http://sourceware.org/ml/gdb-patches/2012-03/msg00171.html
Subject: [patch 3/3] attach-fail-reasons: SELinux deny_ptrace

Hi,

and here is the last bit for new SELinux 'deny_ptrace':
	https://bugzilla.redhat.com/show_bug.cgi?id=786878

As even PTRACE_TRACEME fails in such case it needs to install hook for even
that event.


Thanks,
Jan


gdb/
2012-03-06  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* common/linux-ptrace.c [HAVE_SELINUX_SELINUX_H]: include
	selinux/selinux.h.
	(linux_ptrace_attach_warnings): Call linux_ptrace_create_warnings.
	(linux_ptrace_create_warnings): New.
	* common/linux-ptrace.h (linux_ptrace_create_warnings): New declaration.
	* config.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Check selinux/selinux.h and the selinux library.
	* inf-ptrace.c (inf_ptrace_me): Check the ptrace result.
	* linux-nat.c (linux_nat_create_inferior): New variable ex.  Wrap
	to_create_inferior into TRY_CATCH, call linux_ptrace_create_warnings.

gdb/gdbserver/
	* config.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Check selinux/selinux.h and the selinux library.
	* linux-low.c (linux_traceme): New function.
	(linux_create_inferior, linux_tracefork_child): Call it instead of
	direct ptrace.

Index: gdb-7.5.50.20130215/gdb/common/linux-ptrace.c
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/common/linux-ptrace.c	2013-01-08 20:38:51.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/common/linux-ptrace.c	2013-02-15 22:38:05.782456279 +0100
@@ -29,6 +29,10 @@
 #include "gdb_assert.h"
 #include "gdb_wait.h"
 
+#ifdef HAVE_SELINUX_SELINUX_H
+# include <selinux/selinux.h>
+#endif /* HAVE_SELINUX_SELINUX_H */
+
 /* Find all possible reasons we could fail to attach PID and append these
    newline terminated reason strings to initialized BUFFER.  '\0' termination
    of BUFFER must be done by the caller.  */
@@ -48,6 +52,8 @@ linux_ptrace_attach_warnings (pid_t pid,
     buffer_xml_printf (buffer, _("warning: process %d is a zombie "
 				 "- the process has already terminated\n"),
 		       (int) pid);
+
+  linux_ptrace_create_warnings (buffer);
 }
 
 #if defined __i386__ || defined __x86_64__
@@ -243,3 +249,19 @@ linux_ptrace_init_warnings (void)
 
   linux_ptrace_test_ret_to_nx ();
 }
+
+/* Print all possible reasons we could fail to create a traced process.  */
+
+void
+linux_ptrace_create_warnings (struct buffer *buffer)
+{
+#ifdef HAVE_LIBSELINUX
+  /* -1 is returned for errors, 0 if it has no effect, 1 if PTRACE_ATTACH is
+     forbidden.  */
+  if (security_get_boolean_active ("deny_ptrace") == 1)
+    buffer_xml_printf (buffer,
+		       _("the SELinux boolean 'deny_ptrace' is enabled, "
+			 "you can disable this process attach protection by: "
+			 "(gdb) shell sudo setsebool deny_ptrace=0"));
+#endif /* HAVE_LIBSELINUX */
+}
Index: gdb-7.5.50.20130215/gdb/common/linux-ptrace.h
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/common/linux-ptrace.h	2013-01-01 07:32:54.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/common/linux-ptrace.h	2013-02-15 22:38:05.782456279 +0100
@@ -69,5 +69,6 @@ struct buffer;
 
 extern void linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer);
 extern void linux_ptrace_init_warnings (void);
+extern void linux_ptrace_create_warnings (struct buffer *buffer);
 
 #endif /* COMMON_LINUX_PTRACE_H */
Index: gdb-7.5.50.20130215/gdb/configure.ac
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/configure.ac	2013-02-15 22:37:57.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/configure.ac	2013-02-15 22:38:05.783456281 +0100
@@ -2068,6 +2068,10 @@ then
 	      [Define if you support the personality syscall.])
 fi
 
+dnl Check security_get_boolean_active availability.
+AC_CHECK_HEADERS(selinux/selinux.h)
+AC_CHECK_LIB(selinux, security_get_boolean_active)
+
 dnl Handle optional features that can be enabled.
 
