linux-kernel - Re: [PATCH v2 1/1] x86/mm/KASLR: Store pud_page

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Message-ID: <20230619104308.GC1472962@google.com>
Date:   Mon, 19 Jun 2023 11:43:08 +0100
From:   Lee Jones <lee@...nel.org>
To:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] x86/mm/KASLR: Store pud_page_tramp into entry
 rather than page

On Fri, 16 Jun 2023, Lee Jones wrote:

> On Wed, 14 Jun 2023, Lee Jones wrote:
> 
> > set_pgd() expects to be passed whole pages to operate on, whereas
> > trampoline_pgd_entry is, as the name suggests, an entry.  The
> > ramifications for using set_pgd() here are that the following thread of
> > execution will not only place the suggested value into the
> > trampoline_pgd_entry (8-Byte globally stored [.bss]) variable, PTI will
> > also attempt to replicate that value into the non-existent neighboring
> > user page (located +4k away), leading to the corruption of other global
> > [.bss] stored variables.
> > 
> > Suggested-by: Dave Hansen <dave.hansen@...ux.intel.com>
> > Signed-off-by: Lee Jones <lee@...nel.org>
> > ---
> >  arch/x86/mm/kaslr.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> Is there any more you need from me at this point?
> 
> Would you like me to resubmit with the Fixes: tag applied, or is
> someone happy to apply it on merge?

Superstar, thanks Dave.

-- 
Lee Jones [李琼斯]