src/login/logind-session-device.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2013 David Herrmann
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <fcntl.h>
  21 #include <linux/input.h>
  22 #include <string.h>
  23 #include <sys/ioctl.h>
  24 #include <sys/types.h>
  25
  26 #include "libudev.h"
  27
  28 #include "alloc-util.h"
  29 #include "bus-util.h"
  30 #include "fd-util.h"
  31 #include "logind-session-device.h"
  32 #include "missing.h"
  33 #include "parse-util.h"
  34 #include "sd-daemon.h"
  35 #include "util.h"
  36
  37 enum SessionDeviceNotifications {
  38         SESSION_DEVICE_RESUME,
  39         SESSION_DEVICE_TRY_PAUSE,
  40         SESSION_DEVICE_PAUSE,
  41         SESSION_DEVICE_RELEASE,
  42 };
  43
  44 static int session_device_notify(SessionDevice *sd, enum SessionDeviceNotifications type) {
  45         _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
  46         _cleanup_free_ char *path = NULL;
  47         const char *t = NULL;
  48         uint32_t major, minor;
  49         int r;
  50
  51         assert(sd);
  52
  53         major = major(sd->dev);
  54         minor = minor(sd->dev);
  55
  56         if (!sd->session->controller)
  57                 return 0;
  58
  59         path = session_bus_path(sd->session);
  60         if (!path)
  61                 return -ENOMEM;
  62
  63         r = sd_bus_message_new_signal(
  64                         sd->session->manager->bus,
  65                         &m, path,
  66                         "org.freedesktop.login1.Session",
  67                         (type == SESSION_DEVICE_RESUME) ? "ResumeDevice" : "PauseDevice");
  68         if (!m)
  69                 return r;
  70
  71         r = sd_bus_message_set_destination(m, sd->session->controller);
  72         if (r < 0)
  73                 return r;
  74
  75         switch (type) {
  76         case SESSION_DEVICE_RESUME:
  77                 r = sd_bus_message_append(m, "uuh", major, minor, sd->fd);
  78                 if (r < 0)
  79                         return r;
  80                 break;
  81         case SESSION_DEVICE_TRY_PAUSE:
  82                 t = "pause";
  83                 break;
  84         case SESSION_DEVICE_PAUSE:
  85                 t = "force";
  86                 break;
  87         case SESSION_DEVICE_RELEASE:
  88                 t = "gone";
  89                 break;
  90         default:
  91                 return -EINVAL;
  92         }
  93
  94         if (t) {
  95                 r = sd_bus_message_append(m, "uus", major, minor, t);
  96                 if (r < 0)
  97                         return r;
  98         }
  99
 100         return sd_bus_send(sd->session->manager->bus, m, NULL);
 101 }
 102
 103 static int sd_eviocrevoke(int fd) {
 104         static bool warned;
 105         int r;
 106
 107         assert(fd >= 0);
 108
 109         r = ioctl(fd, EVIOCREVOKE, NULL);
 110         if (r < 0) {
 111                 r = -errno;
 112                 if (r == -EINVAL && !warned) {
 113                         warned = true;
 114                         log_warning("kernel does not support evdev-revocation");
 115                 }
 116         }
 117
 118         return 0;
 119 }
 120
 121 static int sd_drmsetmaster(int fd) {
 122         int r;
 123
 124         assert(fd >= 0);
 125
 126         r = ioctl(fd, DRM_IOCTL_SET_MASTER, 0);
 127         if (r < 0)
 128                 return -errno;
 129
 130         return 0;
 131 }
 132
 133 static int sd_drmdropmaster(int fd) {
 134         int r;
 135
 136         assert(fd >= 0);
 137
 138         r = ioctl(fd, DRM_IOCTL_DROP_MASTER, 0);
 139         if (r < 0)
 140                 return -errno;
 141
 142         return 0;
 143 }
 144
 145 static int session_device_open(SessionDevice *sd, bool active) {
 146         int fd, r;
 147
