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| 2 | |
| 3 | * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
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| 4 | *
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| 5 | * Copyright (c) 2001-3 Patrick Mochel
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| 6 | * Copyright (c) 2007 SUSE Linux Products GmbH
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| 7 | * Copyright (c) 2007 Tejun Heo <[email protected]>
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| 8 | *
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| 9 | * Please see Documentation/filesystems/sysfs.rst for more information.
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| 10 |
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| 11 |
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| 12 | #include <linux/fs.h>
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| 13 | #include <linux/magic.h>
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| 14 | #include <linux/mount.h>
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| 15 | #include <linux/init.h>
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| 16 | #include <linux/slab.h>
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| 17 | #include <linux/user_namespace.h>
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| 18 | #include <linux/fs_context.h>
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| 19 | #include <net/net_namespace.h>
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| 20 |
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| 21 | #include "sysfs.h"
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| 22 |
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| 23 | static struct kernfs_root *sysfs_root;
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| 24 | struct kernfs_node *sysfs_root_kn;
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| 25 |
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| 26 | static void sysfs_fs_context_free(struct fs_context *fc)
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| 27 | {
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| 28 | struct kernfs_fs_context *kfc = fc->fs_private;
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| 29 |
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| 30 | if (kfc->ns_tag)
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| 31 | kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);
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| 32 | kernfs_free_fs_context(fc);
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| 33 | kfree(kfc);
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| 34 | }
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| 35 |
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| 36 | static const struct fs_context_operations sysfs_fs_context_ops = {
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| 37 | .free = sysfs_fs_context_free,
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| 38 | .get_tree = kernfs_get_tree,
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| 39 | };
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| 40 |
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| 41 | static int sysfs_init_fs_context(struct fs_context *fc)
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| 42 | {
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| 43 | struct kernfs_fs_context *kfc;
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| 44 | struct ns_common *ns;
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| 45 |
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| 46 | if (!(fc->sb_flags & SB_KERNMOUNT)) {
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| 47 | if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
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| 48 | return -EPERM;
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| 49 | }
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| 50 |
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| 51 | kfc = kzalloc_obj(struct kernfs_fs_context);
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| 52 | if (!kfc)
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| 53 | return -ENOMEM;
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| 54 |
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| 55 | kfc->ns_tag = ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
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| 56 | kfc->root = sysfs_root;
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| 57 | kfc->magic = SYSFS_MAGIC;
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| 58 | fc->fs_private = kfc;
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| 59 | fc->ops = &sysfs_fs_context_ops;
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| 60 | if (ns) {
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| 61 | struct net *netns = to_net_ns(ns);
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| 62 |
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| 63 | put_user_ns(fc->user_ns);
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| 64 | fc->user_ns = get_user_ns(netns->user_ns);
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| 65 | }
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| 66 | fc->global = true;
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| 67 | return 0;
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| 68 | }
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| 69 |
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| 70 | static void sysfs_kill_sb(struct super_block *sb)
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| 71 | {
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| 72 | struct ns_common *ns = (struct ns_common *)kernfs_super_ns(sb);
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| 73 |
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| 74 | kernfs_kill_sb(sb);
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| 75 | kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
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| 76 | }
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| 77 |
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| 78 | static struct file_system_type sysfs_fs_type = {
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| 79 | .name = "sysfs",
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| 80 | .init_fs_context = sysfs_init_fs_context,
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| 81 | .kill_sb = sysfs_kill_sb,
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| 82 | .fs_flags = FS_USERNS_MOUNT | FS_USERNS_MOUNT_RESTRICTED,
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| 83 | };
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| 84 |
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| 85 | int __init sysfs_init(void)
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| 86 | {
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| 87 | int err;
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| 88 |
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| 89 | sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
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| 90 | NULL);
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| 91 | if (IS_ERR(sysfs_root))
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| 92 | return PTR_ERR(sysfs_root);
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| 93 |
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| 94 | sysfs_root_kn = kernfs_root_to_node(sysfs_root);
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| 95 |
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| 96 | err = register_filesystem(&sysfs_fs_type);
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| 97 | if (err) {
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| 98 | kernfs_destroy_root(sysfs_root);
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| 99 | return err;
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| 100 | }
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| 101 |
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| 102 | return 0;
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| 103 | }
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