kernel/capability.c

   1 /*
   2  * linux/kernel/capability.c
   3  *
   4  * Copyright (C) 1997  Andrew Main <zefram@fysh.org>
   5  *
   6  * Integrated into 2.1.97+,  Andrew G. Morgan <morgan@kernel.org>
   7  * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
   8  */
   9
  10 #include <linux/capability.h>
  11 #include <linux/mm.h>
  12 #include <linux/module.h>
  13 #include <linux/security.h>
  14 #include <linux/syscalls.h>
  15 #include <linux/pid_namespace.h>
  16 #include <asm/uaccess.h>
  17
  18 /*
  19  * This lock protects task->cap_* for all tasks including current.
  20  * Locking rule: acquire this prior to tasklist_lock.
  21  */
  22 static DEFINE_SPINLOCK(task_capability_lock);
  23
  24 /*
  25  * Leveraged for setting/resetting capabilities
  26  */
  27
  28 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
  29 const kernel_cap_t __cap_full_set = CAP_FULL_SET;
  30 const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
  31
  32 EXPORT_SYMBOL(__cap_empty_set);
  33 EXPORT_SYMBOL(__cap_full_set);
  34 EXPORT_SYMBOL(__cap_init_eff_set);
  35
  36 /*
  37  * More recent versions of libcap are available from:
  38  *
  39  *   http://www.kernel.org/pub/linux/libs/security/linux-privs/
  40  */
  41
  42 static void warn_legacy_capability_use(void)
  43 {
  44         static int warned;
  45         if (!warned) {
  46                 char name[sizeof(current->comm)];
  47
  48                 printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
  49                        " (legacy support in use)\n",
  50                        get_task_comm(name, current));
  51                 warned = 1;
  52         }
  53 }
  54
  55 /*
  56  * For sys_getproccap() and sys_setproccap(), any of the three
  57  * capability set pointers may be NULL -- indicating that that set is
  58  * uninteresting and/or not to be changed.
  59  */
  60
  61 /**
  62  * sys_capget - get the capabilities of a given process.
  63  * @header: pointer to struct that contains capability version and
  64  *      target pid data
  65  * @dataptr: pointer to struct that contains the effective, permitted,
  66  *      and inheritable capabilities that are returned
  67  *
  68  * Returns 0 on success and < 0 on error.
  69  */
  70 asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
  71 {
  72         int ret = 0;
  73         pid_t pid;
  74         __u32 version;
  75         struct task_struct *target;
  76         unsigned tocopy;
  77         kernel_cap_t pE, pI, pP;
  78
  79         if (get_user(version, &header->version))
  80                 return -EFAULT;
  81
  82         switch (version) {
  83         case _LINUX_CAPABILITY_VERSION_1:
  84                 warn_legacy_capability_use();
  85                 tocopy = _LINUX_CAPABILITY_U32S_1;
  86                 break;
  87         case _LINUX_CAPABILITY_VERSION_2:
  88                 tocopy = _LINUX_CAPABILITY_U32S_2;
  89                 break;
  90         default:
  91                 if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
  92                         return -EFAULT;
  93                 return -EINVAL;
  94         }
  95
  96         if (get_user(pid, &header->pid))
  97                 return -EFAULT;
  98
  99         if (pid < 0)
 100                 return -EINVAL;
 101
 102         spin_lock(&task_capability_lock);
 103         read_lock(&tasklist_lock);
 104
 105         if (pid && pid != task_pid_vnr(current)) {
 106                 target = find_task_by_vpid(pid);
 107                 if (!target) {
 108                         ret = -ESRCH;
 109                         goto out;
 110                 }
 111         } else
 112                 target = current;
 113
 114         ret = security_capget(target, &pE, &pI, &pP);
 115
 116 out:
 117         read_unlock(&tasklist_lock);
 118         spin_unlock(&task_capability_lock);
 119
 120         if (!ret) {
 121                 struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
 122                 unsigned i;
 123
 124                 for (i = 0; i < tocopy; i++) {
 125                         kdata[i].effective = pE.cap[i];
 126                         kdata[i].permitted = pP.cap[i];
 127                         kdata[i].inheritable = pI.cap[i];
 128                 }
 129
 130                 /*
 131                  * Note, in the case, tocopy < _LINUX_CAPABILITY_U32S,
 132                  * we silently drop the upper capabilities here. This
 133                  * has the effect of making older libcap
 134                  * implementations implicitly drop upper capability
 135                  * bits when they perform a: capget/modify/capset
 136                  * sequence.
 137                  *
 138                  * This behavior is considered fail-safe
 139                  * behavior. Upgrading the application to a newer
 140                  * version of libcap will enable access to the newer
 141                  * capabilities.
 142                  *
 143                  * An alternative would be to return an error here
 144                  * (-ERANGE), but that causes legacy applications to
 145                  * unexpectidly fail; the capget/modify/capset aborts
 146                  * before modification is attempted and the application
 147                  * fails.
 148                  */
 149
 150                 if (copy_to_user(dataptr, kdata, tocopy
 151                                  * sizeof(struct __user_cap_data_struct))) {
 152                         return -EFAULT;
 153                 }
 154         }
 155
 156         return ret;
 157 }
 158
 159 /*
 160  * cap_set_pg - set capabilities for all processes in a given process
 161  * group.  We call this holding task_capability_lock and tasklist_lock.
