Fix embedded bytecode loader.

(cherry-picked from commit 8203399)

The original problem is specific to x32 and is as follows: when a chunk
with a bytecode library is loaded into memory, and the address is higher
than 0x80000100, the `LexState->pe`, that contains an address of the end
of the bytecode chunk in the memory, will wrap around and become smaller
than the address in `LexState->p`, that contains an address of the
beginning of bytecode chunk in the memory. In `bcread_fill()` called by
`bcread_want()`, `memcpy()` is called with a very large size and causes
the bus error on x86 and the segmentation fault on ARM Android.

The problem cannot be reproduced on platforms supported by Tarantool
(ARM64, x86_64), so test doesn't reproduce a problem without a patch and
tests the patch partially.

Sergey Bronnikov:
* added the description and the test

Part of tarantool/tarantool#8825

src/lib_package.c

@@ -260,7 +260,7 @@ static int ll_loadfunc(lua_State *L, const char *path, const char *name, int r)
       const char *bcdata = ll_bcsym(*reg, mksymname(L, name, SYMPREFIX_BC));
       lua_pop(L, 1);
       if (bcdata) {
-	if (luaL_loadbuffer(L, bcdata, LJ_MAX_BUF, name) != 0)
+	if (luaL_loadbuffer(L, bcdata, ~(size_t)0, name) != 0)
 	  return PACKAGE_ERR_LOAD;
 	return 0;
       }
@@ -431,7 +431,7 @@ static int lj_cf_package_loader_preload(lua_State *L)
   if (lua_isnil(L, -1)) {  /* Not found? */
     const char *bcname = mksymname(L, name, SYMPREFIX_BC);
     const char *bcdata = ll_bcsym(NULL, bcname);
-    if (bcdata == NULL || luaL_loadbuffer(L, bcdata, LJ_MAX_BUF, name) != 0)
+    if (bcdata == NULL || luaL_loadbuffer(L, bcdata, ~(size_t)0, name) != 0)
       lua_pushfstring(L, "\n\tno field package.preload['%s']", name);
   }
   return 1;

src/lj_bcread.c

@@ -79,6 +79,7 @@ static LJ_NOINLINE void bcread_fill(LexState *ls, MSize len, int need)
       ls->c = -1;  /* Only bad if we get called again. */
       break;
     }
+    if (sz >= LJ_MAX_BUF - n) lj_err_mem(ls->L);
     if (n) {  /* Append to buffer. */
       n += (MSize)sz;
       p = lj_buf_need(&ls->sb, n < len ? len : n);
@@ -90,20 +91,20 @@ static LJ_NOINLINE void bcread_fill(LexState *ls, MSize len, int need)
       ls->p = buf;
       ls->pe = buf + sz;
     }
-  } while (ls->p + len > ls->pe);
+  } while ((MSize)(ls->pe - ls->p) < len);
 }
 
 /* Need a certain number of bytes. */
 static LJ_AINLINE void bcread_need(LexState *ls, MSize len)
 {
-  if (LJ_UNLIKELY(ls->p + len > ls->pe))
+  if (LJ_UNLIKELY((MSize)(ls->pe - ls->p) < len))
     bcread_fill(ls, len, 1);
 }
 
 /* Want to read up to a certain number of bytes, but may need less. */
 static LJ_AINLINE void bcread_want(LexState *ls, MSize len)
 {
-  if (LJ_UNLIKELY(ls->p + len > ls->pe))
+  if (LJ_UNLIKELY((MSize)(ls->pe - ls->p) < len))
     bcread_fill(ls, len, 0);
 }
 
@@ -463,8 +464,7 @@ GCproto *lj_bcread(LexState *ls)
     setprotoV(L, L->top, pt);
     incr_top(L);
   }
-  if ((int32_t)(2*(uint32_t)(ls->pe - ls->p)) > 0 ||
-      L->top-1 != bcread_oldtop(L, ls))
+  if ((ls->pe != ls->p && !ls->endmark) || L->top-1 != bcread_oldtop(L, ls))
     bcread_error(ls, LJ_ERR_BCBAD);
   /* Pop off last prototype. */
   L->top--;

