% grep -R 5.1.5 *
Makefile:R= 5.1.5
doc/contents.html:Last change: revised for Lua 5.1.5
doc/readme.html:This is the documentation included in the source distribution of Lua 5.1.5.
doc/manual.html:Last change: revised for Lua 5.1.5
etc/lua.pc:R= 5.1.5
src/lcode.c:** $Id: lcode.c,v 2.25.1.5 2011/01/31 14:53:16 roberto Exp $
src/lapi.c:** $Id: lapi.c,v 2.55.1.5 2008/07/04 18:41:18 roberto Exp $
src/lua.h:#define LUA_RELEASE	"Lua 5.1.5"

From 74d99057a5146755e737c479850f87fd0e3b6868 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 3 Nov 2021 15:04:18 -0300
Subject: [PATCH] Bug: C stack overflow with coroutines

'coroutine.resume' did not increment counter of C calls when
continuing execution after a protected error (that is,
while running 'precover').
---
 ldo.c             |  6 ++++--
 testes/cstack.lua | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/ldo.c b/ldo.c
index d0edc8b4f..66f890364 100644
--- a/ldo.c
+++ b/ldo.c
@@ -759,11 +759,10 @@ static void resume (lua_State *L, void *ud) {
   StkId firstArg = L->top - n;  /* first argument */
   CallInfo *ci = L->ci;
   if (L->status == LUA_OK)  /* starting a coroutine? */
-    ccall(L, firstArg - 1, LUA_MULTRET, 1);  /* just call its body */
+    ccall(L, firstArg - 1, LUA_MULTRET, 0);  /* just call its body */
   else {  /* resuming from previous yield */
     lua_assert(L->status == LUA_YIELD);
     L->status = LUA_OK;  /* mark that it is running (again) */
-    luaE_incCstack(L);  /* control the C stack */
     if (isLua(ci)) {  /* yielded inside a hook? */
       L->top = firstArg;  /* discard arguments */
       luaV_execute(L, ci);  /* just continue running Lua code */
@@ -814,6 +813,9 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
   else if (L->status != LUA_YIELD)  /* ended with errors? */
     return resume_error(L, "cannot resume dead coroutine", nargs);
   L->nCcalls = (from) ? getCcalls(from) : 0;
+  if (getCcalls(L) >= LUAI_MAXCCALLS)
+    return resume_error(L, "C stack overflow", nargs);
+  L->nCcalls++;
   luai_userstateresume(L, nargs);
   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
   status = luaD_rawrunprotected(L, resume, &nargs);
diff --git a/testes/cstack.lua b/testes/cstack.lua
index 213d15d47..ca76c8729 100644
--- a/testes/cstack.lua
+++ b/testes/cstack.lua
@@ -103,6 +103,20 @@ do
 end
 
 
+do    -- bug in 5.4.2
+  print("nesting coroutines running after recoverable errors")
+  local count = 0
+  local function foo()
+    count = count + 1
+    pcall(1)   -- create an error
+    -- running now inside 'precover' ("protected recover")
+    coroutine.wrap(foo)()   -- call another coroutine
+  end
+  checkerror("C stack overflow", foo)
+  print("final count: ", count)
+end
+
+
 if T then
   print("testing stack recovery")
   local N = 0      -- trace number of calls

static void resume (lua_State *L, void *ud) {
  StkId firstArg = cast(StkId, ud);
  CallInfo *ci = L->ci;
  if (L->status == 0) {  /* start coroutine? */
    lua_assert(ci == L->base_ci && firstArg > L->base);
    if (luaD_precall(L, firstArg - 1, LUA_MULTRET) != PCRLUA)
      return;
  }
  else {  /* resuming from previous yield */
    lua_assert(L->status == LUA_YIELD);
    L->status = 0;
    if (!f_isLua(ci)) {  /* `common' yield? */
      /* finish interrupted execution of `OP_CALL' */
      lua_assert(GET_OPCODE(*((ci-1)->savedpc - 1)) == OP_CALL ||
                 GET_OPCODE(*((ci-1)->savedpc - 1)) == OP_TAILCALL);
      if (luaD_poscall(L, firstArg))  /* complete it... */
        L->top = L->ci->top;  /* and correct top if not multiple results */
    }
    else  /* yielded inside a hook: just continue its execution */
      L->base = L->ci->base;
  }
  luaV_execute(L, cast_int(L->ci - L->base_ci));
}

/*
** Do the work for 'lua_resume' in protected mode. Most of the work
** depends on the status of the coroutine: initial state, suspended
** inside a hook, or regularly suspended (optionally with a continuation
** function), plus erroneous cases: non-suspended coroutine or dead
** coroutine.
*/
static void resume (lua_State *L, void *ud) {
  int n = *(cast(int*, ud));  /* number of arguments */
  StkId firstArg = L->top - n;  /* first argument */
  CallInfo *ci = L->ci;
  if (L->status == LUA_OK)  /* starting a coroutine? */
    ccall(L, firstArg - 1, LUA_MULTRET, 1);  /* just call its body */
  else {  /* resuming from previous yield */
    lua_assert(L->status == LUA_YIELD);
    L->status = LUA_OK;  /* mark that it is running (again) */
    luaE_incCstack(L);  /* control the C stack */
    if (isLua(ci)) {  /* yielded inside a hook? */
      L->top = firstArg;  /* discard arguments */
      luaV_execute(L, ci);  /* just continue running Lua code */
    }
    else {  /* 'common' yield */
      if (ci->u.c.k != NULL) {  /* does it have a continuation function? */
        lua_unlock(L);
        n = (*ci->u.c.k)(L, LUA_YIELD, ci->u.c.ctx); /* call continuation */
        lua_lock(L);
        api_checknelems(L, n);
      }
      luaD_poscall(L, ci, n);  /* finish 'luaD_call' */
    }
    unroll(L, NULL);  /* run continuation */
  }
}

local p = {}
function p.hello( frame )
	coroutine.wrap(p.hello)()
	return "Hello, World!"
end
return p

Lua error at line 7: attempt to index global 'coroutine' (a nil value).

Backtrace:

    (tail call): ?
    Module:Loop:7: in function "hello"
    console input:7: ?
    (tail call): ?
    [C]: in function "xpcall"
    MWServer.lua:99: in function "handleCall"
    MWServer.lua:313: in function "dispatch"
    MWServer.lua:52: in function "execute"
    mw_main.lua:7: in main chunk
    [C]: ?