 162  */
 163 static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
 164                               kernel_cap_t *inheritable,
 165                               kernel_cap_t *permitted)
 166 {
 167         struct task_struct *g, *target;
 168         int ret = -EPERM;
 169         int found = 0;
 170         struct pid *pgrp;
 171
 172         pgrp = find_vpid(pgrp_nr);
 173         do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
 174                 target = g;
 175                 while_each_thread(g, target) {
 176                         if (!security_capset_check(target, effective,
 177                                                         inheritable,
 178                                                         permitted)) {
 179                                 security_capset_set(target, effective,
 180                                                         inheritable,
 181                                                         permitted);
 182                                 ret = 0;
 183                         }
 184                         found = 1;
 185                 }
 186         } while_each_pid_task(pgrp, PIDTYPE_PGID, g);
 187
 188         if (!found)
 189                 ret = 0;
 190         return ret;
 191 }
 192
 193 /*
 194  * cap_set_all - set capabilities for all processes other than init
 195  * and self.  We call this holding task_capability_lock and tasklist_lock.
 196  */
 197 static inline int cap_set_all(kernel_cap_t *effective,
 198                                kernel_cap_t *inheritable,
 199                                kernel_cap_t *permitted)
 200 {
 201      struct task_struct *g, *target;
 202      int ret = -EPERM;
 203      int found = 0;
 204
 205      do_each_thread(g, target) {
 206              if (target == current || is_container_init(target->group_leader))
 207                      continue;
 208              found = 1;
 209              if (security_capset_check(target, effective, inheritable,
 210                                                 permitted))
 211                      continue;
 212              ret = 0;
 213              security_capset_set(target, effective, inheritable, permitted);
 214      } while_each_thread(g, target);
 215
 216      if (!found)
 217              ret = 0;
 218      return ret;
 219 }
 220
 221 /**
 222  * sys_capset - set capabilities for a process or a group of processes
 223  * @header: pointer to struct that contains capability version and
 224  *      target pid data
 225  * @data: pointer to struct that contains the effective, permitted,
 226  *      and inheritable capabilities
 227  *
 228  * Set capabilities for a given process, all processes, or all
 229  * processes in a given process group.
 230  *
 231  * The restrictions on setting capabilities are specified as:
 232  *
 233  * [pid is for the 'target' task.  'current' is the calling task.]
 234  *
 235  * I: any raised capabilities must be a subset of the (old current) permitted
 236  * P: any raised capabilities must be a subset of the (old current) permitted
 237  * E: must be set to a subset of (new target) permitted
 238  *
 239  * Returns 0 on success and < 0 on error.
 240  */
 241 asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
 242 {
 243         struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
 244         unsigned i, tocopy;
 245         kernel_cap_t inheritable, permitted, effective;
 246         __u32 version;
 247         struct task_struct *target;
 248         int ret;
 249         pid_t pid;
 250
 251         if (get_user(version, &header->version))
 252                 return -EFAULT;
 253
 254         switch (version) {
 255         case _LINUX_CAPABILITY_VERSION_1:
 256                 warn_legacy_capability_use();
 257                 tocopy = _LINUX_CAPABILITY_U32S_1;
 258                 break;
 259         case _LINUX_CAPABILITY_VERSION_2:
 260                 tocopy = _LINUX_CAPABILITY_U32S_2;
 261                 break;
 262         default:
 263                 if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
 264                         return -EFAULT;
 265                 return -EINVAL;
 266         }
 267
 268         if (get_user(pid, &header->pid))
 269                 return -EFAULT;
 270
 271         if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
 272                 return -EPERM;
 273
 274         if (copy_from_user(&kdata, data, tocopy
 275                            * sizeof(struct __user_cap_data_struct))) {
 276                 return -EFAULT;
 277         }
 278
 279         for (i = 0; i < tocopy; i++) {
 280                 effective.cap[i] = kdata[i].effective;
 281                 permitted.cap[i] = kdata[i].permitted;
 282                 inheritable.cap[i] = kdata[i].inheritable;
 283         }
 284         while (i < _LINUX_CAPABILITY_U32S) {
 285                 effective.cap[i] = 0;
 286                 permitted.cap[i] = 0;
 287                 inheritable.cap[i] = 0;
 288                 i++;
 289         }
 290
 291         spin_lock(&task_capability_lock);
 292         read_lock(&tasklist_lock);
 293
 294         if (pid > 0 && pid != task_pid_vnr(current)) {
 295                 target = find_task_by_vpid(pid);
 296                 if (!target) {
 297                         ret = -ESRCH;
 298                         goto out;
 299                 }
 300         } else
 301                 target = current;
 302
 303         ret = 0;
 304
 305         /* having verified that the proposed changes are legal,
 306            we now put them into effect. */
 307         if (pid < 0) {
 308                 if (pid == -1)  /* all procs other than current and init */
 309                         ret = cap_set_all(&effective, &inheritable, &permitted);
 310
 311                 else            /* all procs in process group */
 312                         ret = cap_set_pg(-pid, &effective, &inheritable,
 313                                          &permitted);
 314         } else {
 315                 ret = security_capset_check(target, &effective, &inheritable,
 316                                             &permitted);
 317                 if (!ret)
 318                         security_capset_set(target, &effective, &inheritable,
 319                                             &permitted);
 320         }
 321
 322 out:
 323         read_unlock(&tasklist_lock);
 324         spin_unlock(&task_capability_lock);
 325
 326         return ret;
 327 }
 328
 329 int __capable(struct task_struct *t, int cap)
 330 {
 331         if (security_capable(t, cap) == 0) {
 332                 t->flags |= PF_SUPERPRIV;
 333                 return 1;
 334         }
 335         return 0;
 336 }
 337
 338 int capable(int cap)
 339 {
 340         return __capable(current, cap);
 341 }
 342 EXPORT_SYMBOL(capable);