From: Tejun Heo tj@kernel.org
commit bf35a7879f1dfb0d050fe779168bcf25c7de66f5 upstream.
When a task is writing to an fd opened by a different task, the perm check should use the cgroup namespace 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, add wait.h and fcntl.h includes] 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 | 99 +++++++++++++++++++++++++++++ 1 file changed, 99 insertions(+)
--- a/tools/testing/selftests/cgroup/test_core.c +++ b/tools/testing/selftests/cgroup/test_core.c @@ -1,8 +1,13 @@ /* SPDX-License-Identifier: GPL-2.0 */
+#define _GNU_SOURCE #include <linux/limits.h> +#include <linux/sched.h> #include <sys/types.h> +#include <sys/wait.h> #include <unistd.h> +#include <fcntl.h> +#include <sched.h> #include <stdio.h> #include <errno.h>
@@ -421,6 +426,99 @@ cleanup: return ret; }
+struct lesser_ns_open_thread_arg { + const char *path; + int fd; + int err; +}; + +static int lesser_ns_open_thread_fn(void *arg) +{ + struct lesser_ns_open_thread_arg *targ = arg; + + targ->fd = open(targ->path, O_RDWR); + targ->err = errno; + return 0; +} + +/* + * cgroup migration permission check should be performed based on the cgroup + * namespace at the time of open instead of write. + */ +static int test_cgcore_lesser_ns_open(const char *root) +{ + static char stack[65536]; + 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; + struct lesser_ns_open_thread_arg targ = { .fd = -1 }; + pid_t pid; + int status; + + 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_b)) + goto cleanup; + + if (chown(cg_test_a_procs, test_euid, -1) || + chown(cg_test_b_procs, test_euid, -1)) + goto cleanup; + + targ.path = cg_test_b_procs; + pid = clone(lesser_ns_open_thread_fn, stack + sizeof(stack), + CLONE_NEWCGROUP | CLONE_FILES | CLONE_VM | SIGCHLD, + &targ); + if (pid < 0) + goto cleanup; + + if (waitpid(pid, &status, 0) < 0) + goto cleanup; + + if (!WIFEXITED(status)) + goto cleanup; + + cg_test_b_procs_fd = targ.fd; + if (cg_test_b_procs_fd < 0) + goto cleanup; + + if (cg_enter_current(cg_test_a)) + goto cleanup; + + if ((status = write(cg_test_b_procs_fd, "0", 1)) >= 0 || errno != ENOENT) + 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); @@ -434,6 +532,7 @@ struct corecg_test { T(test_cgcore_invalid_domain), T(test_cgcore_populated), T(test_cgcore_lesser_euid_open), + T(test_cgcore_lesser_ns_open), }; #undef T