 148         assert(sd->type != DEVICE_TYPE_UNKNOWN);
 149
 150         /* open device and try to get an udev_device from it */
 151         fd = open(sd->node, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
 152         if (fd < 0)
 153                 return -errno;
 154
 155         switch (sd->type) {
 156         case DEVICE_TYPE_DRM:
 157                 if (active) {
 158                         /* Weird legacy DRM semantics might return an error
 159                          * even though we're master. No way to detect that so
 160                          * fail at all times and let caller retry in inactive
 161                          * state. */
 162                         r = sd_drmsetmaster(fd);
 163                         if (r < 0) {
 164                                 close_nointr(fd);
 165                                 return r;
 166                         }
 167                 } else {
 168                         /* DRM-Master is granted to the first user who opens a
 169                          * device automatically (ughh, racy!). Hence, we just
 170                          * drop DRM-Master in case we were the first. */
 171                         sd_drmdropmaster(fd);
 172                 }
 173                 break;
 174         case DEVICE_TYPE_EVDEV:
 175                 if (!active)
 176                         sd_eviocrevoke(fd);
 177                 break;
 178         case DEVICE_TYPE_UNKNOWN:
 179         default:
 180                 /* fallback for devices wihout synchronizations */
 181                 break;
 182         }
 183
 184         return fd;
 185 }
 186
 187 static int session_device_start(SessionDevice *sd) {
 188         int r;
 189
 190         assert(sd);
 191         assert(session_is_active(sd->session));
 192
 193         if (sd->active)
 194                 return 0;
 195
 196         switch (sd->type) {
 197         case DEVICE_TYPE_DRM:
 198                 /* Device is kept open. Simply call drmSetMaster() and hope
 199                  * there is no-one else. In case it fails, we keep the device
 200                  * paused. Maybe at some point we have a drmStealMaster(). */
 201                 r = sd_drmsetmaster(sd->fd);
 202                 if (r < 0)
 203                         return r;
 204                 break;
 205         case DEVICE_TYPE_EVDEV:
 206                 /* Evdev devices are revoked while inactive. Reopen it and we
 207                  * are fine. */
 208                 r = session_device_open(sd, true);
 209                 if (r < 0)
 210                         return r;
 211                 /* For evdev devices, the file descriptor might be left
 212                  * uninitialized. This might happen while resuming into a
 213                  * session and logind has been restarted right before. */
 214                 safe_close(sd->fd);
 215                 sd->fd = r;
 216                 break;
 217         case DEVICE_TYPE_UNKNOWN:
 218         default:
 219                 /* fallback for devices wihout synchronizations */
 220                 break;
 221         }
 222
 223         sd->active = true;
 224         return 0;
 225 }
 226
 227 static void session_device_stop(SessionDevice *sd) {
 228         assert(sd);
 229
 230         if (!sd->active)
 231                 return;
 232
 233         switch (sd->type) {
 234         case DEVICE_TYPE_DRM:
 235                 /* On DRM devices we simply drop DRM-Master but keep it open.
 236                  * This allows the user to keep resources allocated. The
 237                  * CAP_SYS_ADMIN restriction to DRM-Master prevents users from
 238                  * circumventing this. */
 239                 sd_drmdropmaster(sd->fd);
 240                 break;
 241         case DEVICE_TYPE_EVDEV:
 242                 /* Revoke access on evdev file-descriptors during deactivation.
