On Sun 2008-05-18 18:38:14, Avi Kivity wrote:
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.
"Security hole unless arch maintainer does _foo_" sounds
scary. Especially when i386 is hard to fix...