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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".
CVE: CVE-2022-33099
Upstream-Status: Backport [https://github.com/lua/lua/commit/42d40581dd919fb134c07027ca1ce0844c670daf]
Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
ldebug.c | 5 ++++-
lvm.c | 6 ++++--
2 files changed, 8 insertions(+), 3 deletions(-)
--- a/src/ldebug.c
+++ b/src/ldebug.c
@@ -824,8 +824,11 @@ l_noret luaG_runerror (lua_State *L, con
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);
}
--- a/src/lvm.c
+++ b/src/lvm.c
@@ -656,8 +656,10 @@ void luaV_concat (lua_State *L, int tota
/* 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 tota
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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