1/*
2 * linux/kernel/capability.c
3 *
4 * Copyright (C) 1997  Andrew Main <zefram@fysh.org>
5 * Integrated into 2.1.97+,  Andrew G. Morgan <morgan@transmeta.com>
6 */
7
8#include <linux/mm.h>
9#include <asm/uaccess.h>
10
11kernel_cap_t cap_bset = CAP_INIT_EFF_SET;
12
13/* Note: never hold tasklist_lock while spinning for this one */
14spinlock_t task_capability_lock = SPIN_LOCK_UNLOCKED;
15
16/*
17 * For sys_getproccap() and sys_setproccap(), any of the three
18 * capability set pointers may be NULL -- indicating that that set is
19 * uninteresting and/or not to be changed.
20 */
21
22asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
23{
24     int error, pid;
25     __u32 version;
26     struct task_struct *target;
27     struct __user_cap_data_struct data;
28
29     if (get_user(version, &header->version))
30	     return -EFAULT;
31
32     error = -EINVAL;
33     if (version != _LINUX_CAPABILITY_VERSION) {
34             version = _LINUX_CAPABILITY_VERSION;
35	     if (put_user(version, &header->version))
36		     error = -EFAULT;
37             return error;
38     }
39
40     if (get_user(pid, &header->pid))
41	     return -EFAULT;
42
43     if (pid < 0)
44             return -EINVAL;
45
46     error = 0;
47
48     spin_lock(&task_capability_lock);
49
50     if (pid && pid != current->pid) {
51	     read_lock(&tasklist_lock);
52             target = find_task_by_pid(pid);  /* identify target of query */
53             if (!target)
54                     error = -ESRCH;
55     } else {
56             target = current;
57     }
58
59     if (!error) {
60	     data.permitted = cap_t(target->cap_permitted);
61	     data.inheritable = cap_t(target->cap_inheritable);
62	     data.effective = cap_t(target->cap_effective);
63     }
64
65     if (target != current)
66	     read_unlock(&tasklist_lock);
67     spin_unlock(&task_capability_lock);
68
69     if (!error) {
70	     if (copy_to_user(dataptr, &data, sizeof data))
71		     return -EFAULT;
72     }
73
74     return error;
75}
76
77/* set capabilities for all processes in a given process group */
78
79static void cap_set_pg(int pgrp,
80                    kernel_cap_t *effective,
81                    kernel_cap_t *inheritable,
82                    kernel_cap_t *permitted)
83{
84     struct task_struct *target;
85
86     read_lock(&tasklist_lock);
87     for_each_task(target) {
88             if (target->pgrp != pgrp)
89                     continue;
90             target->cap_effective   = *effective;
91             target->cap_inheritable = *inheritable;
92             target->cap_permitted   = *permitted;
93     }
94     read_unlock(&tasklist_lock);
95}
96
97/* set capabilities for all processes other than 1 and self */
98
99static void cap_set_all(kernel_cap_t *effective,
100                     kernel_cap_t *inheritable,
101                     kernel_cap_t *permitted)
102{
103     struct task_struct *target;
104
105     read_lock(&tasklist_lock);
106     /* ALL means everyone other than self or 'init' */
107     for_each_task(target) {
108             if (target == current || target->pid == 1)
109                     continue;
110             target->cap_effective   = *effective;
111             target->cap_inheritable = *inheritable;
112             target->cap_permitted   = *permitted;
113     }
114     read_unlock(&tasklist_lock);
115}
116
117/*
118 * The restrictions on setting capabilities are specified as:
119 *
120 * [pid is for the 'target' task.  'current' is the calling task.]
121 *
122 * I: any raised capabilities must be a subset of the (old current) Permitted
123 * P: any raised capabilities must be a subset of the (old current) permitted
124 * E: must be set to a subset of (new target) Permitted
125 */
126
127asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
128{
129     kernel_cap_t inheritable, permitted, effective;
130     __u32 version;
131     struct task_struct *target;
132     int error, pid;
133
134     if (get_user(version, &header->version))
135	     return -EFAULT;
136
137     if (version != _LINUX_CAPABILITY_VERSION) {
138             version = _LINUX_CAPABILITY_VERSION;
139	     if (put_user(version, &header->version))
140		     return -EFAULT;
141             return -EINVAL;
142     }
143
144     if (get_user(pid, &header->pid))
145	     return -EFAULT;
146
147     if (pid && !capable(CAP_SETPCAP))
148             return -EPERM;
149
150     if (copy_from_user(&effective, &data->effective, sizeof(effective)) ||
151	 copy_from_user(&inheritable, &data->inheritable, sizeof(inheritable)) ||
152	 copy_from_user(&permitted, &data->permitted, sizeof(permitted)))
153	     return -EFAULT;
154
155     error = -EPERM;
156     spin_lock(&task_capability_lock);
157
158     if (pid > 0 && pid != current->pid) {
159             read_lock(&tasklist_lock);
160             target = find_task_by_pid(pid);  /* identify target of query */
161             if (!target) {
162                     error = -ESRCH;
163		     goto out;
164	     }
165     } else {
166             target = current;
167     }
168
169
170     /* verify restrictions on target's new Inheritable set */
171     if (!cap_issubset(inheritable,
172                       cap_combine(target->cap_inheritable,
173                                   current->cap_permitted))) {
174             goto out;
175     }
176
177     /* verify restrictions on target's new Permitted set */
178     if (!cap_issubset(permitted,
179                       cap_combine(target->cap_permitted,
180                                   current->cap_permitted))) {
181             goto out;
182     }
183
184     /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
185     if (!cap_issubset(effective, permitted)) {
186             goto out;
187     }
188
189     /* having verified that the proposed changes are legal,
190           we now put them into effect. */
191     error = 0;
192
193     if (pid < 0) {
194             if (pid == -1)  /* all procs other than current and init */
195                     cap_set_all(&effective, &inheritable, &permitted);
196
197             else            /* all procs in process group */
198                     cap_set_pg(-pid, &effective, &inheritable, &permitted);
199             goto spin_out;
200     } else {
201             target->cap_effective   = effective;
202             target->cap_inheritable = inheritable;
203             target->cap_permitted   = permitted;
204     }
205
206out:
207     if (target != current) {
208             read_unlock(&tasklist_lock);
209     }
210spin_out:
211     spin_unlock(&task_capability_lock);
212     return error;
213}
214