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