Decide whether devices are on the same seat by uid, not pid

In systemd user sessions, some of a user's processes can exist outside
the scope of any particular session:

└─user.slice
  └─user-1000.slice
    ├─user@1000.service
    │ ├─2089 /lib/systemd/systemd --user
    │ └─dbus.service
    │   ├─ 2233 /usr/bin/dbus-daemon …
    │   ├─ 2297 /usr/lib/gvfs/gvfsd
    │   …
    └─session-2.scope
      ├─ 2102 gnome-session
      ├─ 2376 /usr/bin/gnome-shell
      …

If processes outside sessions don't have access to devices on
those sessions' seats, then gvfsd won't be able to mount devices.
Conversely, there is no privilege boundary between the sessions and
the non-session processes - in particular, the user's processes can
usually ptrace each other and write to each other's configuration
files - so isolating them doesn't make a great deal of sense.

I'm specifically looking for one or more *active* sessions on the
device's seat because in a situation like this:

…
├─ alice
│  ├─ graphical session on seat0, tty7, active
│  └─ system --user
├─ bob
│  ├─ graphical session on seat0, tty8, inactive
│  ├─ graphical session on seat1, active
│  └─ systemd --user
└─ chris
   ├─ ssh session on no seat, active
   └─ systemd --user

the desired behaviour is that alice controls seat0 devices and bob
controls seat1 devices, corresponding to their respective
physically-present locations; bob should not have control over
seat0 devices until he returns to seat0, and chris should not have
control over either.

Despite udisks_daemon_util_on_same_seat being documented,
it is not actually public API or ABI: it is part of libudisks-daemon.la,
which is a convenience library statically linked into udisksd and
the tests. As such, it's harmless to replace it with _on_user_seat.
I'm renaming it in order to force compilation failure if a branch
has other callers for the old semantics; if it was not renamed,
passing a pid_t where a uid_t was expected would have compiled,
but silently produced wrong results.

https://bugs.freedesktop.org/show_bug.cgi?id=89501
https://bugs.debian.org/780004

10 files changed, 36 insertions, 185 deletions

diff --git a/doc/udisks2-sections.txt b/doc/udisks2-sections.txt
index 897f48a..6dfc4b4 100644
--- a/doc/udisks2-sections.txt
+++ b/doc/udisks2-sections.txt
@@ -389,7 +389,7 @@ udisks_daemon_util_uninhibit_system_sync
 udisks_daemon_util_hexdump
 udisks_daemon_util_hexdump_debug
 udisks_daemon_util_file_set_contents
-udisks_daemon_util_on_same_seat
+udisks_daemon_util_on_user_seat
 udisks_daemon_util_get_free_mdraid_device
 udisks_ata_identify_get_word
 </SECTION>
diff --git a/src/udisksdaemonutil.c b/src/udisksdaemonutil.c
index 278cf20..1ba7959 100644
--- a/src/udisksdaemonutil.c
+++ b/src/udisksdaemonutil.c
@@ -1038,22 +1038,23 @@ udisks_daemon_util_escape (const gchar *str)
 }
 
 /**
- * udisks_daemon_util_on_same_seat:
+ * udisks_daemon_util_on_user_seat:
  * @daemon: A #UDisksDaemon.
  * @object: The #GDBusObject that the call is on or %NULL.
- * @process: The process to check for.
+ * @user: The user to check for.
  *
  * Checks whether the device represented by @object (if any) is plugged into
- * a seat where the caller represented by @process is logged in.
+ * a seat where the caller represented by @user is logged in and active.
  *
  * This works if @object is a drive or a block object.
  *
- * Returns: %TRUE if @object and @process is on the same seat, %FALSE otherwise.
+ * Returns: %TRUE if @object is on the same seat as one of @user's
+ *  active sessions, %FALSE otherwise.
  */
 gboolean
-udisks_daemon_util_on_same_seat (UDisksDaemon          *daemon,
+udisks_daemon_util_on_user_seat (UDisksDaemon          *daemon,
                                  UDisksObject          *object,
-                                 pid_t                  process)
+                                 uid_t                  user)
 {
 #if !defined(HAVE_LIBSYSTEMD_LOGIN)
   /* if we don't have systemd, assume it's always the same seat */
@@ -1094,16 +1095,9 @@ udisks_daemon_util_on_same_seat (UDisksDaemon          *daemon,
   if (drive == NULL)
     goto out;
 
