elf: Make glibc.rtld.enable_secure ignore alias environment variables

Tunable with environment variables aliases are also ignored if
glibc.rtld.enable_secure is enabled.  The tunable parsing is also
optimized a bit, where the loop that checks each environment variable
only checks for the tunables with aliases instead of all tables.

Checked on aarch64-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

elf/dl-tunables.c

@@ -300,6 +300,9 @@ __tunables_init (char **envp)
   if (__libc_enable_secure)
     return;
 
+  enum { tunable_num_env_alias = array_length (tunable_env_alias_list) };
+  struct tunable_toset_t tunables_env_alias[tunable_num_env_alias] = { 0 };
+
   while ((envp = get_next_env (envp, &envname, &envval, &prev_envp)) != NULL)
     {
       /* The environment variable is allocated on the stack by the kernel, so
@@ -311,29 +314,44 @@ __tunables_init (char **envp)
 	  continue;
 	}
 
-      for (int i = 0; i < tunables_list_size; i++)
+      for (int i = 0; i < tunable_num_env_alias; i++)
 	{
-	  tunable_t *cur = &tunable_list[i];
+	  tunable_t *cur = &tunable_list[tunable_env_alias_list[i]];
-
-	  /* Skip over tunables that have either been set already or should be
-	     skipped.  */
-	  if (cur->initialized || cur->env_alias[0] == '\0')
-	    continue;
-
 	  const char *name = cur->env_alias;
 
-	  /* We have a match.  Initialize and move on to the next line.  */
+	  if (name[0] == '\0')
+	    continue;
+
 	  if (tunable_is_name (name, envname))
 	    {
 	      size_t envvallen = 0;
 	      /* The environment variable is always null-terminated.  */
 	      for (const char *p = envval; *p != '\0'; p++, envvallen++);
 
-	      tunable_initialize (cur, envval, envvallen);
+	      tunables_env_alias[i] =
+		(struct tunable_toset_t) { cur, envval, envvallen };
 	      break;
 	    }
 	}
     }
+
+  /* Check if glibc.rtld.enable_secure was set and skip over the environment
+     variables aliases.  */
+  if (__libc_enable_secure)
+    return;
+
+  for (int i = 0; i < tunable_num_env_alias; i++)
+    {
+      /* Skip over tunables that have either been set or already initialized.  */
+      if (tunables_env_alias[i].t == NULL
+	  || tunables_env_alias[i].t->initialized)
+	continue;
+
+      if (!tunable_initialize (tunables_env_alias[i].t,
+			       tunables_env_alias[i].value,
+			       tunables_env_alias[i].len))
+	parse_tunable_print_error (&tunables_env_alias[i]);
+    }
 }
 
 void

elf/tst-tunables-enable_secure.c

@@ -17,6 +17,10 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <array_length.h>
+/* The test uses the tunable_env_alias_list size, which is only exported for
+   ld.so.  This will result in a copy of tunable_list and
+   tunable_env_alias_list, which is ununsed by the test itself.  */
+#define TUNABLES_INTERNAL 1
 #include <dl-tunables.h>
 #include <getopt.h>
 #include <intprops.h>
@@ -34,6 +38,8 @@ static int restart;
 static const struct test_t
 {
   const char *env;
+  const char *extraenv;
+  bool check_multiple;
   int32_t expected_malloc_check;
   int32_t expected_enable_secure;
 } tests[] =
@@ -41,39 +47,124 @@ static const struct test_t
   /* Expected tunable format.  */
   /* Tunables should be ignored if enable_secure is set. */
   {
-    "glibc.malloc.check=2:glibc.rtld.enable_secure=1",
+    "GLIBC_TUNABLES=glibc.malloc.check=2:glibc.rtld.enable_secure=1",
+    NULL,
+    false,
     0,
     1,
   },
   /* Tunables should be ignored if enable_secure is set. */
   {
-    "glibc.rtld.enable_secure=1:glibc.malloc.check=2",
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=1:glibc.malloc.check=2",
+    NULL,
+    false,
     0,
     1,
   },
   /* Tunables should be set if enable_secure is unset. */
   {
-    "glibc.rtld.enable_secure=0:glibc.malloc.check=2",
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=0:glibc.malloc.check=2",
+    NULL,
+    false,
     2,
     0,
   },
+  /* Tunables should be ignored if enable_secure is set. */
+  {
+    "GLIBC_TUNABLES=glibc.malloc.check=2:glibc.rtld.enable_secure=1",
+    "MALLOC_CHECK_=2",
+    false,
+    0,
+    1,
+  },
+  /* Same as before, but with enviroment alias prior GLIBC_TUNABLES.  */
+  {
+    "MALLOC_CHECK_=2",
+    "GLIBC_TUNABLES=glibc.malloc.check=2:glibc.rtld.enable_secure=1",
+    false,
+    0,
+    1,
+  },
+  /* Tunables should be ignored if enable_secure is set. */
+  {
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=1:glibc.malloc.check=2",
+    "MALLOC_CHECK_=2",
+    false,
+    0,
+    1,
+  },
+  {
+    "MALLOC_CHECK_=2",
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=1:glibc.malloc.check=2",
+    false,
+    0,
+    1,
+  },
+  /* Tunables should be set if enable_secure is unset. */
+  {
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=0:glibc.malloc.check=2",
+    /* Tunable have precedence over the environment variable.  */
+    "MALLOC_CHECK_=1",
+    false,
+    2,
+    0,
+  },
+  {
+    "MALLOC_CHECK_=1",
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=0:glibc.malloc.check=2",
+    /* Tunable have precedence over the environment variable.  */
+    false,
+    2,
+    0,
+  },
+  /* Tunables should be set if enable_secure is unset. */
+  {
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=0",
+    /* Tunable have precedence over the environment variable.  */
+    "MALLOC_CHECK_=1",
+    false,
+    1,
+    0,
+  },
+  /* Tunables should be set if enable_secure is unset. */
+  {
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=0",
+    /* Tunable have precedence over the environment variable.  */
+    "MALLOC_CHECK_=1",
+    false,
+    1,
+    0,
+  },
+  /* Check with tunables environment variable alias set multiple times.  */
+  {
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=1:glibc.malloc.check=2",
+    "MALLOC_CHECK_=2",
+    true,
+    0,
+    1,
+  },
+  /* Tunables should be set if enable_secure is unset. */
+  {
+    "GLIBC_TUNABLES=glibc.rtld.enable_secure=0",
+    /* Tunable have precedence over the environment variable.  */
+    "MALLOC_CHECK_=1",
+    true,
+    1,
+    0,
+  },
 };
 
