Re: [RFC][PATCH] linux-2.6.2_vsyscall-gtod_B2.patch

[Ulrich Drepper]

Andrea Arcangeli wrote:

> with regards to Ulrich's security related comments, this won't make any
> difference compared to the fixed address version either, since the
> vsyscall page is still at a fixed address in the fixmap area,

Gee, you don't want to understand it.

Even if the official kernel's handling of the vdso puts it at the same
address all the time this does not mean this can be engraved in stone.
It must be possible to move the page.  And I expect this will be the
case in our kernels.

It is completely unacceptable to use fixed addresses or require the libc
to be recompiled for a new address.  At the highest security level the
vdso address should vary from program run to program run which means
there is no way to change the libc.

-- 
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â
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