 243                  * This will basically prevent any operations on the fd and
 244                  * cannot be undone. Good side is: it needs no CAP_SYS_ADMIN
 245                  * protection this way. */
 246                 sd_eviocrevoke(sd->fd);
 247                 break;
 248         case DEVICE_TYPE_UNKNOWN:
 249         default:
 250                 /* fallback for devices without synchronization */
 251                 break;
 252         }
 253
 254         sd->active = false;
 255 }
 256
 257 static DeviceType detect_device_type(struct udev_device *dev) {
 258         const char *sysname, *subsystem;
 259         DeviceType type;
 260
 261         sysname = udev_device_get_sysname(dev);
 262         subsystem = udev_device_get_subsystem(dev);
 263         type = DEVICE_TYPE_UNKNOWN;
 264
 265         if (streq_ptr(subsystem, "drm")) {
 266                 if (startswith(sysname, "card"))
 267                         type = DEVICE_TYPE_DRM;
 268         } else if (streq_ptr(subsystem, "input")) {
 269                 if (startswith(sysname, "event"))
 270                         type = DEVICE_TYPE_EVDEV;
 271         }
 272
 273         return type;
 274 }
 275
 276 static int session_device_verify(SessionDevice *sd) {
 277         struct udev_device *dev, *p = NULL;
 278         const char *sp, *node;
 279         int r;
 280
 281         dev = udev_device_new_from_devnum(sd->session->manager->udev, 'c', sd->dev);
 282         if (!dev)
 283                 return -ENODEV;
 284
 285         sp = udev_device_get_syspath(dev);
 286         node = udev_device_get_devnode(dev);
 287         if (!node) {
 288                 r = -EINVAL;
 289                 goto err_dev;
 290         }
 291
 292         /* detect device type so we can find the correct sysfs parent */
 293         sd->type = detect_device_type(dev);
 294         if (sd->type == DEVICE_TYPE_UNKNOWN) {
 295                 r = -ENODEV;
 296                 goto err_dev;
 297         } else if (sd->type == DEVICE_TYPE_EVDEV) {
 298                 /* for evdev devices we need the parent node as device */
 299                 p = dev;
 300                 dev = udev_device_get_parent_with_subsystem_devtype(p, "input", NULL);
 301                 if (!dev) {
 302                         r = -ENODEV;
 303                         goto err_dev;
 304                 }
 305                 sp = udev_device_get_syspath(dev);
 306         } else if (sd->type != DEVICE_TYPE_DRM) {
 307                 /* Prevent opening unsupported devices. Especially devices of
 308                  * subsystem "input" must be opened via the evdev node as
 309                  * we require EVIOCREVOKE. */
 310                 r = -ENODEV;
 311                 goto err_dev;
 312         }
 313
 314         /* search for an existing seat device and return it if available */
 315         sd->device = hashmap_get(sd->session->manager->devices, sp);
 316         if (!sd->device) {
 317                 /* The caller might have gotten the udev event before we were
 318                  * able to process it. Hence, fake the "add" event and let the
 319                  * logind-manager handle the new device. */
 320                 r = manager_process_seat_device(sd->session->manager, dev);
 321                 if (r < 0)
 322                         goto err_dev;
 323
 324                 /* if it's still not available, then the device is invalid */
 325                 sd->device = hashmap_get(sd->session->manager->devices, sp);
 326                 if (!sd->device) {
 327                         r = -ENODEV;
 328                         goto err_dev;
 329                 }
 330         }
 331
 332         if (sd->device->seat != sd->session->seat) {
 333                 r = -EPERM;
 334                 goto err_dev;
 335         }
 336
 337         sd->node = strdup(node);
 338         if (!sd->node) {
 339                 r = -ENOMEM;
 340                 goto err_dev;
 341         }
 342
 343         r = 0;
 344 err_dev:
 345         udev_device_unref(p ? : dev);
 346         return r;
 347 }
 348
 349 int session_device_new(Session *s, dev_t dev, bool open_device, SessionDevice **out) {
 350         SessionDevice *sd;
 351         int r;
 352
 353         assert(s);
 354         assert(out);
 355
 356         if (!s->seat)
 357                 return -EPERM;
 358
 359         sd = new0(SessionDevice, 1);
 360         if (!sd)
 361                 return -ENOMEM;
 362
 363         sd->session = s;
 364         sd->dev = dev;
 365         sd->fd = -1;
 366         sd->type = DEVICE_TYPE_UNKNOWN;
 367
 368         r = session_device_verify(sd);
 369         if (r < 0)
 370                 goto error;
 371
 372         r = hashmap_put(s->devices, &sd->dev, sd);
 373         if (r < 0) {
 374                 r = -ENOMEM;
 375                 goto error;
 376         }
 377
 378         if (open_device) {
