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Message-ID: <20200828192413.p6rctr42xtuh2c2e@treble>
Date: Fri, 28 Aug 2020 14:24:13 -0500
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Miroslav Benes <mbenes@...e.cz>
Cc: Kristen Carlson Accardi <kristen@...ux.intel.com>,
Kees Cook <keescook@...omium.org>, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, arjan@...ux.intel.com,
x86@...nel.org, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com, rick.p.edgecombe@...el.com,
live-patching@...r.kernel.org, Hongjiu Lu <hongjiu.lu@...el.com>,
joe.lawrence@...hat.com
Subject: Re: [PATCH v4 00/10] Function Granular KASLR
On Fri, Aug 28, 2020 at 12:21:13PM +0200, Miroslav Benes wrote:
> > 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?
Sounds good to me. Kristen, thanks for finding a solution!
--
Josh
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