prog_put(raw);
+ break;
+ case BPF_TYPE_MAP:
+ bpf_map_put_with_uref(raw);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+}
+
+static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
+{
+ void *raw;
+
+ *type = BPF_TYPE_MAP;
+ raw = bpf_map_get_with_uref(ufd);
+ if (IS_ERR(raw)) {
+ *type = BPF_TYPE_PROG;
+ raw = bpf_prog_get(ufd);
+ }
+
+ return raw;
+}
+
+static const struct inode_operations bpf_dir_iops;
+
+static const struct inode_operations bpf_prog_iops = { };
+static const struct inode_operations bpf_map_iops = { };
+
+static struct inode *bpf_get_inode(struct super_block *sb,
+ const struct inode *dir,
+ umode_t mode)
+{
+ struct inode *inode;
+
+ switch (mode & S_IFMT) {
+ case S_IFDIR:
+ case S_IFREG:
+ break;
+ default:
+ return ERR_PTR(-EINVAL);
+ }
+
+ inode = new_inode(sb);
+ if (!inode)
+ return ERR_PTR(-ENOSPC);
+
+ inode->i_ino = get_next_ino();
+ inode->i_atime = CURRENT_TIME;
+ inode->i_mtime = inode->i_atime;
+ inode->i_ctime = inode->i_atime;
+
+ inode_init_owner(inode, dir, mode);
+
+ return inode;
+}
+
+static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
+{
+ *type = BPF_TYPE_UNSPEC;
+ if (inode->i_op == &bpf_prog_iops)
+ *type = BPF_TYPE_PROG;
+ else if (inode->i_op == &bpf_map_iops)
+ *type = BPF_TYPE_MAP;
+ else
+ return -EACCES;
+
+ return 0;
+}
+
+static bool bpf_dname_reserved(const struct dentry *dentry)
+{
+ return strchr(dentry->d_name.name, '.');
+}
+
+static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+ struct inode *inode;
+
+ if (bpf_dname_reserved(dentry))
+ return -EPERM;
+
+ inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
+ if (IS_ERR(inode))
+ return PTR_ERR(inode);
+
+ inode->i_op = &bpf_dir_iops;
+ inode->i_fop = &simple_dir_operations;
+
+ inc_nlink(inode);
+ inc_nlink(dir);
+
+ d_instantiate(dentry, inode);
+ dget(dentry);
+
+ return 0;
+}
+
+static int bpf_mkobj_ops(struct inode *dir, struct dentry *dentry,
+ umode_t mode, const struct inode_operations *iops)
+{
+ struct inode *inode;
+
+ if (bpf_dname_reserved(dentry))
+ return -EPERM;
+
+ inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFREG);
+ if (IS_ERR(inode))
+ return PTR_ERR(inode);
+
+ inode->i_op = iops;
+ inode->i_private = dentry->d_fsdata;
+
+ d_instantiate(dentry, inode);
+ dget(dentry);
+
+ return 0;
+}
+
+static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode,
+ dev_t devt)
+{
+ enum bpf_type type = MINOR(devt);
+
+ if (MAJOR(devt) != UNNAMED_MAJOR || !S_ISREG(mode) ||
+ dentry->d_fsdata == NULL)
+ return -EPERM;
+
+ switch (type) {
+ case BPF_TYPE_PROG:
+ return bpf_mkobj_ops(dir, dentry, mode, &bpf_prog_iops);
+ case BPF_TYPE_MAP:
+ return bpf_mkobj_ops(dir, dentry, mode, &bpf_map_iops);
+ default:
+ return -EPERM;
+ }
+}
+
+static const struct inode_operations bpf_dir_iops = {
+ .lookup = simple_lookup,
+ .mknod = bpf_mkobj,
+ .mkdir = bpf_mkdir,
+ .rmdir = simple_rmdir,
+ .unlink = simple_unlink,
+};
+
+static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
+ enum bpf_type type)
+{
+ struct dentry *dentry;
+ struct inode *dir;
+ struct path path;
+ umode_t mode;
+ dev_t devt;
+ int ret;
+
+ dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
+ devt = MKDEV(UNNAMED_MAJOR, type);
+
+ ret = security_path_mknod(&path, dentry, mode, devt);
+ if (ret)
+ goto out;
+
+ dir = d_inode(path.dentry);
