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dbec2846 EB |
1 | /* |
2 | * This program is free software; you can redistribute it and/or | |
3 | * modify it under the terms of the GNU General Public License as | |
4 | * published by the Free Software Foundation, version 2 of the | |
5 | * License. | |
6 | */ | |
7 | ||
8 | #include <linux/stat.h> | |
9 | #include <linux/sysctl.h> | |
10 | #include <linux/slab.h> | |
11 | #include <linux/user_namespace.h> | |
12 | ||
13 | #ifdef CONFIG_SYSCTL | |
14 | static struct ctl_table_set * | |
15 | set_lookup(struct ctl_table_root *root) | |
16 | { | |
17 | return ¤t_user_ns()->set; | |
18 | } | |
19 | ||
20 | static int set_is_seen(struct ctl_table_set *set) | |
21 | { | |
22 | return ¤t_user_ns()->set == set; | |
23 | } | |
24 | ||
25 | static int set_permissions(struct ctl_table_header *head, | |
26 | struct ctl_table *table) | |
27 | { | |
28 | struct user_namespace *user_ns = | |
29 | container_of(head->set, struct user_namespace, set); | |
30 | int mode; | |
31 | ||
32 | /* Allow users with CAP_SYS_RESOURCE unrestrained access */ | |
33 | if (ns_capable(user_ns, CAP_SYS_RESOURCE)) | |
34 | mode = (table->mode & S_IRWXU) >> 6; | |
35 | else | |
36 | /* Allow all others at most read-only access */ | |
37 | mode = table->mode & S_IROTH; | |
38 | return (mode << 6) | (mode << 3) | mode; | |
39 | } | |
40 | ||
41 | static struct ctl_table_root set_root = { | |
42 | .lookup = set_lookup, | |
43 | .permissions = set_permissions, | |
44 | }; | |
45 | ||
46 | static struct ctl_table userns_table[] = { | |
47 | { } | |
48 | }; | |
49 | #endif /* CONFIG_SYSCTL */ | |
50 | ||
51 | bool setup_userns_sysctls(struct user_namespace *ns) | |
52 | { | |
53 | #ifdef CONFIG_SYSCTL | |
54 | struct ctl_table *tbl; | |
55 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); | |
56 | tbl = kmemdup(userns_table, sizeof(userns_table), GFP_KERNEL); | |
57 | if (tbl) { | |
58 | ns->sysctls = __register_sysctl_table(&ns->set, "userns", tbl); | |
59 | } | |
60 | if (!ns->sysctls) { | |
61 | kfree(tbl); | |
62 | retire_sysctl_set(&ns->set); | |
63 | return false; | |
64 | } | |
65 | #endif | |
66 | return true; | |
67 | } | |
68 | ||
69 | void retire_userns_sysctls(struct user_namespace *ns) | |
70 | { | |
71 | #ifdef CONFIG_SYSCTL | |
72 | struct ctl_table *tbl; | |
73 | ||
74 | tbl = ns->sysctls->ctl_table_arg; | |
75 | unregister_sysctl_table(ns->sysctls); | |
76 | retire_sysctl_set(&ns->set); | |
77 | kfree(tbl); | |
78 | #endif | |
79 | } | |
80 | ||
81 | static __init int user_namespace_sysctl_init(void) | |
82 | { | |
83 | #ifdef CONFIG_SYSCTL | |
84 | static struct ctl_table_header *userns_header; | |
85 | static struct ctl_table empty[1]; | |
86 | /* | |
87 | * It is necessary to register the userns directory in the | |
88 | * default set so that registrations in the child sets work | |
89 | * properly. | |
90 | */ | |
91 | userns_header = register_sysctl("userns", empty); | |
92 | BUG_ON(!userns_header); | |
93 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); | |
94 | #endif | |
95 | return 0; | |
96 | } | |
97 | subsys_initcall(user_namespace_sysctl_init); | |
98 | ||
99 |