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  * Version 2 capabilities worked fine, but the linux/capability.h file
  57  * that accompanied their introduction encouraged their use without
  58  * the necessary user-space source code changes. As such, we have
  59  * created a version 3 with equivalent functionality to version 2, but
  60  * with a header change to protect legacy source code from using
  61  * version 2 when it wanted to use version 1. If your system has code
  62  * that trips the following warning, it is using version 2 specific
  63  * capabilities and may be doing so insecurely.
  64  *
  65  * The remedy is to either upgrade your version of libcap (to 2.10+,
  66  * if the application is linked against it), or recompile your
  67  * application with modern kernel headers and this warning will go
  68  * away.
  69  */
  70
  71 static void warn_deprecated_v2(void)
  72 {
  73         static int warned;
  74
  75         if (!warned) {
  76                 char name[sizeof(current->comm)];
  77
  78                 printk(KERN_INFO "warning: `%s' uses deprecated v2"
  79                        " capabilities in a way that may be insecure.\n",
  80                        get_task_comm(name, current));
  81                 warned = 1;
  82         }
  83 }
  84
  85 /*
  86  * Version check. Return the number of u32s in each capability flag
  87  * array, or a negative value on error.
  88  */
  89 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
  90 {
  91         __u32 version;
  92
  93         if (get_user(version, &header->version))
  94                 return -EFAULT;
  95
  96         switch (version) {
  97         case _LINUX_CAPABILITY_VERSION_1:
  98                 warn_legacy_capability_use();
  99                 *tocopy = _LINUX_CAPABILITY_U32S_1;
 100                 break;
 101         case _LINUX_CAPABILITY_VERSION_2:
 102                 warn_deprecated_v2();
 103                 /*
 104                  * fall through - v3 is otherwise equivalent to v2.
 105                  */
 106         case _LINUX_CAPABILITY_VERSION_3:
 107                 *tocopy = _LINUX_CAPABILITY_U32S_3;
 108                 break;
 109         default:
 110                 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
 111                         return -EFAULT;
 112                 return -EINVAL;
 113         }
 114
 115         return 0;
 116 }
 117
 118 /*
 119  * For sys_getproccap() and sys_setproccap(), any of the three
 120  * capability set pointers may be NULL -- indicating that that set is
 121  * uninteresting and/or not to be changed.
 122  */
 123
 124 /**
 125  * sys_capget - get the capabilities of a given process.
 126  * @header: pointer to struct that contains capability version and
 127  *      target pid data
 128  * @dataptr: pointer to struct that contains the effective, permitted,
 129  *      and inheritable capabilities that are returned
 130  *
 131  * Returns 0 on success and < 0 on error.
 132  */
 133 asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
 134 {
 135         int ret = 0;
 136         pid_t pid;
 137         struct task_struct *target;
 138         unsigned tocopy;
 139         kernel_cap_t pE, pI, pP;
 140
 141         ret = cap_validate_magic(header, &tocopy);
 142         if (ret != 0)
 143                 return ret;
 144
 145         if (get_user(pid, &header->pid))
 146                 return -EFAULT;
 147
 148         if (pid < 0)
 149                 return -EINVAL;
 150
 151         spin_lock(&task_capability_lock);
 152         read_lock(&tasklist_lock);
 153
 154         if (pid && pid != task_pid_vnr(current)) {
 155                 target = find_task_by_vpid(pid);
 156                 if (!target) {
 157                         ret = -ESRCH;
 158                         goto out;
 159                 }
 160         } else
 161                 target = current;
 162
 163         ret = security_capget(target, &pE, &pI, &pP);
 164
 165 out:
 166         read_unlock(&tasklist_lock);
 167         spin_unlock(&task_capability_lock);
 168
 169         if (!ret) {
 170                 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 171                 unsigned i;
 172
 173                 for (i = 0; i < tocopy; i++) {
 174                         kdata[i].effective = pE.cap[i];
 175                         kdata[i].permitted = pP.cap[i];
 176                         kdata[i].inheritable = pI.cap[i];
 177                 }
 178
 179                 /*
 180                  * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
 181                  * we silently drop the upper capabilities here. This
 182                  * has the effect of making older libcap
 183                  * implementations implicitly drop upper capability
 184                  * bits when they perform a: capget/modify/capset
 185                  * sequence.
 186                  *
 187                  * This behavior is considered fail-safe
 188                  * behavior. Upgrading the application to a newer
 189                  * version of libcap will enable access to the newer
 190                  * capabilities.
 191                  *
 192                  * An alternative would be to return an error here
 193                  * (-ERANGE), but that causes legacy applications to
 194                  * unexpectidly fail; the capget/modify/capset aborts
 195                  * before modification is attempted and the application
 196                  * fails.
 197                  */
 198
 199                 if (copy_to_user(dataptr, kdata, tocopy
 200                                  * sizeof(struct __user_cap_data_struct))) {
 201                         return -EFAULT;
 202                 }
 203         }
 204
 205         return ret;
 206 }
 207
 208 /*
 209  * cap_set_pg - set capabilities for all processes in a given process
 210  * group.  We call this holding task_capability_lock and tasklist_lock.
