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From 0718b375425aad8e54e1150313b862e4c6fd324a Mon Sep 17 00:00:00 2001
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From: Kevin Atkinson <kevina@gnu.org>
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Date: Sat, 21 Dec 2019 20:32:47 +0000
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Subject: [PATCH] objstack: assert that the alloc size will fit within a chunk
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to prevent a buffer overflow
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Bug found using OSS-Fuze.
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---
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common/objstack.hpp | 18 ++++++++++++++----
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1 file changed, 14 insertions(+), 4 deletions(-)
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diff --git a/common/objstack.hpp b/common/objstack.hpp
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index 3997bf7..bd97ccd 100644
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--- a/common/objstack.hpp
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+++ b/common/objstack.hpp
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@@ -5,6 +5,7 @@
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#include "parm_string.hpp"
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#include <stdlib.h>
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#include <assert.h>
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+#include <stddef.h>
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namespace acommon {
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@@ -26,6 +27,12 @@ class ObjStack
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byte * temp_end;
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void setup_chunk();
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void new_chunk();
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+ bool will_overflow(size_t sz) const {
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+ return offsetof(Node,data) + sz > chunk_size;
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+ }
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+ void check_size(size_t sz) {
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+ assert(!will_overflow(sz));
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+ }
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ObjStack(const ObjStack &);
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void operator=(const ObjStack &);
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@@ -56,7 +63,7 @@ class ObjStack
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void * alloc_bottom(size_t size) {
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byte * tmp = bottom;
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bottom += size;
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- if (bottom > top) {new_chunk(); tmp = bottom; bottom += size;}
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+ if (bottom > top) {check_size(size); new_chunk(); tmp = bottom; bottom += size;}
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return tmp;
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}
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// This alloc_bottom will insure that the object is aligned based on the
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@@ -66,7 +73,7 @@ class ObjStack
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align_bottom(align);
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byte * tmp = bottom;
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bottom += size;
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- if (bottom > top) {new_chunk(); goto loop;}
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+ if (bottom > top) {check_size(size); new_chunk(); goto loop;}
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return tmp;
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}
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char * dup_bottom(ParmString str) {
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@@ -79,7 +86,7 @@ class ObjStack
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// always be aligned as such.
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void * alloc_top(size_t size) {
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top -= size;
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- if (top < bottom) {new_chunk(); top -= size;}
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+ if (top < bottom) {check_size(size); new_chunk(); top -= size;}
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return top;
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}
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// This alloc_top will insure that the object is aligned based on
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@@ -88,7 +95,7 @@ class ObjStack
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{loop:
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top -= size;
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align_top(align);
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- if (top < bottom) {new_chunk(); goto loop;}
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+ if (top < bottom) {check_size(size); new_chunk(); goto loop;}
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return top;
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}
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char * dup_top(ParmString str) {
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@@ -117,6 +124,7 @@ class ObjStack
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void * alloc_temp(size_t size) {
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temp_end = bottom + size;
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if (temp_end > top) {
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+ check_size(size);
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new_chunk();
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temp_end = bottom + size;
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}
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@@ -131,6 +139,7 @@ class ObjStack
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} else {
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size_t s = temp_end - bottom;
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byte * p = bottom;
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+ check_size(size);
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new_chunk();
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memcpy(bottom, p, s);
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temp_end = bottom + size;
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@@ -150,6 +159,7 @@ class ObjStack
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} else {
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size_t s = temp_end - bottom;
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byte * p = bottom;
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+ check_size(size);
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new_chunk();
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memcpy(bottom, p, s);
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temp_end = bottom + size;
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