[igt-dev] [PATCH i-g-t v2] ts/core_setmaster: new test for drop/set master semantics
Petri Latvala
petri.latvala at intel.com
Fri Feb 21 11:58:25 UTC 2020
On Wed, Feb 19, 2020 at 02:24:45PM +0000, Emil Velikov wrote:
> From: Emil Velikov <emil.velikov at collabora.com>
>
> This test adds three distinct subtests:
> - drop/set master as root
> - drop/set master as non-root
> - drop/set master for a shared fd
>
> Currently the second subtest will fail, with kernel patch to address
> that has been submitted.
>
> v2: Add to the autotools build
>
> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> ---
> tests/Makefile.sources | 1 +
> tests/core_setmaster.c | 182 +++++++++++++++++++++++++++++++++++++++++
> tests/meson.build | 1 +
> 3 files changed, 184 insertions(+)
> create mode 100644 tests/core_setmaster.c
>
> diff --git a/tests/Makefile.sources b/tests/Makefile.sources
> index b87d6333..5da36a91 100644
> --- a/tests/Makefile.sources
> +++ b/tests/Makefile.sources
> @@ -18,6 +18,7 @@ TESTS_progs = \
> core_getclient \
> core_getstats \
> core_getversion \
> + core_setmaster \
> core_setmaster_vs_auth \
> debugfs_test \
> dmabuf \
> diff --git a/tests/core_setmaster.c b/tests/core_setmaster.c
> new file mode 100644
> index 00000000..2447c077
> --- /dev/null
> +++ b/tests/core_setmaster.c
> @@ -0,0 +1,182 @@
> +/*
> + * 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 at 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);
> +
> + /* Double-check if open has failed */
> + igt_assert_neq(master, -1);
Just use drm_open_driver(). For sure you don't want to produce a
'FAIL' when running on a system without GPU drivers. 'SKIP' is correct
for that case.
Same goes for the other __drm_open_driver() call.
> +
> + /* 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];
> + }
> +
> + /* In the extremely unlikely case of this failing, there't not
> + * much we can do.
We can igt_require that it works though. chmod failing means we get a
false 'FAIL' from the test.
Restoring failure leaves the system to a state that is going to scare
people with the extra perms...
> + */
> + chmod(path, st.st_mode);
> + }
> + return i;
> +}
> +
> +
> +igt_main
> +{
> + igt_subtest("master-drop-set-root") {
> + check_drop_set();
> + }
> +
> +
> + igt_subtest("master-drop-set-user") {
> + 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 logind ACL, thus
> + * any open() fill fail.
> + *
> + * As such, save the state of original other rw permissions
> + * and toggle them on.
> + */
> + num = tweak_perm(saved_perm, ARRAY_SIZE(saved_perm), true);
> +
> + igt_fork(child, 1) {
> + igt_drop_root();
> + check_drop_set();
> + }
> + igt_waitchildren();
> +
> + /* Restore the orignal permissions */
> + tweak_perm(saved_perm, num, false);
If the test fails we never restore the permissions with this flow. I
suppose this would be the best (but still ugly) way to make that
happen:
igt_fixture {
tweak_perm(...)
}
igt_subtest("master-drop-set-user") {
...
}
igt_fixture {
tweak_perm(saved);
}
Wrapping all that in an igt_subtest_group not required but could be
used to communicate to human readers that this is the subtest these
two fixtures are for.
--
Petri Latvala
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