Theo de Raadt wrote:
> > Mark Kettenis wrote:
> > > CVSROOT: /cvs
> > > Module name: src
> > > Changes by: kette...@cvs.openbsd.org 2016/05/14 08:24:54
> > >
> > > Modified files:
> > > lib/libkvm : kvm.c
> > >
> > > Log message:
> > > Revert previous commit. Converting bcopy into memcpy is never safe when
> > > there is a big fat comment saying "Avoid alignment issues" immediately
> > > above them.
> >
> > what? memcpy works on unaligned memory just fine.
> >
>
> not when the compiler thinks "hey i can do this myself, and i am damn
> sure it is aligned".
>
> then memcpy/memmove fail, whereas bcopy works.
ok, so the real problem here is that we're creating unaligned pointers. this
is illegal C even when calling bcopy, we just get away with it. *for now.*
fix that first by avoiding unsafe casts.
Index: kvm.c
===================================================================
RCS file: /cvs/src/lib/libkvm/kvm.c,v
retrieving revision 1.61
diff -u -p -r1.61 kvm.c
--- kvm.c 14 May 2016 14:24:54 -0000 1.61
+++ kvm.c 14 May 2016 16:57:07 -0000
@@ -44,6 +44,7 @@
#include <sys/exec.h>
#include <sys/kcore.h>
+#include <stddef.h>
#include <errno.h>
#include <ctype.h>
#include <db.h>
@@ -791,9 +792,9 @@ kvm_nlist(kvm_t *kd, struct nlist *nl)
/*
* Avoid alignment issues.
*/
- bcopy(&((struct nlist *)rec.data)->n_type,
+ bcopy((char *)rec.data + offsetof(struct nlist, n_type),
&p->n_type, sizeof(p->n_type));
- bcopy(&((struct nlist *)rec.data)->n_value,
+ bcopy((char *)rec.data + offsetof(struct nlist, n_value),
&p->n_value, sizeof(p->n_value));
}
/*