-  /* It's not unexpected to not find a session, nor a seat associated with @process */
-  if (sd_pid_get_session (process, &session) == 0)
-    sd_session_get_seat (session, &seat);
-
-  /* If we don't know the seat of the caller, we assume the device is always on another seat */
-  if (seat == NULL)
-    goto out;
-
   drive_seat = udisks_drive_get_seat (drive);
-  if (g_strcmp0 (seat, drive_seat) == 0)
+
+  if (drive_seat != NULL && sd_uid_is_on_seat (user, TRUE, drive_seat) > 0)
     {
       ret = TRUE;
       goto out;
diff --git a/src/udisksdaemonutil.h b/src/udisksdaemonutil.h
index 1f2fac1..031812f 100644
--- a/src/udisksdaemonutil.h
+++ b/src/udisksdaemonutil.h
@@ -44,9 +44,9 @@ gboolean udisks_daemon_util_setup_by_user (UDisksDaemon *daemon,
                                            UDisksObject *object,
                                            uid_t         user);
 
-gboolean udisks_daemon_util_on_same_seat (UDisksDaemon          *daemon,
+gboolean udisks_daemon_util_on_user_seat (UDisksDaemon          *daemon,
                                           UDisksObject          *object,
-                                          pid_t                  process);
+                                          uid_t                  user);
 
 gboolean udisks_daemon_util_check_authorization_sync (UDisksDaemon          *daemon,
                                                       UDisksObject          *object,
@@ -87,10 +87,6 @@ gboolean udisks_daemon_util_file_set_contents (const gchar  *filename,
 UDisksInhibitCookie *udisks_daemon_util_inhibit_system_sync   (const gchar          *reason);
 void                 udisks_daemon_util_uninhibit_system_sync (UDisksInhibitCookie  *cookie);
 
-gboolean udisks_daemon_util_on_same_seat (UDisksDaemon          *daemon,
-                                          UDisksObject          *object,
-                                          pid_t                  process);
-
 gchar *udisks_daemon_util_get_free_mdraid_device (void);
 
 guint16 udisks_ata_identify_get_word (const guchar *identify_data, guint word_number);
diff --git a/src/udiskslinuxblock.c b/src/udiskslinuxblock.c
index 9443e17..9e29a9a 100644
--- a/src/udiskslinuxblock.c
+++ b/src/udiskslinuxblock.c
@@ -2176,7 +2176,6 @@ handle_format (UDisksBlock           *block,
   int status;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   gboolean take_ownership = FALSE;
   gchar *encrypt_passphrase = NULL;
   gchar *erase_type = NULL;
@@ -2231,18 +2230,6 @@ handle_format (UDisksBlock           *block,
     }
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon, invocation, NULL /* GCancellable */, &caller_uid, &caller_gid, NULL, &error))
     {
       g_dbus_method_invocation_return_gerror (invocation, error);
@@ -2280,7 +2267,7 @@ handle_format (UDisksBlock           *block,
             {
               action_id = "org.freedesktop.udisks2.modify-device-system";
             }
-          else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+          else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
             {
               action_id = "org.freedesktop.udisks2.modify-device-other-seat";
             }
diff --git a/src/udiskslinuxdrive.c b/src/udiskslinuxdrive.c
index b84204c..cc2695a 100644
--- a/src/udiskslinuxdrive.c
+++ b/src/udiskslinuxdrive.c
@@ -958,7 +958,6 @@ handle_eject (UDisksDrive           *_drive,
   gchar *escaped_device = NULL;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
 
   object = udisks_daemon_util_dup_object (drive, &error);
   if (object == NULL)
@@ -988,18 +987,6 @@ handle_eject (UDisksDrive           *_drive,
     }
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -1025,7 +1012,7 @@ handle_eject (UDisksDrive           *_drive,
     {
       action_id = "org.freedesktop.udisks2.eject-media-system";
     }
-  else if (!udisks_daemon_util_on_same_seat (daemon, UDISKS_OBJECT (object), caller_pid))
+  else if (!udisks_daemon_util_on_user_seat (daemon, UDISKS_OBJECT (object), caller_uid))
     {
       action_id = "org.freedesktop.udisks2.eject-media-other-seat";
     }
@@ -1350,7 +1337,6 @@ handle_power_off (UDisksDrive           *_drive,
   gchar *escaped_device = NULL;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   GList *sibling_objects = NULL, *l;
   gint fd = -1;
 
@@ -1405,18 +1391,6 @@ handle_power_off (UDisksDrive           *_drive,
     }
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -1442,7 +1416,7 @@ handle_power_off (UDisksDrive           *_drive,
     {
       action_id = "org.freedesktop.udisks2.power-off-drive-system";
     }
-  else if (!udisks_daemon_util_on_same_seat (daemon, UDISKS_OBJECT (object), caller_pid))
+  else if (!udisks_daemon_util_on_user_seat (daemon, UDISKS_OBJECT (object), caller_uid))
     {
       action_id = "org.freedesktop.udisks2.power-off-drive-other-seat";
     }
diff --git a/src/udiskslinuxdriveata.c b/src/udiskslinuxdriveata.c
index 84c0e86..63a29f2 100644
--- a/src/udiskslinuxdriveata.c
+++ b/src/udiskslinuxdriveata.c
@@ -1336,7 +1336,7 @@ handle_pm_standby (UDisksDriveAta        *_drive,
   GError *error = NULL;
   const gchar *message;
   const gchar *action_id;
-  pid_t caller_pid;
+  uid_t caller_uid;
 
