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

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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: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[OP: backport to v5.4: adjust context]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2022-04-14 11:44:49 +03:00 committed by Greg Kroah-Hartman
parent 48848242d3
commit a3f6c5949f
1 changed files with 68 additions and 0 deletions
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68
tools/testing/selftests/cgroup/test_core.c
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@ -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