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.

--- a/gdb/common/linux-ptrace.c
+++ b/gdb/common/linux-ptrace.c
@@ -26,6 +26,10 @@
 #include "linux-ptrace.h"
 #include "linux-procfs.h"
 
+#ifdef HAVE_SELINUX_SELINUX_H
+# include <selinux/selinux.h>
+#endif /* HAVE_SELINUX_SELINUX_H */
+
 /* Print all possible reasons we could fail to attach PID.  */
 
 void
@@ -41,4 +45,21 @@ linux_ptrace_attach_warnings (pid_t pid)
   if (linux_proc_pid_is_zombie (pid))
     warning (_("process %d is a zombie - the process has already terminated"),
 	     (int) pid);
+
+  linux_ptrace_create_warnings ();
+}
+
+/* Print all possible reasons we could fail to create a traced process.  */
+
+void
+linux_ptrace_create_warnings (void)
+{
+#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)
+    warning (_("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 */
 }
--- a/gdb/common/linux-ptrace.h
+++ b/gdb/common/linux-ptrace.h
@@ -66,5 +66,6 @@
 #endif
 
 extern void linux_ptrace_attach_warnings (pid_t pid);
+extern void linux_ptrace_create_warnings (void);
 
 #endif /* COMMON_LINUX_PTRACE_H */
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1748,6 +1748,10 @@ 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,
--- a/gdb/gdbserver/configure.ac
+++ b/gdb/gdbserver/configure.ac
@@ -411,6 +411,10 @@ 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)
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -550,6 +550,25 @@ add_lwp (ptid_t ptid)
   return lwp;
 }
 
+/* Execute PTRACE_TRACEME with error checking.  */
+
+static void
+linux_traceme (const char *program)
+{
+  int save_errno;
+
+  errno = 0;
+  if (ptrace (PTRACE_TRACEME, 0, NULL, NULL) == 0)
+    return;
+
+  save_errno = errno;
+  linux_ptrace_create_warnings ();
+  fprintf (stderr, _("Cannot trace created process %s: %s.\n"), 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. */
 
@@ -590,7 +609,7 @@ linux_create_inferior (char *program, char **allargs)
 
   if (pid == 0)
     {
-      ptrace (PTRACE_TRACEME, 0, 0, 0);
+      linux_traceme (program);
 
 #ifndef __ANDROID__ /* Bionic doesn't use SIGRTMIN the way glibc does.  */
       signal (__SIGRTMIN + 1, SIG_DFL);
@@ -4386,7 +4405,7 @@ linux_tracefork_grandchild (void *arg)
 static int
 linux_tracefork_child (void *arg)
 {
-  ptrace (PTRACE_TRACEME, 0, 0, 0);
+  linux_traceme ("PTRACE_O_TRACEFORK test");
   kill (getpid (), SIGSTOP);
 
 #if !(defined(__UCLIBC__) && defined(HAS_NOMMU))
--- a/gdb/inf-ptrace.c
+++ b/gdb/inf-ptrace.c
@@ -105,7 +105,15 @@ 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
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1570,6 +1570,7 @@ linux_nat_create_inferior (struct target_ops *ops,
 #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.  */
@@ -1594,7 +1595,10 @@ linux_nat_create_inferior (struct target_ops *ops,
   /* 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)
@@ -1606,6 +1610,12 @@ linux_nat_create_inferior (struct target_ops *ops,
 		 safe_strerror (errno));
     }
 #endif /* HAVE_PERSONALITY */
+
+  if (ex.reason < 0)
+    {
+      linux_ptrace_create_warnings ();
+      throw_exception (ex);
+    }
 }
 
 static void