llvm dev - Sep 2018 - suggested bug fix in RTDyldObjectLinkingLayer

In certain circumstances, RTDyldObjectLinkingLayer dereferences a null
pointer. Specifically, that happens if you add a linking object which,
for some reason, is never finalized, and you specify a function to be
called when objects are freed. Admittedly, that must not happen very
often, but it can happen in our application, causing it to crash.

Might I suggest the following patch?

Geoff

--- RTDyldObjectLinkingLayer.h  (revision 342448)
+++ RTDyldObjectLinkingLayer.h  (working copy)
@@ -175,7 +175,7 @@
     }

     ~ConcreteLinkedObject() override {
-      if (this->Parent.NotifyFreed)
+      if (this->Parent.NotifyFreed && ObjForNotify.getBinary())
         this->Parent.NotifyFreed(K, *ObjForNotify.getBinary());

       MemMgr->deregisterEHFrames();

/cc Lang
> On 18. Sep 2018, at 10:36, Geoff Levner via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> In certain circumstances, RTDyldObjectLinkingLayer dereferences a null
> pointer. Specifically, that happens if you add a linking object which,
> for some reason, is never finalized, and you specify a function to be
> called when objects are freed. Admittedly, that must not happen very
> often, but it can happen in our application, causing it to crash.
> 
> Might I suggest the following patch?
> 
> Geoff
> 
> --- RTDyldObjectLinkingLayer.h  (revision 342448)
> +++ RTDyldObjectLinkingLayer.h  (working copy)
> @@ -175,7 +175,7 @@
>     }
> 
>     ~ConcreteLinkedObject() override {
> -      if (this->Parent.NotifyFreed)
> +      if (this->Parent.NotifyFreed && ObjForNotify.getBinary())
>         this->Parent.NotifyFreed(K, *ObjForNotify.getBinary());
> 
>       MemMgr->deregisterEHFrames();
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Hi Geoff,

Thanks for catching that. I think your fix is the right one. I have
committed it in r342783.

Cheers,
Lang.

On Thu, Sep 20, 2018 at 12:29 PM Alex Denisov <1101.debian at gmail.com>
wrote:
> /cc Lang
>
> > On 18. Sep 2018, at 10:36, Geoff Levner via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > In certain circumstances, RTDyldObjectLinkingLayer dereferences a null
> > pointer. Specifically, that happens if you add a linking object which,
> > for some reason, is never finalized, and you specify a function to be
> > called when objects are freed. Admittedly, that must not happen very
> > often, but it can happen in our application, causing it to crash.
> >
> > Might I suggest the following patch?
> >
> > Geoff
> >
> > --- RTDyldObjectLinkingLayer.h  (revision 342448)
> > +++ RTDyldObjectLinkingLayer.h  (working copy)
> > @@ -175,7 +175,7 @@
> >     }
> >
> >     ~ConcreteLinkedObject() override {
> > -      if (this->Parent.NotifyFreed)
> > +      if (this->Parent.NotifyFreed &&
ObjForNotify.getBinary())
> >         this->Parent.NotifyFreed(K, *ObjForNotify.getBinary());
> >
> >       MemMgr->deregisterEHFrames();
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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