From: Miroslav Benes <mbenes@suse.cz>
To: Kristen Carlson Accardi <kristen@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Kees Cook <keescook@chromium.org>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
arjan@linux.intel.com, x86@kernel.org,
linux-kernel@vger.kernel.org,
kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com,
live-patching@vger.kernel.org, Hongjiu Lu <hongjiu.lu@intel.com>,
joe.lawrence@redhat.com
Subject: Re: [PATCH v4 00/10] Function Granular KASLR
Date: Fri, 28 Aug 2020 12:21:13 +0200 (CEST) [thread overview]
Message-ID: <alpine.LSU.2.21.2008281216031.29208@pobox.suse.cz> (raw)
In-Reply-To: <46c49dec078cb8625a9c3a3cd1310a4de7ec760b.camel@linux.intel.com>
Leaving Josh's proposals here for reference...
> > I'm not sure how LTO does it, but a few more (half-brained) ideas
> > that
> > could work:
> >
> > 1) Add a field in kallsyms to keep track of a symbol's original
> > offset
> > before randomization/re-sorting. Livepatch could use that field
> > to
> > determine the original sympos.
> >
> > 2) In fgkaslr code, go through all the sections and mark the ones
> > which
> > have duplicates (i.e. same name). Then when shuffling the
> > sections,
> > skip a shuffle if it involves a duplicate section. That way all
> > the
> > duplicates would retain their original sympos.
> >
> > 3) Livepatch could uniquely identify symbols by some feature other
> > than
> > sympos. For example:
> >
> > Symbol/function size - obviously this would only work if
> > duplicately
> > named symbols have different sizes.
> >
> > Checksum - as part of a separate feature we're also looking at
> > giving
> > each function its own checksum, calculated based on its
> > instruction
> > opcodes. Though calculating checksums at runtime could be
> > complicated by IP-relative addressing.
> >
> > I'm thinking #1 or #2 wouldn't be too bad. #3 might be harder.
> >
>
> Hi there! I was trying to find a super easy way to address this, so I
> thought the best thing would be if there were a compiler or linker
> switch to just eliminate any duplicate symbols at compile time for
> vmlinux. I filed this question on the binutils bugzilla looking to see
> if there were existing flags that might do this, but H.J. Lu went ahead
> and created a new one "-z unique", that seems to do what we would need
> it to do.
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=26391
>
> When I use this option, it renames any duplicate symbols with an
> extension - for example duplicatefunc.1 or duplicatefunc.2. You could
> either match on the full unique name of the specific binary you are
> trying to patch, or you match the base name and use the extension to
> determine original position. Do you think this solution would work?
Yes, I think so (thanks, Joe, for testing!).
It looks cleaner to me than the options above, but it may just be a matter
of taste. Anyway, I'd go with full name matching, because -z unique-symbol
would allow us to remove sympos altogether, which is appealing.
> If
> so, I can modify livepatch to refuse to patch on duplicated symbols if
> CONFIG_FG_KASLR and when this option is merged into the tool chain I
> can add it to KBUILD_LDFLAGS when CONFIG_FG_KASLR and livepatching
> should work in all cases.
Ok.
Josh, Petr, would this work for you too?
Thanks
Miroslav
next prev parent reply other threads:[~2020-08-28 10:21 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 16:59 [PATCH v4 00/10] Function Granular KASLR Kristen Carlson Accardi
2020-07-17 16:59 ` [PATCH v4 01/10] objtool: Do not assume order of parent/child functions Kristen Carlson Accardi
2020-07-17 16:59 ` [PATCH v4 02/10] x86: tools/relocs: Support >64K section headers Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 03/10] x86/boot: Allow a "silent" kaslr random byte fetch Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 04/10] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 05/10] x86: Make sure _etext includes function sections Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 06/10] x86/tools: Add relative relocs for randomized functions Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 07/10] x86/boot/compressed: Avoid duplicate malloc() implementations Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 08/10] x86: Add support for function granular KASLR Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 09/10] kallsyms: Hide layout Kristen Carlson Accardi
2020-07-20 1:25 ` Kees Cook
2020-07-20 16:59 ` Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 10/10] module: Reorder functions Kristen Carlson Accardi
2020-07-28 17:29 ` Jessica Yu
2020-07-22 9:27 ` [PATCH v4 00/10] Function Granular KASLR Miroslav Benes
2020-07-22 14:39 ` Kees Cook
2020-07-22 14:51 ` Joe Lawrence
2020-07-22 14:56 ` Joe Lawrence
2020-07-22 18:24 ` Kristen Carlson Accardi
2020-07-22 16:07 ` Josh Poimboeuf
2020-07-22 19:42 ` Kees Cook
2020-07-22 19:56 ` Kristen Carlson Accardi
2020-07-22 21:33 ` Josh Poimboeuf
2020-08-21 23:02 ` Kristen Carlson Accardi
2020-08-25 16:16 ` Joe Lawrence
2020-08-28 10:21 ` Miroslav Benes [this message]
2020-08-28 19:24 ` Josh Poimboeuf
2021-01-23 22:59 ` Fangrui Song
2021-01-25 17:21 ` Josh Poimboeuf
2020-08-03 11:39 ` Evgenii Shatokhin
2020-08-03 17:45 ` Kees Cook
2020-08-03 18:17 ` Joe Lawrence
2020-08-03 19:38 ` Frank Ch. Eigler
2020-08-03 20:11 ` Kees Cook
2020-08-03 21:12 ` Frank Ch. Eigler
2020-08-03 21:41 ` Kees Cook
2020-08-04 0:48 ` Frank Ch. Eigler
2020-08-04 17:04 ` Jessica Yu
2020-08-04 18:23 ` Joe Lawrence
2020-08-07 16:38 ` Kristen Carlson Accardi
2020-08-07 17:20 ` Kees Cook
2020-08-10 16:10 ` Kristen Carlson Accardi
2020-08-12 17:18 ` Kristen Carlson Accardi
2020-08-06 15:32 ` Ingo Molnar
2020-08-06 19:24 ` Kristen Carlson Accardi
2020-08-06 19:27 ` Kees Cook
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