[Tarantool-patches] [PATCH luajit v2] Fix command-line argv handling.

[Maxim Kokryashkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

From: Mike Pall <mike>

(cherry-picked from commit 9ebebc9b588dc1516c988b46d829445f505fdc1f)

Before the patch, there was a situation where `luaL_newstate`
could fail in main and the `argv[0]` could be used as a progname
in `l_message`. However, `argv[0]` is not guaranteed to be
non-NULL, so the segmentation fault could occur. This patch fixes
the issue by using the predefined name in that case. Moreover, it
refactors the `l_message`, so now there is no need to pass
`pname` everywhere.

The patch is tested with the help of the mocking of
`luaL_newstate` by providing an error-injected implementation
of it and preloading it. For preload to work, the LuaJIT must
be built with dynamic build mode enabled. The corresponding
flavor is added to the CI.

The tarantool-c-tests target cannot be linked with the LuaJIT
library when it is built as shared. The test suite is disabled
for the dynamic build mode.

Since the Linux kernel 5.18-rc1 release, `argv` is forced to a
single empty string if it is empty [1], so the issue is not
reproducible on new kernels.

[1]: https://lore.kernel.org/all/20220201000947.2453721-1-keescook@chromium.org/

Part of tarantool/tarantool#9924
---
Branch: https://github.com/tarantool/luajit/tree/fckxorg/fix-argv-handling

Changes in v2:
- Fixed comments as per review by Sergey Kaplun

 .github/workflows/exotic-builds-testing.yml   |  4 +-
 src/luajit.c                                  | 24 +++----
 test/tarantool-c-tests/CMakeLists.txt         |  8 +++
 test/tarantool-tests/CMakeLists.txt           |  9 +++
 .../fix-argv-handling.test.lua                | 25 +++++++
 .../fix-argv-handling/CMakeLists.txt          |  2 +
 .../fix-argv-handling/execlib.c               | 68 +++++++++++++++++++
 .../fix-argv-handling/mynewstate.c            |  9 +++
 8 files changed, 136 insertions(+), 13 deletions(-)
 create mode 100644 test/tarantool-tests/fix-argv-handling.test.lua
 create mode 100644 test/tarantool-tests/fix-argv-handling/CMakeLists.txt
 create mode 100644 test/tarantool-tests/fix-argv-handling/execlib.c
 create mode 100644 test/tarantool-tests/fix-argv-handling/mynewstate.c

diff --git a/.github/workflows/exotic-builds-testing.yml b/.github/workflows/exotic-builds-testing.yml
index 859603bd..ae54de2e 100644
--- a/.github/workflows/exotic-builds-testing.yml
+++ b/.github/workflows/exotic-builds-testing.yml
@@ -34,7 +34,7 @@ jobs:
         BUILDTYPE: [Debug, Release]
         ARCH: [ARM64, x86_64]
         GC64: [ON, OFF]
-        FLAVOR: [checkhook, dualnum, gdbjit, nojit, nounwind]
+        FLAVOR: [checkhook, dualnum, dynamic_build, gdbjit, nojit, nounwind]
         include:
           - BUILDTYPE: Debug
             CMAKEFLAGS: -DCMAKE_BUILD_TYPE=Debug -DLUA_USE_ASSERT=ON -DLUA_USE_APICHECK=ON
@@ -42,6 +42,8 @@ jobs:
             CMAKEFLAGS: -DCMAKE_BUILD_TYPE=RelWithDebInfo
           - FLAVOR: dualnum
             FLAVORFLAGS: -DLUAJIT_NUMMODE=2
+          - FLAVOR: dynamic_build
+            FLAVORFLAGS: -DBUILDMODE=dynamic
           - FLAVOR: checkhook
             FLAVORFLAGS: -DLUAJIT_ENABLE_CHECKHOOK=ON
           - FLAVOR: nojit
diff --git a/src/luajit.c b/src/luajit.c
index b63c92d1..dc142684 100644
--- a/src/luajit.c
+++ b/src/luajit.c
@@ -39,6 +39,7 @@

 static lua_State *globalL = NULL;
 static const char *progname = LUA_PROGNAME;
+static char *empty_argv[2] = { NULL, NULL };

 #if !LJ_TARGET_CONSOLE
 static void lstop(lua_State *L, lua_Debug *ar)
@@ -90,9 +91,9 @@ static void print_tools_usage(void)
   fflush(stderr);
 }

