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SubjectRe: [PATCH] lkdtm: Keep the rodata test from causing retbleed WARNINGS
On Wed, Jul 20, 2022 at 01:13:05PM -0700, Kees Cook wrote:
> On Wed, Jul 20, 2022 at 03:55:07PM -0400, Steven Rostedt wrote:
> > From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> >
> > The rodata test checks if executable code in the .rodata section will not
> > execute. But this also means that fix ups that the return hook code does
> > will not be able to change this code at boot up, and this causes a
> > warning.
> >
> > By removing the RETHOOK_CFLAGS from the compilation of the rodata function
> > makes it hidden from objtool and it will not add its return hook into the
> > .returns section. This keeps the fix up code from trying and failing on
> > modifying the rodata return call.
> >
> > Link: https://lore.kernel.org/all/20220720125736.48164a14@gandalf.local.home/
> >
> > Fixes: ee88d363d1561 ("x86,static_call: Use alternative RET encoding")
> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
>
> Yeah, this matches a portion of what was suggested:
> https://lore.kernel.org/lkml/20220713213133.455599-1-keescook@chromium.org/
>
> But it still needed objtool fixes:
> https://lore.kernel.org/lkml/20220715032333.neywlazczbb35w3b@treble/
>
> Perhaps objtool has already had patches landed for this? (Otherwise the
> patch you suggested would fail to build on x86 with rethunk support.)

I send this patch out a few days ago, nobody picked it up yet:

https://lkml.kernel.org/lkml/8ec0039712f252693049c70ed3891d39a2357112.1658155446.git.jpoimboe@kernel.org

--
Josh

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