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Fix minilua undefined behavior in bit.tohex.

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Note: this is not a vulnerability! minilua is only used during the LuaJIT
build process. It only runs controlled and static Lua code (DynASM),
which is entirely contained within this repo and does not trigger the
undefined behavior.

This change is solely for the benefit of others, who might possibly use
minilua for purposes other than running DynASM.

Reported by quart27219. #1424
This commit is contained in:
Mike Pall
2026-01-09 17:34:15 +01:00
parent 282e1a969d
commit 221ea00775
2 changed files with 4 additions and 4 deletions
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4
src/host/genminilua.lua
View File

@@ -90,11 +90,11 @@ static int bswap(lua_State *L){
UB b=barg(L,1);b=(b>>24)|((b>>8)&0xff00)|((b&0xff00)<<8)|(b<<24);BRET(b)}
static int tohex(lua_State *L){
UB b=barg(L,1);
int n=lua_isnone(L,2)?8:(int)barg(L,2);
UB n=lua_isnone(L,2)?8:barg(L,2);
const char *hexdigits="0123456789abcdef";
char buf[8];
int i;
if(n<0){n=-n;hexdigits="0123456789ABCDEF";}
if((int)n<0){n=~n+1;hexdigits="0123456789ABCDEF";}
if(n>8)n=8;
for(i=(int)n;--i>=0;){buf[i]=hexdigits[b&15];b>>=4;}
lua_pushlstring(L,buf,(size_t)n);

4
src/host/minilua.c
View File

@@ -7722,11 +7722,11 @@ static int bswap(lua_State*L){
UB b=barg(L,1);b=(b>>24)|((b>>8)&0xff00)|((b&0xff00)<<8)|(b<<24);BRET(b)}
static int tohex(lua_State*L){
UB b=barg(L,1);
int n=lua_isnone(L,2)?8:(int)barg(L,2);
UB n=lua_isnone(L,2)?8:barg(L,2);
const char*hexdigits="0123456789abcdef";
char buf[8];
int i;
if(n<0){n=-n;hexdigits="0123456789ABCDEF";}
if((int)n<0){n=~n+1;hexdigits="0123456789ABCDEF";}
if(n>8)n=8;
for(i=(int)n;--i>=0;){buf[i]=hexdigits[b&15];b>>=4;}
lua_pushlstring(L,buf,(size_t)n);