 # Support for --with-sysroot is a copy of GDB_AC_WITH_DIR,
Index: gdb-7.5.50.20130215/gdb/gdbserver/configure.ac
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/gdbserver/configure.ac	2013-01-01 07:33:00.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/gdbserver/configure.ac	2013-02-15 22:38:05.783456281 +0100
@@ -451,6 +451,10 @@ if $want_ipa ; then
    fi
 fi
 
+dnl Check security_get_boolean_active availability.
+AC_CHECK_HEADERS(selinux/selinux.h)
+AC_CHECK_LIB(selinux, security_get_boolean_active)
+
 AC_SUBST(GDBSERVER_DEPFILES)
 AC_SUBST(GDBSERVER_LIBS)
 AC_SUBST(USE_THREAD_DB)
Index: gdb-7.5.50.20130215/gdb/gdbserver/linux-low.c
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/gdbserver/linux-low.c	2013-02-04 18:47:00.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/gdbserver/linux-low.c	2013-02-15 22:39:54.256591069 +0100
@@ -602,6 +602,29 @@ add_lwp (ptid_t ptid)
   return lwp;
 }
 
+/* Execute PTRACE_TRACEME with error checking.  */
+
+static void
+linux_traceme (const char *program)
+{
+  int save_errno;
+  struct buffer buffer;
+
+  errno = 0;
+  if (ptrace (PTRACE_TRACEME, 0,
+	      (PTRACE_ARG3_TYPE) 0, (PTRACE_ARG4_TYPE) 0) == 0)
+    return;
+
+  save_errno = errno;
+  buffer_init (&buffer);
+  linux_ptrace_create_warnings (&buffer);
+  buffer_grow_str0 (&buffer, "");
+  fprintf (stderr, _("%sCannot trace created process %s: %s.\n"),
+	   buffer_finish (&buffer), program, strerror (save_errno));
+  fflush (stderr);
+  _exit (0177);
+}
+
 /* Start an inferior process and returns its pid.
    ALLARGS is a vector of program-name and args. */
 
@@ -642,7 +665,7 @@ linux_create_inferior (char *program, ch
 
   if (pid == 0)
     {
-      ptrace (PTRACE_TRACEME, 0, (PTRACE_ARG3_TYPE) 0, (PTRACE_ARG4_TYPE) 0);
+      linux_traceme (program);
 
 #ifndef __ANDROID__ /* Bionic doesn't use SIGRTMIN the way glibc does.  */
       signal (__SIGRTMIN + 1, SIG_DFL);
@@ -4587,7 +4610,7 @@ linux_tracefork_grandchild (void *arg)
 static int
 linux_tracefork_child (void *arg)
 {
-  ptrace (PTRACE_TRACEME, 0, (PTRACE_ARG3_TYPE) 0, (PTRACE_ARG4_TYPE) 0);
+  linux_traceme ("PTRACE_O_TRACEFORK test");
   kill (getpid (), SIGSTOP);
 
 #if !(defined(__UCLIBC__) && defined(HAS_NOMMU))
Index: gdb-7.5.50.20130215/gdb/inf-ptrace.c
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/inf-ptrace.c	2013-01-01 07:32:45.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/inf-ptrace.c	2013-02-15 22:38:05.786456289 +0100
@@ -104,7 +104,15 @@ static void
 inf_ptrace_me (void)
 {
   /* "Trace me, Dr. Memory!"  */
+  errno = 0;
   ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3)0, 0);
+  if (errno != 0)
+    {
+      fprintf_unfiltered (gdb_stderr, _("Cannot create process: %s\n"),
+			  safe_strerror (errno));
+      gdb_flush (gdb_stderr);
+      _exit (0177);
+    }
 }
 
 /* Start a new inferior Unix child process.  EXEC_FILE is the file to
Index: gdb-7.5.50.20130215/gdb/linux-nat.c
===================================================================
--- gdb-7.5.50.20130215.orig/gdb/linux-nat.c	2013-02-15 22:34:44.000000000 +0100
+++ gdb-7.5.50.20130215/gdb/linux-nat.c	2013-02-15 22:38:05.787456291 +0100
@@ -1557,6 +1557,7 @@ linux_nat_create_inferior (struct target
 #ifdef HAVE_PERSONALITY
   int personality_orig = 0, personality_set = 0;
 #endif /* HAVE_PERSONALITY */
+  volatile struct gdb_exception ex;
 
   /* The fork_child mechanism is synchronous and calls target_wait, so
      we have to mask the async mode.  */
@@ -1581,7 +1582,10 @@ linux_nat_create_inferior (struct target
   /* Make sure we report all signals during startup.  */
   linux_nat_pass_signals (0, NULL);
 
-  linux_ops->to_create_inferior (ops, exec_file, allargs, env, from_tty);
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      linux_ops->to_create_inferior (ops, exec_file, allargs, env, from_tty);
+    }
 
 #ifdef HAVE_PERSONALITY
   if (personality_set)
@@ -1593,6 +1597,24 @@ linux_nat_create_inferior (struct target
 		 safe_strerror (errno));
     }
 #endif /* HAVE_PERSONALITY */
+
+  if (ex.reason < 0)
+    {
+      struct buffer buffer;
+      char *message, *buffer_s;
+
+      message = xstrdup (ex.message);
+      make_cleanup (xfree, message);
+
+      buffer_init (&buffer);
+      linux_ptrace_create_warnings (&buffer);
+
+      buffer_grow_str0 (&buffer, "");
+      buffer_s = buffer_finish (&buffer);
+      make_cleanup (xfree, buffer_s);
+
+      throw_error (ex.error, "%s%s", buffer_s, message);
+    }
 }
 
 static void