   object = udisks_daemon_util_dup_object (drive, &error);
   if (object == NULL)
@@ -1369,10 +1369,12 @@ handle_pm_standby (UDisksDriveAta        *_drive,
     }
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
+  if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
-                                               &caller_pid,
+                                               &caller_uid,
+                                               NULL,
+                                               NULL,
                                                &error))
     {
       g_dbus_method_invocation_return_gerror (invocation, error);
@@ -1392,7 +1394,7 @@ handle_pm_standby (UDisksDriveAta        *_drive,
     {
       action_id = "org.freedesktop.udisks2.ata-standby-system";
     }
-  else if (!udisks_daemon_util_on_same_seat (daemon, UDISKS_OBJECT (object), caller_pid))
+  else if (!udisks_daemon_util_on_user_seat (daemon, UDISKS_OBJECT (object), caller_uid))
     {
       action_id = "org.freedesktop.udisks2.ata-standby-other-seat";
     }
@@ -1467,8 +1469,8 @@ handle_pm_wakeup (UDisksDriveAta        *_drive,
   GError *error = NULL;
   const gchar *message;
   const gchar *action_id;
-  pid_t caller_pid;
   guchar buf[4096];
+  uid_t caller_uid;
 
   object = udisks_daemon_util_dup_object (drive, &error);
   if (object == NULL)
@@ -1501,10 +1503,12 @@ handle_pm_wakeup (UDisksDriveAta        *_drive,
     }
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
+  if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
-                                               &caller_pid,
+                                               &caller_uid,
+                                               NULL,
+                                               NULL,
                                                &error))
     {
       g_dbus_method_invocation_return_gerror (invocation, error);
@@ -1524,7 +1528,7 @@ handle_pm_wakeup (UDisksDriveAta        *_drive,
     {
       action_id = "org.freedesktop.udisks2.ata-standby-system";
     }
-  else if (!udisks_daemon_util_on_same_seat (daemon, UDISKS_OBJECT (object), caller_pid))
+  else if (!udisks_daemon_util_on_user_seat (daemon, UDISKS_OBJECT (object), caller_uid))
     {
       action_id = "org.freedesktop.udisks2.ata-standby-other-seat";
     }
diff --git a/src/udiskslinuxencrypted.c b/src/udiskslinuxencrypted.c
index dfee074..fefcba5 100644
--- a/src/udiskslinuxencrypted.c
+++ b/src/udiskslinuxencrypted.c
@@ -247,7 +247,6 @@ handle_unlock (UDisksEncrypted        *encrypted,
   UDisksLinuxDevice *cleartext_device = NULL;
   GError *error = NULL;
   uid_t caller_uid;
-  pid_t caller_pid;
   const gchar *action_id;
   const gchar *message;
   gboolean is_in_crypttab = FALSE;
@@ -314,18 +313,6 @@ handle_unlock (UDisksEncrypted        *encrypted,
       goto out;
     }
 
-  error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
   /* check if in crypttab file */
   error = NULL;
   if (!check_crypttab (block,
@@ -360,7 +347,7 @@ handle_unlock (UDisksEncrypted        *encrypted,
         {
           action_id = "org.freedesktop.udisks2.encrypted-unlock-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.encrypted-unlock-other-seat";
         }
diff --git a/src/udiskslinuxfilesystem.c b/src/udiskslinuxfilesystem.c
index bb47337..eb109dd 100644
--- a/src/udiskslinuxfilesystem.c
+++ b/src/udiskslinuxfilesystem.c
@@ -1147,7 +1147,6 @@ handle_mount (UDisksFilesystem       *filesystem,
   UDisksState *state;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   const gchar * const *existing_mount_points;
   const gchar *probed_fs_usage;
   gchar *fs_type_to_use;
@@ -1235,18 +1234,6 @@ handle_mount (UDisksFilesystem       *filesystem,
       goto out;
     }
 
