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Fix sanitizer/67258 by cherry picking upstream patch 

PR sanitizer/67258
	* ubsan/ubsan_type_hash.cc: Cherry pick upstream r244101.

Upstraem patch:
commit 1d2477faafda9ad2cc19927b3c31efd22747f013
Author: Alexey Samsonov <vonosmas@gmail.com>
Date:   Wed Aug 5 19:35:46 2015 +0000

    [UBSan] Fix UBSan-vptr false positive.

    Offset from vptr to the start of most-derived object can actually
    be positive in some virtual base class vtables.

    Patch by Stephan Bergmann!

    git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@244101 91177308-0d34-0410-b5e6-96231b3b80d8

From-SVN: r227591
This commit is contained in:
Markus Trippelsdorf 2015-09-09 16:34:59 +00:00 committed by Markus Trippelsdorf
parent 34bc1d225c
commit 1842a04ce0
3 changed files with 23 additions and 3 deletions
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15
gcc/testsuite/g++.dg/ubsan/vptr-10.C Normal file
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@ -0,0 +1,15 @@
// { dg-do run }
// { dg-options "-fsanitize=vptr -fno-sanitize-recover=vptr" }
struct A
{
virtual ~A() {}
};
struct B : virtual A {};
struct C : virtual A {};
struct D : B, virtual C {};
int main()
{
D d;
}

5
libsanitizer/ChangeLog
View File

@ -1,3 +1,8 @@
2015-09-09 Markus Trippelsdorf <markus@trippelsdorf.de>
PR sanitizer/67258
* ubsan/ubsan_type_hash.cc: Cherry pick upstream r244101.
2015-07-29 Markus Trippelsdorf <markus@trippelsdorf.de>
PR sanitizer/63927

6
libsanitizer/ubsan/ubsan_type_hash.cc
View File

@ -186,8 +186,8 @@ namespace {
struct VtablePrefix {
/// The offset from the vptr to the start of the most-derived object.
/// This should never be greater than zero, and will usually be exactly
/// zero.
/// This will only be greater than zero in some virtual base class vtables
/// used during object con-/destruction, and will usually be exactly zero.
sptr Offset;
/// The type_info object describing the most-derived class type.
std::type_info *TypeInfo;
@ -197,7 +197,7 @@ VtablePrefix *getVtablePrefix(void *Object) {
if (!*VptrPtr)
return 0;
VtablePrefix *Prefix = *VptrPtr - 1;
if (Prefix->Offset > 0 || !Prefix->TypeInfo)
if (!Prefix->TypeInfo)
// This can't possibly be a valid vtable.
return 0;
return Prefix;