[PATCH 4/4] elf: Make glibc.rtld.enable_secure ignore alias environment variables

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

So 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.
---
 elf/dl-tunables.c                |  34 ++++++--
 elf/tst-tunables-enable_secure.c | 131 +++++++++++++++++++++++++++----
 scripts/gen-tunables.awk         |  64 ++++++++++-----
 3 files changed, 189 insertions(+), 40 deletions(-)

diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 63cf8c7ab5..c1a1d1a2e3 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -300,6 +300,10 @@ __tunables_init (char **envp)
   if (__libc_enable_secure)
     return;
 
+  /* The tunable with environment variable alias are placed at the start of
+     tunable array.  */
+  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 +315,43 @@ __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];
+	  const char *name = cur->env_alias;
 
-	  /* Skip over tunables that have either been set already or should be
-	     skipped.  */
-	  if (cur->initialized || cur->env_alias[0] == '\0')
+	  if (name[0] == '\0')
 	    continue;
 
-	  const char *name = cur->env_alias;
-
-	  /* We have a match.  Initialize and move on to the next line.  */
 	  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++)
+    {
+      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
diff --git a/elf/tst-tunables-enable_secure.c b/elf/tst-tunables-enable_secure.c
index f5db1c84e9..d4938a2e5c 100644
--- a/elf/tst-tunables-enable_secure.c
+++ b/elf/tst-tunables-enable_secure.c
@@ -17,6 +17,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <array_length.h>
+#define TUNABLES_INTERNAL 1
 #include <dl-tunables.h>
 #include <getopt.h>
 #include <intprops.h>
@@ -34,6 +35,8 @@ 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 +44,124 @@ 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_malloc_check,
-		    TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
-      TEST_COMPARE (tests[i].expected_enable_secure,
-		    TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t,
-		    NULL));
-    }
+    TEST_COMPARE (tests[i].expected_enable_secure,
+		  TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t,
+				     NULL));
+  TEST_COMPARE (tests[i].expected_malloc_check,
+		TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
   return 0;
 }
 
@@ -112,8 +200,23 @@ do_test (int argc, char *argv[])
 
       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);
diff --git a/scripts/gen-tunables.awk b/scripts/gen-tunables.awk
index 9f5336381e..9a18aa6861 100644
--- a/scripts/gen-tunables.awk
+++ b/scripts/gen-tunables.awk
@@ -14,6 +14,7 @@ BEGIN {
   top_ns=""
   max_name_len=0
   max_alias_len=0
+  num_env_alias=0
 }
 
 # Skip over blank lines and comments.
@@ -60,6 +61,8 @@ $1 == "}" {
     }
     if (!env_alias[top_ns,ns,tunable]) {
       env_alias[top_ns,ns,tunable] = "{0}"
+    } else {
+      num_env_alias = num_env_alias + 1
     }
     len = length(top_ns"."ns"."tunable)
     if (len > max_name_len)
@@ -125,6 +128,39 @@ $1 == "}" {
   }
 }
 
+function print_tunable_id_t (envfirst)
+{
+  for (tnm in types) {
+    split (tnm, indices, SUBSEP);
+    t = indices[1];
+    n = indices[2];
+    m = indices[3];
+    if ((envfirst && env_alias[t,n,m] == "{0}") \
+	|| (!envfirst && env_alias[t,n,m] != "{0}")) {
+      continue;
+    }
+    printf ("  TUNABLE_ENUM_NAME(%s, %s, %s),\n", t, n, m);
+  }
+}
+
+function print_tunable_entry (envfirst)
+{
+  for (tnm in types) {
+    split (tnm, indices, SUBSEP);
+    t = indices[1];
+    n = indices[2];
+    m = indices[3];
+    if ((envfirst && env_alias[t,n,m] == "{0}") \
+	|| (!envfirst && env_alias[t,n,m] != "{0}")) {
+      continue;
+    }
+    printf ("  {TUNABLE_NAME_S(%s, %s, %s)", t, n, m)
+    printf (", {TUNABLE_TYPE_%s, %s, %s}, {%s}, {%s}, false, %s},\n",
+	    types[t,n,m], minvals[t,n,m], maxvals[t,n,m], default_val[t,n,m],
+	    default_val[t,n,m], env_alias[t,n,m]);
+  }
+}
+
 END {
   if (ns != "") {
     print "Unterminated namespace.  Is a closing brace missing?"
@@ -138,35 +174,27 @@ END {
   print "#endif"
   print "#include <dl-procinfo.h>\n"
 
+  # asort (types)
+
   # Now, the enum names
   print "\ntypedef enum"
   print "{"
-  for (tnm in types) {
-    split (tnm, indices, SUBSEP);
-    t = indices[1];
-    n = indices[2];
-    m = indices[3];
-    printf ("  TUNABLE_ENUM_NAME(%s, %s, %s),\n", t, n, m);
-  }
+  # Make the tunable with environment variables aliases first, their index
+  # will be used in the tunable parsing.
+  print_tunable_id_t(1)
+  print_tunable_id_t(0)
   print "} tunable_id_t;\n"
 
   print "\n#ifdef TUNABLES_INTERNAL"
   # Internal definitions.
   print "# define TUNABLE_NAME_MAX " (max_name_len + 1)
   print "# define TUNABLE_ALIAS_MAX " (max_alias_len + 1)
+  print "# define TUNABLE_NUM_ENV_ALIAS " (num_env_alias)
   print "# include \"dl-tunable-types.h\""
   # Finally, the tunable list.
-  print "static tunable_t tunable_list[] attribute_relro = {"
-  for (tnm in types) {
-    split (tnm, indices, SUBSEP);
-    t = indices[1];
-    n = indices[2];
-    m = indices[3];
-    printf ("  {TUNABLE_NAME_S(%s, %s, %s)", t, n, m)
-    printf (", {TUNABLE_TYPE_%s, %s, %s}, {%s}, {%s}, false, %s},\n",
-	    types[t,n,m], minvals[t,n,m], maxvals[t,n,m], default_val[t,n,m],
-	    default_val[t,n,m], env_alias[t,n,m]);
-  }
+  print "static tunable_t tunable_list[] attribute_relro __attribute_used__ = {"
+  print_tunable_entry(1)
+  print_tunable_entry(0)
   print "};"
   print "#endif"
 }
-- 
2.43.0