Messages in this thread | | | Date | Thu, 7 Feb 2008 16:01:22 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] Document randomize_va_space and CONFIG_COMPAT_BRK (was Re: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking) |
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* Jiri Kosina <jkosina@suse.cz> wrote:
> On Thu, 7 Feb 2008, Ingo Molnar wrote: > > > i'm wondering about the following detail: i guess on 64-bit x86 > > kernels we could default to !CONFIG_COMPAT_BRK? In 1997 there was no > > 64-bit x86. Maybe for compat 32-bit binaries we could keep it off, > > but always do it for 64-bit binaries. > > So what do you think is proper behavior in situation when > CONFIG_COMPAT_BRK=N on 64bit kernel, and 32bit-binary is loaded in > 32bit emulation? > > We can either leave the brk as-is, but that is in contradiction to > user explictly specifying CONFIG_COMPAT_BRK=N. Is this what you > propose? > > Or we can randomize brk start in such situation, but that is the > behavior we currently automatically have due to CONFIG_COMPAT_BRK=N, > so no change is needed.
thinking about it ... i think we should just keep this simple, and when COMPAT_BRK=y then we disable brk randomization globally. If !COMPAT_BRK then we do brk randomization globally as well. (and that is probably what users want the sysctl to do anyway - users wont necessarily know whether the app breakage they want to solve is due to 32-bit or 64-bit.)
Ingo
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