[scudo] GWP_ASAN runs on untagged pointers

[vitalybuka]

Summary

It's already covered by multiple tests, but to trigger
this path we need MTE+GWP which disabled.

[hctim]

Nice find! Thanks!

[pcc]

LGTM

compiler-rt/lib/scudo/standalone/combined.h

void *reallocate(void *OldPtr, uptr NewSize, uptr Alignment = MinAlignment) {
 
     const Options Options = Primary.Options.load();
     if (UNLIKELY(NewSize >= MaxAllowedMallocSize)) {
       if (Options.get(OptionBit::MayReturnNull))
         return nullptr;
       reportAllocationSizeTooBig(NewSize, 0, MaxAllowedMallocSize);
     }
 
-    void *OldTaggedPtr = OldPtr;
-    OldPtr = getHeaderTaggedPointer(OldPtr);
-
     // The following cases are handled by the C wrappers.
     DCHECK_NE(OldPtr, nullptr);
     DCHECK_NE(NewSize, 0);
 
 #ifdef GWP_ASAN_HOOKS
     if (UNLIKELY(GuardedAlloc.pointerIsMine(OldPtr))) {
       uptr OldSize = GuardedAlloc.getSize(OldPtr);
       void *NewPtr = allocate(NewSize, Chunk::Origin::Malloc, Alignment);
       if (NewPtr)
         memcpy(NewPtr, OldPtr, (NewSize < OldSize) ? NewSize : OldSize);
       GuardedAlloc.deallocate(OldPtr);
       Stats.lock();
       Stats.add(StatFree, GuardedAllocSlotSize);
       Stats.sub(StatAllocated, GuardedAllocSlotSize);
       Stats.unlock();
       return NewPtr;
     }
 #endif // GWP_ASAN_HOOKS
 
+    void *OldTaggedPtr = OldPtr;
+    OldPtr = getHeaderTaggedPointer(OldPtr);
+
     if (UNLIKELY(!isAligned(reinterpret_cast<uptr>(OldPtr), MinAlignment)))
       reportMisalignedPointer(AllocatorAction::Reallocating, OldPtr);
 
     Chunk::UnpackedHeader OldHeader;
     Chunk::loadHeader(Cookie, OldPtr, &OldHeader);
 
     if (UNLIKELY(OldHeader.State != Chunk::State::Allocated))
       reportInvalidChunkState(AllocatorAction::Reallocating, OldPtr);