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/*
* Copyright © 2020 Collabora, Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Authors:
* Emil Velikov <emil.l.velikov@gmail.com>
*
*/
/*
* Testcase: Check that drop/setMaster behaves correctly wrt root/user access
*
* Test checks if the ioctls succeed or fail, depending if the applications was
* run with root, user privileges or if we have separate privileged arbitrator.
*/
#include "igt.h"
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
IGT_TEST_DESCRIPTION("Check that Drop/SetMaster behaves correctly wrt root/user"
" access");
static bool is_master(int fd)
{
/* FIXME: replace with drmIsMaster once we bumped libdrm version */
return drmAuthMagic(fd, 0) != -EACCES;
}
static void check_drop_set(void)
{
int master;
master = __drm_open_driver(DRIVER_ANY);
/* Ensure we have a valid device. This is _extremely_ unlikely to
* trigger as tweak_perm() aims to ensure we have the correct rights.
* Although:
* - igt_fork() + igt_skip() is broken, aka the igt_skip() is not
* propagated to the child and we FAIL with a misleading trace.
* - there is _no_ guarantee that we'll open a device handled by
* tweak_perm(), because __drm_open_driver() does a modprobe(8)
* - successfully opening a device is part of the test
*/
igt_assert_neq(master, -1);
/* At this point we're master capable due to:
* - being root - always
* - normal user - as the only drm only drm client (on this VT)
*/
igt_assert_eq(is_master(master), true);
/* If we have SYS_CAP_ADMIN we're in the textbook best-case scenario.
*
* Otherwise newer kernels allow the application to drop/revoke its
* master capability and request it again later.
*
* In this case, we address two types of issues:
* - the application no longer need suid-root (or equivalent) which
* was otherwise required _solely_ for these two ioctls
* - plenty of applications ignore (or discard) the result of the
* calls all together.
*/
igt_assert_eq(drmDropMaster(master), 0);
igt_assert_eq(drmSetMaster(master), 0);
close(master);
}
static unsigned tweak_perm(uint8_t *saved_perm, unsigned max_perm, bool save)
{
char path[256];
struct stat st;
unsigned i;
for (i = 0; i < max_perm; i++) {
snprintf(path, sizeof(path), "/dev/dri/card%u", i);
/* Existing userspace assumes there's no gaps, do the same. */
if (stat(path, &st) != 0)
break;
if (save) {
/* Save and toggle */
saved_perm[i] = st.st_mode & (S_IROTH | S_IWOTH);
st.st_mode |= S_IROTH | S_IWOTH;
} else {
/* Clear and restore */
st.st_mode &= ~(S_IROTH | S_IWOTH);
st.st_mode |= saved_perm[i];
}
/* There's only one way for chmod to fail - race vs rmmod.
* In that case, do _not_ error/skip, since:
* - we need to restore the [correct] permissions
* - __drm_open_driver() can open another device, aka the
* failure may be irrelevant.
*/
chmod(path, st.st_mode);
}
return i;
}
igt_main
{
igt_fixture {
/*
* We're operating on the device files themselves
* before opening them, make sure the drivers are
* loaded.
*/
drm_load_module(DRIVER_ANY);
}
igt_describe("Ensure that root can Set/DropMaster");
igt_subtest("master-drop-set-root") {
check_drop_set();
}
igt_subtest_group {
uint8_t saved_perm[255];
unsigned num;
/* Upon dropping root we end up as random user, which
* a) is not in the video group, and
* b) lacks ACL (set via logind or otherwise), thus
* any open() fill fail.
*
* As such, save the state of original other rw permissions
* and toggle them on.
*/
/* Note: we use a fixture to ensure the permissions are
* restored on skip or failure.
*/
igt_fixture {
num = tweak_perm(saved_perm, ARRAY_SIZE(saved_perm),
true);
}
igt_describe("Ensure first normal user can Set/DropMaster");
igt_subtest("master-drop-set-user") {
igt_fork(child, 1) {
igt_drop_root();
check_drop_set();
}
igt_waitchildren();
}
/* Restore the original permissions */
igt_fixture {
tweak_perm(saved_perm, num, false);
}
}
igt_describe("Check the Set/DropMaster behaviour on shared fd");
igt_subtest("master-drop-set-shared-fd") {
int master;
master = __drm_open_driver(DRIVER_ANY);
igt_require(master >= 0);
igt_assert_eq(is_master(master), true);
igt_fork(child, 1) {
igt_drop_root();
/* Dropping root privileges should not alter the
* master capability of the fd */
igt_assert_eq(is_master(master), true);
/* Even though we've got the master capable fd, we're
* a different process (kernel struct pid *) than the
* one which opened the device node.
*
* This ensures that existing workcases of separate
* (privileged) arbitrator still work. For example:
* - logind + X/Wayland compositor
* - weston-launch + weston
*/
igt_assert_eq(drmDropMaster(master), -1);
igt_assert_eq(errno, EACCES);
igt_assert_eq(drmSetMaster(master), -1);
igt_assert_eq(errno, EACCES);
close(master);
}
igt_waitchildren();
close(master);
}
}
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