Re: [PATCH] Make LIST_POISON less deadly

From: Avi Kivity
Date: Tue May 20 2008 - 12:50:26 EST

Pavel Machek wrote:
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...

It's a potential security hole. You need to find a list corruption first. The patch prevents escalation of the oops into a code injection.

i386 is fixable, though it will take more work than x86_64.

error compiling committee.c: too many arguments to function

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