From 6298903e35217ab69c279056f925fb72900ce0b7 Mon Sep 17 00:00:00 2001 From: Roberto Ierusalimschy Date: Mon, 6 Jul 2020 12:11:54 -0300 Subject: [PATCH] Keep minimum size when shrinking a stack When shrinking a stack (during GC), do not make it smaller than the initial stack size. --- ldo.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) ==== end of original header ==== CVE: CVE-2020-15888 Upstream-Status: backport [https://github.com/lua/lua.git] Signed-off-by: Joe Slater ==== diff --git a/ldo.c b/ldo.c index c563b1d9..a89ac010 100644 --- a/src/ldo.c +++ b/src/ldo.c @@ -220,7 +220,7 @@ static int stackinuse (lua_State *L) { void luaD_shrinkstack (lua_State *L) { int inuse = stackinuse(L); - int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK; + int goodsize = inuse + BASIC_STACK_SIZE; if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK; /* respect stack limit */ if (L->stacksize > LUAI_MAXSTACK) /* had been handling stack overflow? */ @@ -229,8 +229,7 @@ void luaD_shrinkstack (lua_State *L) { luaE_shrinkCI(L); /* shrink list */ /* if thread is currently not handling a stack overflow and its good size is smaller than current size, shrink its stack */ - if (inuse <= (LUAI_MAXSTACK - EXTRA_STACK) && - goodsize < L->stacksize) + if (inuse <= (LUAI_MAXSTACK - EXTRA_STACK) && goodsize < L->stacksize) luaD_reallocstack(L, goodsize); else /* don't change stack */ condmovestack(L,{},{}); /* (change only for debugging) */ -- 2.17.1