-static void l_message(const char *pname, const char *msg)
+static void l_message(const char *msg)
 {
-  if (pname) { fputs(pname, stderr); fputc(':', stderr); fputc(' ', stderr); }
+  if (progname) { fputs(progname, stderr); fputc(':', stderr); fputc(' ', stderr); }
   fputs(msg, stderr); fputc('\n', stderr);
   fflush(stderr);
 }
@@ -102,7 +103,7 @@ static int report(lua_State *L, int status)
   if (status && !lua_isnil(L, -1)) {
     const char *msg = lua_tostring(L, -1);
     if (msg == NULL) msg = "(error object is not a string)";
-    l_message(progname, msg);
+    l_message(msg);
     lua_pop(L, 1);
   }
   return status;
@@ -267,9 +268,8 @@ static void dotty(lua_State *L)
       lua_getglobal(L, "print");
       lua_insert(L, 1);
       if (lua_pcall(L, lua_gettop(L)-1, 0, 0) != 0)
-	l_message(progname,
-	  lua_pushfstring(L, "error calling " LUA_QL("print") " (%s)",
-			      lua_tostring(L, -1)));
+	l_message(lua_pushfstring(L, "error calling " LUA_QL("print") " (%s)",
+				  lua_tostring(L, -1)));
     }
   }
   lua_settop(L, 0);  /* clear stack */
@@ -321,8 +321,7 @@ static int loadjitmodule(lua_State *L)
   lua_getfield(L, -1, "start");
   if (lua_isnil(L, -1)) {
   nomodule:
-    l_message(progname,
-	      "unknown luaJIT command or jit.* modules not installed");
+    l_message("unknown luaJIT command or jit.* modules not installed");
     return 1;
   }
   lua_remove(L, -2);  /* Drop module table. */
@@ -382,7 +381,7 @@ static int runtoolcmd(lua_State *L, const char *tool_name)
     if (msg) {
       if (!strncmp(msg, "module ", 7))
 	msg = "unknown luaJIT command or tools not installed";
-      l_message(progname, msg);
+      l_message(msg);
     }
     return 1;
   }
@@ -566,7 +565,6 @@ static int pmain(lua_State *L)
   int argn;
   int flags = 0;
   globalL = L;
-  if (argv[0] && argv[0][0]) progname = argv[0];

   LUAJIT_VERSION_SYM();  /* Linker-enforced version check. */

@@ -622,9 +620,11 @@ static int pmain(lua_State *L)
 int main(int argc, char **argv)
 {
   int status;
-  lua_State *L = lua_open();
+  lua_State *L;
+  if (!argv[0]) argv = empty_argv; else if (argv[0][0]) progname = argv[0];
+  L = lua_open();  /* create state */
   if (L == NULL) {
-    l_message(argv[0], "cannot create state: not enough memory");
+    l_message("cannot create state: not enough memory");
     return EXIT_FAILURE;
   }
   smain.argc = argc;
diff --git a/test/tarantool-c-tests/CMakeLists.txt b/test/tarantool-c-tests/CMakeLists.txt
index 30d174bb..7ae440e2 100644
--- a/test/tarantool-c-tests/CMakeLists.txt
+++ b/test/tarantool-c-tests/CMakeLists.txt
@@ -36,6 +36,14 @@ add_test_suite_target(tarantool-c-tests
   DEPENDS libluajit libtest tarantool-c-tests-build
 )

+# XXX: The tarantool-c-tests target cannot be linked with the LuaJIT
+# library when it is built as shared. The test suite is disabled for
+# the dynamic build mode.
+if(BUILDMODE STREQUAL "dynamic")
+  message("Dynamic build mode, tarantool-c-tests suite is empty")
+  return()
+endif()
+
 set(CTEST_SRC_SUFFIX ".test.c")
 file(GLOB tests "${CMAKE_CURRENT_SOURCE_DIR}/*${CTEST_SRC_SUFFIX}")
 foreach(test_source ${tests})
diff --git a/test/tarantool-tests/CMakeLists.txt b/test/tarantool-tests/CMakeLists.txt
index 56660932..05deb534 100644
--- a/test/tarantool-tests/CMakeLists.txt
+++ b/test/tarantool-tests/CMakeLists.txt
@@ -40,6 +40,10 @@ add_subdirectory(lj-flush-on-trace)
 add_subdirectory(lj-1004-oom-error-frame)
 add_subdirectory(lj-1066-fix-cur_L-after-coroutine-resume)

