From: Tejun Heo tj@kernel.org
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 --- tools/testing/selftests/cgroup/test_core.c | 68 +++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+)
--- a/tools/testing/selftests/cgroup/test_core.c +++ b/tools/testing/selftests/cgroup/test_core.c @@ -354,6 +354,73 @@ cleanup: 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