src/lj_lex.c

@@ -48,6 +48,11 @@ static LJ_NOINLINE LexChar lex_more(LexState *ls)
   size_t sz;
   const char *p = ls->rfunc(ls->L, ls->rdata, &sz);
   if (p == NULL || sz == 0) return LEX_EOF;
+  if (sz >= LJ_MAX_BUF) {
+    if (sz != ~(size_t)0) lj_err_mem(ls->L);
+    sz = ~(uintptr_t)0 - (uintptr_t)p;
+    ls->endmark = 1;
+  }
   ls->pe = p + sz;
   ls->p = p + 1;
   return (LexChar)(uint8_t)p[0];
@@ -408,6 +413,7 @@ int lj_lex_setup(lua_State *L, LexState *ls)
   ls->lookahead = TK_eof;  /* No look-ahead token. */
   ls->linenumber = 1;
   ls->lastline = 1;
+  ls->endmark = 0;
   lex_next(ls);  /* Read-ahead first char. */
   if (ls->c == 0xef && ls->p + 2 <= ls->pe && (uint8_t)ls->p[0] == 0xbb &&
       (uint8_t)ls->p[1] == 0xbf) {  /* Skip UTF-8 BOM (if buffered). */

src/lj_lex.h

@@ -73,6 +73,7 @@ typedef struct LexState {
   BCInsLine *bcstack;	/* Stack for bytecode instructions/line numbers. */
   MSize sizebcstack;	/* Size of bytecode stack. */
   uint32_t level;	/* Syntactical nesting level. */
+  int endmark;		/* Trust bytecode end marker, even if not at EOF. */
 } LexState;
 
 LJ_FUNC int lj_lex_setup(lua_State *L, LexState *ls);

test/tarantool-tests/CMakeLists.txt

@@ -63,6 +63,7 @@ add_subdirectory(gh-5813-resolving-of-c-symbols/stripped)
 add_subdirectory(gh-6098-fix-side-exit-patching-on-arm64)
 add_subdirectory(gh-6189-cur_L)
 add_subdirectory(lj-416-xor-before-jcc)
+add_subdirectory(lj-549-bytecode-loader)
 add_subdirectory(lj-601-fix-gc-finderrfunc)
 add_subdirectory(lj-727-lightuserdata-itern)
 add_subdirectory(lj-802-panic-at-mcode-protfail)

test/tarantool-tests/lj-549-bytecode-loader.test.lua

@@ -0,0 +1,27 @@
+local tap = require('tap')
+local test = tap.test('lj-549-bytecode-loader')
+
+test:plan(2)
+
+-- Test creates a shared library with LuaJIT bytecode,
+-- loads shared library as a Lua module and checks,
+-- that no crashes eliminated.
+--
+-- Manual steps for reproducing are the following:
+--
+-- $ make HOST_CC='gcc -m32' TARGET_CFLAGS='-m32' \
+--                           TARGET_LDFLAGS='-m32' \
+--                           TARGET_SHLDFLAGS='-m32' \
+--                           -f Makefile.original
+-- $ echo 'print("test")' > a.lua
+-- $ LUA_PATH="src/?.lua;;" luajit -b a.lua a.c
+-- $ gcc -m32 -fPIC -shared a.c -o a.so
+-- $ luajit -e "require('a')"
+-- Program received signal SIGBUS, Bus error
+
+local module_name = 'script'
+local ok, module = pcall(require, module_name)
+test:is(ok, true, 'bytecode loader works')
+test:is(module.msg, 'Lango team', 'message is ok')
+
+test:done(true)

test/tarantool-tests/lj-549-bytecode-loader/CMakeLists.txt

@@ -0,0 +1,20 @@
+set(LIB_NAME "script")
+set(LUA_FILE ${CMAKE_CURRENT_SOURCE_DIR}/${LIB_NAME}.lua)
+set(C_FILE ${LIB_NAME}.c)
+
+make_lua_path(LUA_PATH
+  PATHS
+    ${PROJECT_SOURCE_DIR}/src/?.lua
+    ${PROJECT_SOURCE_DIR}/src/jit/?.lua
+)
+
+add_custom_target(export_bc
+  COMMAND ${CMAKE_COMMAND} -E env LUA_PATH=${LUA_PATH} ${LUAJIT_BINARY} -b ${LUA_FILE} ${C_FILE}
+  DEPENDS luajit-main ${LUA_FILE}
+  BYPRODUCTS ${C_FILE}
+  COMMENT "Exporting bytecode to a C file"
+  VERBATIM
+)
+
+BuildTestCLib(${LIB_NAME} ${C_FILE})
+add_dependencies(${LIB_NAME} export_bc)

test/tarantool-tests/lj-549-bytecode-loader/script.lua

@@ -0,0 +1,3 @@
+return {
+  msg = 'Lango team',
+}