From 2f9046fb059e94fe254c9a4ff5bcd52182069e44 Mon Sep 17 00:00:00 2001 From: Stefan Liebler Date: Wed, 18 Sep 2019 12:40:00 +0200 Subject: Add UNSUPPORTED check in elf/tst-pldd. The testcase forks a child process and runs pldd with PID of this child. On systems where /proc/sys/kernel/yama/ptrace_scope differs from zero, pldd will fail with /usr/bin/pldd: cannot attach to process 3: Operation not permitted This patch checks if ptrace_scope exists, is zero "classic ptrace permissions" or one "restricted ptrace". If ptrace_scope exists and has a higher restriction, then the test is marked as UNSUPPORTED. The case "restricted ptrace" is handled by rearranging the processes involved during the test. Now we have the following process tree: -parent: do_test (performs output checks) --subprocess 1: pldd_process (becomes pldd via execve) ---subprocess 2: target_process (ptraced via pldd) ChangeLog: * elf/tst-pldd.c (do_test): Add UNSUPPORTED check. Rearrange subprocesses. (pldd_process): New function. * support/Makefile (libsupport-routines): Add support_ptrace. * support/xptrace.h: New file. * support/support_ptrace.c: Likewise. --- elf/tst-pldd.c | 70 ++++++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 51 insertions(+), 19 deletions(-) (limited to 'elf') diff --git a/elf/tst-pldd.c b/elf/tst-pldd.c index 3f97e27..afe43f9 100644 --- a/elf/tst-pldd.c +++ b/elf/tst-pldd.c @@ -30,6 +30,11 @@ #include #include #include +#include +#include +#include +#include +#include static void target_process (void *arg) @@ -37,6 +42,34 @@ target_process (void *arg) pause (); } +static void +pldd_process (void *arg) +{ + pid_t *target_pid_ptr = (pid_t *) arg; + + /* Create a copy of current test to check with pldd. As the + target_process is a child of this pldd_process, pldd is also able + to attach to target_process if YAMA is configured to 1 = + "restricted ptrace". */ + struct support_subprocess target = support_subprocess (target_process, NULL); + + /* Store the pid of target-process as do_test needs it in order to + e.g. terminate it at end of the test. */ + *target_pid_ptr = target.pid; + + /* Three digits per byte plus null terminator. */ + char pid[3 * sizeof (uint32_t) + 1]; + snprintf (pid, array_length (pid), "%d", target.pid); + + char *prog = xasprintf ("%s/pldd", support_bindir_prefix); + + /* Run pldd and use the pid of target_process as argument. */ + execve (prog, (char *const []) { (char *) prog, pid, NULL }, + (char *const []) { NULL }); + + FAIL_EXIT1 ("Returned from execve: errno=%d=%m\n", errno); +} + /* The test runs in a container because pldd does not support tracing a binary started by the loader iself (as with testrun.sh). */ @@ -52,25 +85,22 @@ in_str_list (const char *libname, const char *const strlist[]) static int do_test (void) { - /* Create a copy of current test to check with pldd. */ - struct support_subprocess target = support_subprocess (target_process, NULL); - - /* Run 'pldd' on test subprocess. */ - struct support_capture_subprocess pldd; + /* Check if our subprocess can be debugged with ptrace. */ { - /* Three digits per byte plus null terminator. */ - char pid[3 * sizeof (uint32_t) + 1]; - snprintf (pid, array_length (pid), "%d", target.pid); - - char *prog = xasprintf ("%s/pldd", support_bindir_prefix); - - pldd = support_capture_subprogram (prog, - (char *const []) { (char *) prog, pid, NULL }); + int ptrace_scope = support_ptrace_scope (); + if (ptrace_scope >= 2) + FAIL_UNSUPPORTED ("/proc/sys/kernel/yama/ptrace_scope >= 2"); + } - support_capture_subprocess_check (&pldd, "pldd", 0, sc_allow_stdout); + pid_t *target_pid_ptr = (pid_t *) xmmap (NULL, sizeof (pid_t), + PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1); - free (prog); - } + /* Run 'pldd' on test subprocess which will be created in pldd_process. + The pid of the subprocess will be written to target_pid_ptr. */ + struct support_capture_subprocess pldd; + pldd = support_capture_subprocess (pldd_process, target_pid_ptr); + support_capture_subprocess_check (&pldd, "pldd", 0, sc_allow_stdout); /* Check 'pldd' output. The test is expected to be linked against only loader and libc. */ @@ -85,7 +115,7 @@ do_test (void) /* First line is in the form of : */ TEST_COMPARE (fscanf (out, "%u: " STRINPUT (512), &pid, buffer), 2); - TEST_COMPARE (pid, target.pid); + TEST_COMPARE (pid, *target_pid_ptr); TEST_COMPARE (strcmp (basename (buffer), "tst-pldd"), 0); /* It expects only one loader and libc loaded by the program. */ @@ -93,7 +123,7 @@ do_test (void) while (fgets (buffer, array_length (buffer), out) != NULL) { /* Ignore vDSO. */ - if (buffer[0] != '/') + if (buffer[0] != '/') continue; /* Remove newline so baseline (buffer) can compare against the @@ -128,7 +158,9 @@ do_test (void) } support_capture_subprocess_free (&pldd); - support_process_terminate (&target); + if (kill (*target_pid_ptr, SIGKILL) != 0) + FAIL_EXIT1 ("Unable to kill target_process: errno=%d=%m\n", errno); + xmunmap (target_pid_ptr, sizeof (pid_t)); return 0; } -- cgit v1.1