Avi Kivity <avi@xxxxxxxxxxxx> writes:
The list macros use LIST_POISON1 and LIST_POISON2 as undereferencable
pointers in order to trap erronous use of freed list_heads. Unfortunately
userspace can arrange for those pointers to actually be dereferencable,
potentially turning an oops to an expolit.
To avoid this allow architectures (currently x86_64 only) to override
the default values for these pointers with truly-undereferncable values.
This is easy on x86_64 as the virtual address space is smaller than
the range spanned by pointer values.
Hmm, thought I had sent a reply earlier, but don't see it so again.
My apologies if you see it twice.
The problem with your address values is that they're non canonical
and will result in a #GP, not #PF and oops handler cannot display
the address which will make them much less obvious.
I would rather use a guaranteed to be unmapped but canonical
address like in the ffffc10000000000 - ffffc1ffffffffff range
so that you still get page faults.