Re: Patch 4/6 randomize the stack pointer

[John Richard Moser]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1



Linus Torvalds wrote:
> 

[...]

> 
> Your suggestion of 256MB of randomization for the stack SIMPLY IS NOT 
> ACCEPTABLE for a lot of uses. People on 32-bit archtiectures have issues 
> with usable virtual memory areas etc.
> 

I feel the need to point something out here.

[TEXT][BRK][MMAP---------------][STACK]

Here's a normal layout.

[TEXT][BRK][MMAP-------][STACK][MMAP--]

Is this one any worse?  Just bias non-executable mappings above the
stack when, say, half of VMA is used up.  Prevent executable mappings
from being created up there because PaX' PAGEEXEC and Exec Shield's
emulation will be affected by a high-mapping (PaX falls back to
kernel-assisted MMU walking, which can be very high overhead; ES just
makes everything below the area executable).

So, you can do it without losing VMA, in theory.


[...]

> 

- --
All content of all messages exchanged herein are left in the
Public Domain, unless otherwise explicitly stated.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.0 (GNU/Linux)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

iD8DBQFB+V94hDd4aOud5P8RAqv1AJ9iazEKh//yeaTdraUou9KLQCUG0wCfVbo2
kXYvkauZ8+wC7J3nN5IzoTY=
=tvyp
-----END PGP SIGNATURE-----
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/