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File luabugs4.patch of Package lua54 (Revision b37e5a09a1c9394b62f6ba2577116767)

Currently displaying revision b37e5a09a1c9394b62f6ba2577116767 , Show latest

From 42d40581dd919fb134c07027ca1ce0844c670daf Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 20 May 2022 13:14:33 -0300
Subject: [PATCH] Save stack space while handling errors

Because error handling (luaG_errormsg) uses slots from EXTRA_STACK,
and some errors can recur (e.g., string overflow while creating an
error message in 'luaG_runerror', or a C-stack overflow before calling
the message handler), the code should use stack slots with parsimony.

This commit fixes the bug "Lua-stack overflow when C stack overflows
while handling an error".
---
 ldebug.c | 5 ++++-
 lvm.c    | 6 ++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/ldebug.c b/ldebug.c
index a716d95e2..fa15eaf68 100644
--- a/src/ldebug.c
+++ b/src/ldebug.c
@@ -824,8 +824,11 @@ l_noret luaG_runerror (lua_State *L, const char *fmt, ...) {
   va_start(argp, fmt);
   msg = luaO_pushvfstring(L, fmt, argp);  /* format message */
   va_end(argp);
-  if (isLua(ci))  /* if Lua function, add source:line information */
+  if (isLua(ci)) {  /* if Lua function, add source:line information */
     luaG_addinfo(L, msg, ci_func(ci)->p->source, getcurrentline(ci));
+    setobjs2s(L, L->top - 2, L->top - 1);  /* remove 'msg' from the stack */
+    L->top--;
+  }
   luaG_errormsg(L);
 }
 
diff --git a/lvm.c b/lvm.c
index e8c2e9627..cd992aada 100644
--- a/src/lvm.c
+++ b/src/lvm.c
@@ -656,8 +656,10 @@ void luaV_concat (lua_State *L, int total) {
       /* collect total length and number of strings */
       for (n = 1; n < total && tostring(L, s2v(top - n - 1)); n++) {
         size_t l = vslen(s2v(top - n - 1));
-        if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl))
+        if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl)) {
+          L->top = top - total;  /* pop strings to avoid wasting stack */
           luaG_runerror(L, "string length overflow");
+        }
         tl += l;
       }
       if (tl <= LUAI_MAXSHORTLEN) {  /* is result a short string? */
@@ -672,7 +674,7 @@ void luaV_concat (lua_State *L, int total) {
       setsvalue2s(L, top - n, ts);  /* create result */
     }
     total -= n-1;  /* got 'n' strings to create 1 new */
-    L->top -= n-1;  /* popped 'n' strings and pushed one */
+    L->top = top - (n - 1);  /* popped 'n' strings and pushed one */
   } while (total > 1);  /* repeat until only 1 result left */
 }

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File luabugs4.patch of Package lua54 (Revision b37e5a09a1c9394b62f6ba2577116767)

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