From f7e6eaf84bebac565f462e2ce48f30808cc771eb Mon Sep 17 00:00:00 2001
From: David Kalnischkies <david@kalnischkies.de>
Date: Mon, 8 Jun 2020 17:07:43 +0200
Subject: Avoid undefined pointer arithmetic while growing mmap
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The undefined behaviour sanitizer complains with:
runtime error: addition of unsigned offset to 0x… overflowed to 0x…

Compilers and runtime do the right thing in any case and it is a
codepath that can (and ideally should) be avoided for speed reasons
alone, but fixing it can't hurt (too much).
---
 apt-pkg/cacheiterators.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'apt-pkg/cacheiterators.h')

diff --git a/apt-pkg/cacheiterators.h b/apt-pkg/cacheiterators.h
index 6261b5089..466492442 100644
--- a/apt-pkg/cacheiterators.h
+++ b/apt-pkg/cacheiterators.h
@@ -82,10 +82,10 @@ template<typename Str, typename Itr> class APT_PUBLIC pkgCache::Iterator :
 	inline unsigned long Index() const {return S - OwnerPointer();}
 	inline map_pointer<Str> MapPointer() const {return map_pointer<Str>(Index()) ;}
 
-	void ReMap(void const * const oldMap, void const * const newMap) {
+	void ReMap(void const * const oldMap, void * const newMap) {
 		if (Owner == 0 || S == 0)
 			return;
-		S += static_cast<Str const *>(newMap) - static_cast<Str const *>(oldMap);
+		S = static_cast<Str *>(newMap) + (S - static_cast<Str const *>(oldMap));
 	}
 
 	// Constructors - look out for the variable assigning
@@ -350,12 +350,12 @@ class APT_PUBLIC pkgCache::DepIterator : public Iterator<Dependency, DepIterator
 	};
 	inline DependencyProxy operator->() const {return (DependencyProxy) { S2->Version, S2->Package, S->ID, S2->Type, S2->CompareOp, S->ParentVer, S->DependencyData, S->NextRevDepends, S->NextDepends, S2->NextData };}
 	inline DependencyProxy operator->() {return (DependencyProxy) { S2->Version, S2->Package, S->ID, S2->Type, S2->CompareOp, S->ParentVer, S->DependencyData, S->NextRevDepends, S->NextDepends, S2->NextData };}
-	void ReMap(void const * const oldMap, void const * const newMap)
+	void ReMap(void const * const oldMap, void * const newMap)
 	{
 		Iterator<Dependency, DepIterator>::ReMap(oldMap, newMap);
 		if (Owner == 0 || S == 0 || S2 == 0)
 			return;
-		S2 += static_cast<DependencyData const *>(newMap) - static_cast<DependencyData const *>(oldMap);
+		S2 = static_cast<DependencyData *>(newMap) + (S2 - static_cast<DependencyData const *>(oldMap));
 	}
 
 	//Nice printable representation
-- 
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