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Commit a3f6c594 authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
Browse files

selftests: cgroup: Test open-time credential usage for migration checks 



commit 613e040e4dc285367bff0f8f75ea59839bc10947 upstream.

When a task is writing to an fd opened by a different task, the perm check
should use the credentials of the latter task. Add a test for it.

Tested-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
[OP: backport to v5.4: adjust context]
Signed-off-by: default avatarOvidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 48848242

tools/testing/selftests/cgroup/test_core.c

+68 −0
Original line number Diff line number Diff line
@@ -354,6 +354,73 @@ static int test_cgcore_internal_process_constraint(const char *root) 
	return ret;

}



/*

 * cgroup migration permission check should be performed based on the

 * credentials at the time of open instead of write.

 */

static int test_cgcore_lesser_euid_open(const char *root)

{

	const uid_t test_euid = 65534;	/* usually nobody, any !root is fine */

	int ret = KSFT_FAIL;

	char *cg_test_a = NULL, *cg_test_b = NULL;

	char *cg_test_a_procs = NULL, *cg_test_b_procs = NULL;

	int cg_test_b_procs_fd = -1;

	uid_t saved_uid;



	cg_test_a = cg_name(root, "cg_test_a");

	cg_test_b = cg_name(root, "cg_test_b");



	if (!cg_test_a || !cg_test_b)

		goto cleanup;



	cg_test_a_procs = cg_name(cg_test_a, "cgroup.procs");

	cg_test_b_procs = cg_name(cg_test_b, "cgroup.procs");



	if (!cg_test_a_procs || !cg_test_b_procs)

		goto cleanup;



	if (cg_create(cg_test_a) || cg_create(cg_test_b))

		goto cleanup;



	if (cg_enter_current(cg_test_a))

		goto cleanup;



	if (chown(cg_test_a_procs, test_euid, -1) ||

	    chown(cg_test_b_procs, test_euid, -1))

		goto cleanup;



	saved_uid = geteuid();

	if (seteuid(test_euid))

		goto cleanup;



	cg_test_b_procs_fd = open(cg_test_b_procs, O_RDWR);



	if (seteuid(saved_uid))

		goto cleanup;



	if (cg_test_b_procs_fd < 0)

		goto cleanup;



	if (write(cg_test_b_procs_fd, "0", 1) >= 0 || errno != EACCES)

		goto cleanup;



	ret = KSFT_PASS;



cleanup:

	cg_enter_current(root);

	if (cg_test_b_procs_fd >= 0)

		close(cg_test_b_procs_fd);

	if (cg_test_b)

		cg_destroy(cg_test_b);

	if (cg_test_a)

		cg_destroy(cg_test_a);

	free(cg_test_b_procs);

	free(cg_test_a_procs);

	free(cg_test_b);

	free(cg_test_a);

	return ret;

}



#define T(x) { x, #x }

struct corecg_test {

	int (*fn)(const char *root);
@@ -366,6 +433,7 @@ struct corecg_test { 
	T(test_cgcore_parent_becomes_threaded),

	T(test_cgcore_invalid_domain),

	T(test_cgcore_populated),

	T(test_cgcore_lesser_euid_open),

};

#undef T