+if(BUILDMODE STREQUAL "dynamic")
+  add_subdirectory(fix-argv-handling)
+endif()
+
 # The part of the memory profiler toolchain is located in tools
 # directory, jit, profiler, and bytecode toolchains are located
 # in src/ directory, jit/vmdef.lua is autogenerated file also
@@ -123,6 +127,11 @@ add_test_suite_target(tarantool-tests
 file(GLOB_RECURSE tests ${CMAKE_CURRENT_SOURCE_DIR} "*${LUA_TEST_SUFFIX}")
 foreach(test_path ${tests})
   get_filename_component(test_name ${test_path} NAME)
+
+  if(test_name STREQUAL "fix-argv-handling.test.lua" AND NOT BUILDMODE STREQUAL "dynamic")
+    continue()
+  endif()
+
   set(test_title "test/${TEST_SUITE_NAME}/${test_name}")
   add_test(NAME ${test_title}
     COMMAND ${LUAJIT_TEST_COMMAND} ${test_path}
diff --git a/test/tarantool-tests/fix-argv-handling.test.lua b/test/tarantool-tests/fix-argv-handling.test.lua
new file mode 100644
index 00000000..57e5f169
--- /dev/null
+++ b/test/tarantool-tests/fix-argv-handling.test.lua
@@ -0,0 +1,25 @@
+local tap = require('tap')
+local test = tap.test('fix-argv-handling'):skipcond({
+  ['DYLD_INSERT_LIBRARIES does not work on macOS'] = jit.os == 'OSX',
+})
+
+test:plan(1)
+
+-- XXX: Since the Linux kernel 5.18-rc1 release, `argv` is
+-- forced to a single empty string if it is empty [1], so
+-- the issue is not reproducible on new kernels.
+--
+-- [1]: https://lore.kernel.org/all/20220201000947.2453721-1-keescook@chromium.org/
+
+local utils = require('utils')
+local execlib = require('execlib')
+local cmd = utils.exec.luabin(arg)
+
+-- Start the LuaJIT with an empty argv array and mocked
+-- `luaL_newstate`.
+local output = execlib.empty_argv_exec(cmd)
+
+-- Without the patch, the test fails with a segmentation fault instead of
+-- returning an error.
+test:like(output, 'cannot create state', 'correct argv handling')
+test:done(true)
diff --git a/test/tarantool-tests/fix-argv-handling/CMakeLists.txt b/test/tarantool-tests/fix-argv-handling/CMakeLists.txt
new file mode 100644
index 00000000..c37bded7
--- /dev/null
+++ b/test/tarantool-tests/fix-argv-handling/CMakeLists.txt
@@ -0,0 +1,2 @@
+BuildTestCLib(mynewstate mynewstate.c)
+BuildTestCLib(execlib execlib.c)
diff --git a/test/tarantool-tests/fix-argv-handling/execlib.c b/test/tarantool-tests/fix-argv-handling/execlib.c
new file mode 100644
index 00000000..ef8217d4
--- /dev/null
+++ b/test/tarantool-tests/fix-argv-handling/execlib.c
@@ -0,0 +1,68 @@
+#include "lua.h"
+#include "lauxlib.h"
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+/* 1Kb should be enough. */
+#define BUF_SIZE 1024
+#define CHECKED(call) \
+do { \
+	if ((call) == -1) { \
+		perror(#call); \
+		exit(1); \
+	} \
+} while(0)
+
+static int empty_argv_exec(struct lua_State *L)
+{
+	const char *path = luaL_checkstring(L, -1);
+	int pipefds[2] = {};
+	char *const  argv[] = {NULL};
+	char buf[BUF_SIZE];
+
+	CHECKED(pipe2(pipefds, O_CLOEXEC));
+
+	pid_t pid = fork();
+	CHECKED(pid);
+
+	if (pid == 0) {
+		/*
+		 * Mock the `luaL_newstate` with
+		 * an error-injected version.
+		 */
+		setenv("LD_PRELOAD", "mynewstate.so", 1);
+		CHECKED(dup2(pipefds[1], 1));
+		CHECKED(dup2(pipefds[1], 2));
+		/*
+		 * Pipes are closed on the exec
+		 * call because of the O_CLOEXEC flag.
+		 */
+		CHECKED(execvp(path, argv));
+	}
+
+	close(pipefds[1]);
+	CHECKED(waitpid(pid, NULL, 0));
+
+
+	CHECKED(read(pipefds[0], buf, BUF_SIZE));
+	close(pipefds[0]);
+
+	lua_pushstring(L, buf);
+	return 1;
+}
+
+static const struct luaL_Reg execlib[] = {
+	{"empty_argv_exec", empty_argv_exec},
+	{NULL, NULL}
+};
+
+LUA_API int luaopen_execlib(lua_State *L)
+{
+	luaL_register(L, "execlib", execlib);
+	return 1;
+}
diff --git a/test/tarantool-tests/fix-argv-handling/mynewstate.c b/test/tarantool-tests/fix-argv-handling/mynewstate.c
new file mode 100644
index 00000000..cf4a67e7
--- /dev/null
+++ b/test/tarantool-tests/fix-argv-handling/mynewstate.c
@@ -0,0 +1,9 @@
+#include <stddef.h>
+
+struct lua_State;
+
+/* Error-injected mock. */
+struct lua_State *luaL_newstate(void)
+{
+	return NULL;
+}
--
2.44.0