+ if (dir->i_op != &bpf_dir_iops) {
+ ret = -EPERM;
+ goto out;
+ }
+
+ dentry->d_fsdata = raw;
+ ret = vfs_mknod(dir, dentry, mode, devt);
+ dentry->d_fsdata = NULL;
+out:
+ done_path_create(&path, dentry);
+ return ret;
+}
+
+int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
+{
+ struct filename *pname;
+ enum bpf_type type;
+ void *raw;
+ int ret;
+
+ pname = getname(pathname);
+ if (IS_ERR(pname))
+ return PTR_ERR(pname);
+
+ raw = bpf_fd_probe_obj(ufd, &type);
+ if (IS_ERR(raw)) {
+ ret = PTR_ERR(raw);
+ goto out;
+ }
+
+ ret = bpf_obj_do_pin(pname, raw, type);
+ if (ret != 0)
+ bpf_any_put(raw, type);
+out:
+ putname(pname);
+ return ret;
+}
+
+static void *bpf_obj_do_get(const struct filename *pathname,
+ enum bpf_type *type)
+{
+ struct inode *inode;
+ struct path path;
+ void *raw;
+ int ret;
+
+ ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
+ if (ret)
+ return ERR_PTR(ret);
+
+ inode = d_backing_inode(path.dentry);
+ ret = inode_permission(inode, MAY_WRITE);
+ if (ret)
+ goto out;
+
+ ret = bpf_inode_type(inode, type);
+ if (ret)
+ goto out;
+
+ raw = bpf_any_get(inode->i_private, *type);
+ touch_atime(&path);
+
+ path_put(&path);
+ return raw;
+out:
+ path_put(&path);
+ return ERR_PTR(ret);
+}
+
+int bpf_obj_get_user(const char __user *pathname)
+{
+ enum bpf_type type = BPF_TYPE_UNSPEC;
+ struct filename *pname;
+ int ret = -ENOENT;
+ void *raw;
+
+ pname = getname(pathname);
+ if (IS_ERR(pname))
+ return PTR_ERR(pname);
+
+ raw = bpf_obj_do_get(pname, &type);
+ if (IS_ERR(raw)) {
+ ret = PTR_ERR(raw);
+ goto out;
+ }
+
+ if (type == BPF_TYPE_PROG)
+ ret = bpf_prog_new_fd(raw);
+ else if (type == BPF_TYPE_MAP)
+ ret = bpf_map_new_fd(raw);
+ else
+ goto out;
+
+ if (ret < 0)
+ bpf_any_put(raw, type);
+out:
+ putname(pname);
+ return ret;
+}
+
+static void bpf_evict_inode(struct inode *inode)
+{
+ enum bpf_type type;
+
+ truncate_inode_pages_final(&inode->i_data);
+ clear_inode(inode);
+
+ if (!bpf_inode_type(inode, &type))
+ bpf_any_put(inode->i_private, type);
+}
+
+static const struct super_operations bpf_super_ops = {
+ .statfs = simple_statfs,
+ .drop_inode = generic_delete_inode,
+ .evict_inode = bpf_evict_inode,
+};
+
+static int bpf_fill_super(struct super_block *sb, void *data, int silent)
+{
+ static struct tree_descr bpf_rfiles[] = { { "" } };
+ struct inode *inode;
+ int ret;
+
+ ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
+ if (ret)
+ return ret;
+
+ sb->s_op = &bpf_super_ops;
+
+ inode = sb->s_root->d_inode;
+ inode->i_op = &bpf_dir_iops;
+ inode->i_mode &= ~S_IALLUGO;
+ inode->i_mode |= S_ISVTX | S_IRWXUGO;
+
+ return 0;
+}
+
+static struct dentry *bpf_mount(struct file_system_type *type, int flags,
+ const char *dev_name, void *data)
+{
+ return mount_ns(type, flags, current->nsproxy->mnt_ns, bpf_fill_super);
+}
+
+static struct file_system_type bpf_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "bpf",
+ .mount = bpf_mount,
+ .kill_sb = kill_litter_super,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+MODULE_ALIAS_FS("bpf");
+
+static int __init bpf_init(void)
+{
+ int ret;
+
+ ret = sysfs_create_mount_point(fs_kobj, "bpf");
+ if (ret)
+ return ret;
+
+ ret = register_filesystem(&bpf_fs_type);
+ if (ret)
+ sysfs_remove_mount_point(fs_kobj, "bpf");
+
+ return ret;
+}
+fs_initcall(bpf_init);
Code Review / kvmfornfv.git / blobdiff