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Date: Wed, 29 Aug 2018 19:27:04 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, x86@...nel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com, daniel@...earbox.net,
jannh@...gle.com, keescook@...omium.org, kristen@...ux.intel.com,
dave.hansen@...el.com, arjan@...ux.intel.com,
netdev@...r.kernel.org
Subject: Re: [PATCH v4 0/3] KASLR feature to randomize each loadable module
On Wed, Aug 29, 2018 at 03:59:36PM -0700, Rick Edgecombe wrote:
> Hi,
>
> This is v4 of the "KASLR feature to randomize each loadable module" patchset.
> The purpose is to increase the randomization and also to make the modules
> randomized in relation to each other instead of just the base, so that if one
> module leaks the location of the others can't be inferred. It is enabled for
> x86_64 for now.
>
> V4 is a few small fixes. I humbly think this is in pretty good shape at this
> point, unless anyone has any comments. The only other big change I was
> considering was moving the new randomization algorithm into vmalloc so it could
> be re-used for other architectures or possibly other vmalloc usages.
>
> A few words on how this was tested - As previously mentioned, the entropy
> estimates were done using extracted module text sizes from the in-tree modules.
> These were also used to run 100,000's of simulated module allocations by calling
> module_alloc from a test module, including testing until allocation failure. The
> simulations kept track of every allocation address to make sure there were no
> collisions, and verified memory was actually mapped.
>
> In addition the __vmalloc_node_try_addr function has a suite of unit tests that
> verify for a bunch of edge cases that it:
> - Allows for allocations when it should
> - Reports the right error code if it collides with a lazy-free area or real
> allocation
> - Verifies it frees a lazy free area when it should
>
> These synthetic tests were also how the performance metrics were gathered.
>
> Changes for V4:
> - Fix issue caused by KASAN, kmemleak being provided different allocation
> lengths (padding).
> - Avoid kmalloc until sure its needed in __vmalloc_node_try_addr.
> - Fix for debug file hang when the last VA is a lazy purge area
> - Fixed issues reported by 0-day build system.
>
> Changes for V3:
> - Code cleanup based on internal feedback. (thanks to Dave Hansen and Andriy
> Shevchenko)
> - Slight refactor of existing algorithm to more cleanly live along side new
> one.
> - BPF synthetic benchmark
I don't see this benchmark in this patch set.
Could you prepare it as a test in tools/testing/selftests/bpf/ ?
so we can double check what is being tested and run it regularly
like we do for all other tests in there.
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