 static int
 handle_restart (int i)
 {
   if (tests[i].expected_enable_secure == 1)
-    {
+    TEST_COMPARE (1, __libc_enable_secure);
-      TEST_COMPARE (1, __libc_enable_secure);
-    }
   else
-    {
+    TEST_COMPARE (tests[i].expected_enable_secure,
-      TEST_COMPARE (tests[i].expected_malloc_check,
+		  TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t,
-		    TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
+				     NULL));
-      TEST_COMPARE (tests[i].expected_enable_secure,
+  TEST_COMPARE (tests[i].expected_malloc_check,
-		    TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t,
+		TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
-		    NULL));
-    }
   return 0;
 }
 
@@ -106,14 +197,31 @@ do_test (int argc, char *argv[])
     spargv[i] = NULL;
   }
 
+  enum { tunable_num_env_alias = array_length (tunable_env_alias_list) };
+
   for (int i = 0; i < array_length (tests); i++)
     {
       snprintf (nteststr, sizeof nteststr, "%d", i);
 
       printf ("[%d] Spawned test for %s\n", i, tests[i].env);
       setenv ("GLIBC_TUNABLES", tests[i].env, 1);
+
+      char *envp[2 + tunable_num_env_alias + 1] =
+      {
+	(char *) tests[i].env,
+	(char *) tests[i].extraenv,
+	NULL,
+      };
+      if (tests[i].check_multiple)
+	{
+	  int j;
+	  for (j=0; j < tunable_num_env_alias; j++)
+	    envp[j + 2] = (char *) tests[i].extraenv;
+	  envp[j + 2] = NULL;
+	}
+
       struct support_capture_subprocess result
-	= support_capture_subprogram (spargv[0], spargv, NULL);
+	= support_capture_subprogram (spargv[0], spargv, envp);
       support_capture_subprocess_check (&result, "tst-tunables-enable_secure",
 		                        0, sc_allow_stderr);
       support_capture_subprocess_free (&result);

scripts/gen-tunables.awk

@@ -156,7 +156,7 @@ END {
   print "# define TUNABLE_ALIAS_MAX " (max_alias_len + 1)
   print "# include \"dl-tunable-types.h\""
   # Finally, the tunable list.
-  print "static tunable_t tunable_list[] attribute_relro = {"
+  print "static tunable_t tunable_list[] attribute_relro __attribute_used__ = {"
   for (tnm in types) {
     split (tnm, indices, SUBSEP);
     t = indices[1];
@@ -168,5 +168,19 @@ END {
 	    default_val[t,n,m], env_alias[t,n,m]);
   }
   print "};"
+
+  # Map of tunable with environment variables aliases used during parsing.  */
+  print "\nstatic const tunable_id_t tunable_env_alias_list[] ="
+  printf "{\n"
+  for (tnm in types) {
+    split (tnm, indices, SUBSEP);
+    t = indices[1];
+    n = indices[2];
+    m = indices[3];
+    if (env_alias[t,n,m] != "{0}") {
+      printf ("  TUNABLE_ENUM_NAME(%s, %s, %s),\n", t, n, m);
+    }
+  }
+  printf "};\n"
   print "#endif"
 }