 379                 /* Open the device for the first time. We need a valid fd to pass back
 380                  * to the caller. If the session is not active, this _might_ immediately
 381                  * revoke access and thus invalidate the fd. But this is still needed
 382                  * to pass a valid fd back. */
 383                 sd->active = session_is_active(s);
 384                 r = session_device_open(sd, sd->active);
 385                 if (r < 0) {
 386                         /* EINVAL _may_ mean a master is active; retry inactive */
 387                         if (sd->active && r == -EINVAL) {
 388                                 sd->active = false;
 389                                 r = session_device_open(sd, false);
 390                         }
 391                         if (r < 0)
 392                                 goto error;
 393                 }
 394                 sd->fd = r;
 395         }
 396
 397         LIST_PREPEND(sd_by_device, sd->device->session_devices, sd);
 398
 399         *out = sd;
 400         return 0;
 401
 402 error:
 403         hashmap_remove(s->devices, &sd->dev);
 404         free(sd->node);
 405         free(sd);
 406         return r;
 407 }
 408
 409 void session_device_free(SessionDevice *sd) {
 410         assert(sd);
 411
 412         session_device_stop(sd);
 413         session_device_notify(sd, SESSION_DEVICE_RELEASE);
 414         close_nointr(sd->fd);
 415
 416         LIST_REMOVE(sd_by_device, sd->device->session_devices, sd);
 417
 418         hashmap_remove(sd->session->devices, &sd->dev);
 419
 420         free(sd->node);
 421         free(sd);
 422 }
 423
 424 void session_device_complete_pause(SessionDevice *sd) {
 425         SessionDevice *iter;
 426         Iterator i;
 427
 428         if (!sd->active)
 429                 return;
 430
 431         session_device_stop(sd);
 432
 433         /* if not all devices are paused, wait for further completion events */
 434         HASHMAP_FOREACH(iter, sd->session->devices, i)
 435                 if (iter->active)
 436                         return;
 437
 438         /* complete any pending session switch */
 439         seat_complete_switch(sd->session->seat);
 440 }
 441
 442 void session_device_resume_all(Session *s) {
 443         SessionDevice *sd;
 444         Iterator i;
 445
 446         assert(s);
 447
 448         HASHMAP_FOREACH(sd, s->devices, i) {
 449                 if (!sd->active) {
 450                         if (session_device_start(sd) < 0)
 451                                 continue;
 452                         if (session_device_save(sd) < 0)
 453                                 continue;
 454                         session_device_notify(sd, SESSION_DEVICE_RESUME);
 455                 }
 456         }
 457 }
 458
 459 void session_device_pause_all(Session *s) {
 460         SessionDevice *sd;
 461         Iterator i;
 462
 463         assert(s);
 464
 465         HASHMAP_FOREACH(sd, s->devices, i) {
 466                 if (sd->active) {
 467                         session_device_stop(sd);
 468                         session_device_notify(sd, SESSION_DEVICE_PAUSE);
 469                 }
 470         }
 471 }
 472
 473 unsigned int session_device_try_pause_all(Session *s) {
 474         SessionDevice *sd;
 475         Iterator i;
 476         unsigned int num_pending = 0;
 477
 478         assert(s);
 479
 480         HASHMAP_FOREACH(sd, s->devices, i) {
 481                 if (sd->active) {
 482                         session_device_notify(sd, SESSION_DEVICE_TRY_PAUSE);
 483                         ++num_pending;
 484                 }
 485         }
 486
 487         return num_pending;
 488 }
 489
 490 int session_device_save(SessionDevice *sd) {
 491         _cleanup_free_ char *state = NULL;
 492         int r;
 493
 494         assert(sd);
 495
 496         /* Store device fd in PID1. It will send it back to us on
 497          * restart so revocation will continue to work. To make things
 498          * simple, send fds for all type of devices even if they don't
 499          * support the revocation mechanism so we don't have to handle
 500          * them differently later.
 501          *
 502          * Note: for device supporting revocation, PID1 will drop a
 503          * stored fd automatically if the corresponding device is
 504          * revoked. */
 505         r = asprintf(&state, "FDSTORE=1\n"
 506                              "FDNAME=session-%s", sd->session->id);
 507         if (r < 0)
 508                 return -ENOMEM;
 509
 510         return sd_pid_notify_with_fds(0, false, state, &sd->fd, 1);
 511 }
 512
 513 void session_device_attach_fd(SessionDevice *sd, int fd, bool active) {
 514         assert(fd > 0);
 515         assert(sd);
 516         assert(sd->fd < 0);
 517         assert(!sd->active);
 518
 519         sd->fd = fd;
 520         sd->active = active;
 521 }