commit 2f9046fb059e94fe254c9a4ff5bcd52182069e44
Author: Stefan Liebler <stli@linux.ibm.com>
Date: Wed Sep 18 12:40:00 2019 +0200
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.
Conflicts:
elf/tst-pldd.c
(Original backport uses spaces instead of tabs.)
diff --git a/elf/tst-pldd.c b/elf/tst-pldd.c
index e2de31282a131166..f381cb0fa7e6b93d 100644
--- a/elf/tst-pldd.c
+++ b/elf/tst-pldd.c
@@ -30,6 +30,11 @@
#include <support/capture_subprocess.h>
#include <support/check.h>
#include <support/support.h>
+#include <support/xptrace.h>
+#include <support/xunistd.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <signal.h>
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. */
@@ -85,15 +115,15 @@ do_test (void)
/* First line is in the form of <pid>: <full path of executable> */
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. */
bool interpreter_found = false, libc_found = false;
while (fgets (buffer, array_length (buffer), out) != NULL)
{
- /* Ignore vDSO. */
- if (buffer[0] != '/')
+ /* Ignore vDSO. */
+ 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;
}
diff --git a/support/Makefile b/support/Makefile
index 65b16299573af1ed..79d03bd6bfe02540 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -58,6 +58,7 @@ libsupport-routines = \
support_format_hostent \
support_format_netent \
support_isolate_in_subprocess \
+ support_ptrace \
support_openpty \
support_paths \
support_quote_blob \
diff --git a/support/support_ptrace.c b/support/support_ptrace.c
new file mode 100644
index 0000000000000000..616b08cff33022ef
--- /dev/null
+++ b/support/support_ptrace.c
@@ -0,0 +1,44 @@
+/* Support functions handling ptrace_scope.
+ Copyright (C) 2019 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <support/check.h>
+#include <support/xstdio.h>
+#include <support/xptrace.h>
+#include <sys/prctl.h>
+
+int
+support_ptrace_scope (void)
+{
+ int ptrace_scope = -1;
+
+#ifdef __linux__
+ /* YAMA may be not enabled. Otherwise it contains a value from 0 to 3:
+ - 0 classic ptrace permissions
+ - 1 restricted ptrace
+ - 2 admin-only attach
+ - 3 no attach */
+ FILE *f = fopen ("/proc/sys/kernel/yama/ptrace_scope", "r");
+ if (f != NULL)
+ {
+ TEST_COMPARE (fscanf (f, "%d", &ptrace_scope), 1);
+ xfclose (f);
+ }
+#endif
+
+ return ptrace_scope;
+}
diff --git a/support/xptrace.h b/support/xptrace.h
new file mode 100644
index 0000000000000000..7af892680578fffd
--- /dev/null
+++ b/support/xptrace.h
@@ -0,0 +1,32 @@
+/* Support functions handling ptrace_scope.
+ Copyright (C) 2019 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef SUPPORT_PTRACE_H
+#define SUPPORT_PTRACE_H
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Return the current YAMA mode set on the machine (0 to 3) or -1
+ if YAMA is not supported. */
+int support_ptrace_scope (void);
+
+__END_DECLS
+
+#endif