 211  */
 212 static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
 213                               kernel_cap_t *inheritable,
 214                               kernel_cap_t *permitted)
 215 {
 216         struct task_struct *g, *target;
 217         int ret = -EPERM;
 218         int found = 0;
 219         struct pid *pgrp;
 220
 221         pgrp = find_vpid(pgrp_nr);
 222         do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
 223                 target = g;
 224                 while_each_thread(g, target) {
 225                         if (!security_capset_check(target, effective,
 226                                                         inheritable,
 227                                                         permitted)) {
 228                                 security_capset_set(target, effective,
 229                                                         inheritable,
 230                                                         permitted);
 231                                 ret = 0;
 232                         }
 233                         found = 1;
 234                 }
 235         } while_each_pid_task(pgrp, PIDTYPE_PGID, g);
 236
 237         if (!found)
 238                 ret = 0;
 239         return ret;
 240 }
 241
 242 /*
 243  * cap_set_all - set capabilities for all processes other than init
 244  * and self.  We call this holding task_capability_lock and tasklist_lock.
 245  */
 246 static inline int cap_set_all(kernel_cap_t *effective,
 247                                kernel_cap_t *inheritable,
 248                                kernel_cap_t *permitted)
 249 {
 250      struct task_struct *g, *target;
 251      int ret = -EPERM;
 252      int found = 0;
 253
 254      do_each_thread(g, target) {
 255              if (target == current || is_container_init(target->group_leader))
 256                      continue;
 257              found = 1;
 258              if (security_capset_check(target, effective, inheritable,
 259                                                 permitted))
 260                      continue;
 261              ret = 0;
 262              security_capset_set(target, effective, inheritable, permitted);
 263      } while_each_thread(g, target);
 264
 265      if (!found)
 266              ret = 0;
 267      return ret;
 268 }
 269
 270 /**
 271  * sys_capset - set capabilities for a process or a group of processes
 272  * @header: pointer to struct that contains capability version and
 273  *      target pid data
 274  * @data: pointer to struct that contains the effective, permitted,
 275  *      and inheritable capabilities
 276  *
 277  * Set capabilities for a given process, all processes, or all
 278  * processes in a given process group.
 279  *
 280  * The restrictions on setting capabilities are specified as:
 281  *
 282  * [pid is for the 'target' task.  'current' is the calling task.]
 283  *
 284  * I: any raised capabilities must be a subset of the (old current) permitted
 285  * P: any raised capabilities must be a subset of the (old current) permitted
 286  * E: must be set to a subset of (new target) permitted
 287  *
 288  * Returns 0 on success and < 0 on error.
 289  */
 290 asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
 291 {
 292         struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 293         unsigned i, tocopy;
 294         kernel_cap_t inheritable, permitted, effective;
 295         struct task_struct *target;
 296         int ret;
 297         pid_t pid;
 298
 299         ret = cap_validate_magic(header, &tocopy);
 300         if (ret != 0)
 301                 return ret;
 302
 303         if (get_user(pid, &header->pid))
 304                 return -EFAULT;
 305
 306         if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
 307                 return -EPERM;
 308
 309         if (copy_from_user(&kdata, data, tocopy
 310                            * sizeof(struct __user_cap_data_struct))) {
 311                 return -EFAULT;
 312         }
 313
 314         for (i = 0; i < tocopy; i++) {
 315                 effective.cap[i] = kdata[i].effective;
 316                 permitted.cap[i] = kdata[i].permitted;
 317                 inheritable.cap[i] = kdata[i].inheritable;
 318         }
 319         while (i < _KERNEL_CAPABILITY_U32S) {
 320                 effective.cap[i] = 0;
 321                 permitted.cap[i] = 0;
 322                 inheritable.cap[i] = 0;
 323                 i++;
 324         }
 325
 326         spin_lock(&task_capability_lock);
 327         read_lock(&tasklist_lock);
 328
 329         if (pid > 0 && pid != task_pid_vnr(current)) {
 330                 target = find_task_by_vpid(pid);
 331                 if (!target) {
 332                         ret = -ESRCH;
 333                         goto out;
 334                 }
 335         } else
 336                 target = current;
 337
 338         ret = 0;
 339
 340         /* having verified that the proposed changes are legal,
 341            we now put them into effect. */
 342         if (pid < 0) {
 343                 if (pid == -1)  /* all procs other than current and init */
 344                         ret = cap_set_all(&effective, &inheritable, &permitted);
 345
 346                 else            /* all procs in process group */
 347                         ret = cap_set_pg(-pid, &effective, &inheritable,
 348                                          &permitted);
 349         } else {
 350                 ret = security_capset_check(target, &effective, &inheritable,
 351                                             &permitted);
 352                 if (!ret)
 353                         security_capset_set(target, &effective, &inheritable,
 354                                             &permitted);
 355         }
 356
 357 out:
 358         read_unlock(&tasklist_lock);
 359         spin_unlock(&task_capability_lock);
 360
 361         return ret;
 362 }
 363
 364 int __capable(struct task_struct *t, int cap)
 365 {
 366         if (security_capable(t, cap) == 0) {
 367                 t->flags |= PF_SUPERPRIV;
 368                 return 1;
 369         }
 370         return 0;
 371 }
 372
 373 int capable(int cap)
 374 {
 375         return __capable(current, cap);
 376 }
 377 EXPORT_SYMBOL(capable);