From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Song Liu <songliubraving@fb.com>,
Joerg Roedel <jroedel@suse.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Rik van Riel <riel@surriel.com>
Subject: Re: [patch 2/2] x86/mm/pti: Do not invoke PTI functions when PTI is disabled
Date: Wed, 28 Aug 2019 21:00:06 +0200 [thread overview]
Message-ID: <20190828190006.GB77809@gmail.com> (raw)
In-Reply-To: <20190828143124.063353972@linutronix.de>
* Thomas Gleixner <tglx@linutronix.de> wrote:
> When PTI is disabled at boot time either because the CPU is not affected or
> PTI has been disabled on the command line, the boot code still calls into
> pti_finalize() which then unconditionally invokes:
>
> pti_clone_entry_text()
> pti_clone_kernel_text()
>
> pti_clone_kernel_text() was called unconditionally before the 32bit support
> was added and 32bit added the call to pti_clone_entry_text().
>
> The call has no side effects as cloning the page tables into the available
> second one, which was allocated for PTI does not create damage. But it does
> not make sense either and in case that this functionality would be extended
> later this might actually lead to hard to diagnose issue.
s/issue/issues
> Neither function should be called when PTI is runtime disabled. Make the
> invocation conditional.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/x86/mm/pti.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> --- a/arch/x86/mm/pti.c
> +++ b/arch/x86/mm/pti.c
> @@ -668,6 +668,8 @@ void __init pti_init(void)
> */
> void pti_finalize(void)
> {
> + if (!boot_cpu_has(X86_FEATURE_PTI))
> + return;
> /*
> * We need to clone everything (again) that maps parts of the
> * kernel image.
Acked-by: Ingo Molnar <mingo@kernel.org>
Thanks,
Ingo
next prev parent reply other threads:[~2019-08-28 19:00 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-28 14:24 [patch 0/2] x86/mm/pti: Robustness updates Thomas Gleixner
2019-08-28 14:24 ` [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable() Thomas Gleixner
2019-08-28 15:46 ` Dave Hansen
2019-08-28 15:51 ` Thomas Gleixner
2019-08-28 17:58 ` Song Liu
2019-08-28 20:05 ` Thomas Gleixner
2019-08-28 20:32 ` Song Liu
2019-08-28 22:31 ` [PATCH] x86/mm/cpa: Prevent large page split when ftrace flips RW on kernel text Thomas Gleixner
2019-08-28 23:03 ` Song Liu
2019-08-29 13:01 ` Peter Zijlstra
2019-08-29 18:55 ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
2019-08-28 18:58 ` [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable() Ingo Molnar
2019-08-28 19:45 ` Thomas Gleixner
2019-08-28 20:54 ` [patch V2 " Thomas Gleixner
2019-08-28 21:52 ` Thomas Gleixner
2019-08-28 21:54 ` [patch V3 " Thomas Gleixner
2019-08-28 23:22 ` Ingo Molnar
2019-08-29 19:02 ` [tip: x86/pti] " tip-bot2 for Song Liu
2019-08-30 10:24 ` [patch V3 1/2] " Joerg Roedel
2019-08-28 14:24 ` [patch 2/2] x86/mm/pti: Do not invoke PTI functions when PTI is disabled Thomas Gleixner
2019-08-28 15:47 ` Dave Hansen
2019-08-28 17:49 ` Song Liu
2019-08-28 19:00 ` Ingo Molnar [this message]
2019-08-29 19:02 ` [tip: x86/pti] " tip-bot2 for Thomas Gleixner
2019-08-30 10:25 ` [patch 2/2] " Joerg Roedel
2019-08-28 16:03 ` [patch 0/2] x86/mm/pti: Robustness updates Peter Zijlstra
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