-  error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
   if (system_managed)
     {
       gint status;
@@ -1268,7 +1255,7 @@ handle_mount (UDisksFilesystem       *filesystem,
                 {
                   action_id = "org.freedesktop.udisks2.filesystem-mount-system";
                 }
-              else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+              else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
                 {
                   action_id = "org.freedesktop.udisks2.filesystem-mount-other-seat";
                 }
@@ -1430,7 +1417,7 @@ handle_mount (UDisksFilesystem       *filesystem,
         {
           action_id = "org.freedesktop.udisks2.filesystem-mount-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.filesystem-mount-other-seat";
         }
@@ -1845,7 +1832,6 @@ handle_set_label (UDisksFilesystem       *filesystem,
   gchar *real_label = NULL;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   gchar *command;
   gchar *tmp;
   GError *error;
@@ -1866,18 +1852,6 @@ handle_set_label (UDisksFilesystem       *filesystem,
   block = udisks_object_peek_block (object);
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -1976,7 +1950,7 @@ handle_set_label (UDisksFilesystem       *filesystem,
         {
           action_id = "org.freedesktop.udisks2.modify-device-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, UDISKS_OBJECT (object), caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, UDISKS_OBJECT (object), caller_uid))
         {
           action_id = "org.freedesktop.udisks2.modify-device-other-seat";
         }
diff --git a/src/udiskslinuxpartition.c b/src/udiskslinuxpartition.c
index 8f0b5cf..bfee216 100644
--- a/src/udiskslinuxpartition.c
+++ b/src/udiskslinuxpartition.c
@@ -227,7 +227,6 @@ handle_set_flags (UDisksPartition        *partition,
   gint fd = -1;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   GError *error;
 
   error = NULL;
@@ -242,18 +241,6 @@ handle_set_flags (UDisksPartition        *partition,
   block = udisks_object_get_block (object);
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -285,7 +272,7 @@ handle_set_flags (UDisksPartition        *partition,
         {
           action_id = "org.freedesktop.udisks2.modify-device-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.modify-device-other-seat";
         }
@@ -392,7 +379,6 @@ handle_set_name (UDisksPartition        *partition,
   gint fd = -1;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   GError *error;
 
   error = NULL;
@@ -407,18 +393,6 @@ handle_set_name (UDisksPartition        *partition,
   block = udisks_object_get_block (object);
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -450,7 +424,7 @@ handle_set_name (UDisksPartition        *partition,
         {
           action_id = "org.freedesktop.udisks2.modify-device-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.modify-device-other-seat";
         }
@@ -734,7 +708,6 @@ handle_set_type (UDisksPartition        *partition,
   UDisksBlock *partition_table_block = NULL;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   GError *error;
 
   error = NULL;
@@ -749,18 +722,6 @@ handle_set_type (UDisksPartition        *partition,
   block = udisks_object_get_block (object);
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -792,7 +753,7 @@ handle_set_type (UDisksPartition        *partition,
         {
           action_id = "org.freedesktop.udisks2.modify-device-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.modify-device-other-seat";
         }
@@ -845,7 +806,6 @@ handle_delete (UDisksPartition        *partition,
   gchar *command_line = NULL;
   uid_t caller_uid;
   gid_t caller_gid;
-  pid_t caller_pid;
   GError *error;
 
   error = NULL;
@@ -860,18 +820,6 @@ handle_delete (UDisksPartition        *partition,
   block = udisks_object_get_block (object);
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -903,7 +851,7 @@ handle_delete (UDisksPartition        *partition,
         {
           action_id = "org.freedesktop.udisks2.modify-device-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.modify-device-other-seat";
         }
diff --git a/src/udiskslinuxpartitiontable.c b/src/udiskslinuxpartitiontable.c
index 17fa518..2692b31 100644
--- a/src/udiskslinuxpartitiontable.c
+++ b/src/udiskslinuxpartitiontable.c
@@ -340,7 +340,6 @@ handle_create_partition (UDisksPartitionTable   *table,
   UDisksBlock *partition_block = NULL;
   gchar *escaped_partition_device = NULL;
   const gchar *table_type;
-  pid_t caller_pid;
   uid_t caller_uid;
   gid_t caller_gid;
   gboolean do_wipe = TRUE;
@@ -364,18 +363,6 @@ handle_create_partition (UDisksPartitionTable   *table,
     }
 
   error = NULL;
-  if (!udisks_daemon_util_get_caller_pid_sync (daemon,
-                                               invocation,
-                                               NULL /* GCancellable */,
-                                               &caller_pid,
-                                               &error))
-    {
-      g_dbus_method_invocation_return_gerror (invocation, error);
-      g_error_free (error);
-      goto out;
-    }
-
-  error = NULL;
   if (!udisks_daemon_util_get_caller_uid_sync (daemon,
                                                invocation,
                                                NULL /* GCancellable */,
@@ -403,7 +390,7 @@ handle_create_partition (UDisksPartitionTable   *table,
         {
           action_id = "org.freedesktop.udisks2.modify-device-system";
         }
-      else if (!udisks_daemon_util_on_same_seat (daemon, object, caller_pid))
+      else if (!udisks_daemon_util_on_user_seat (daemon, object, caller_uid))
         {
           action_id = "org.freedesktop.udisks2.modify-device-other-seat";
         }