Re: [PATCH 1/5] x86, pti: fix boot problems from Global-bit setting

Aaro Koskinen
2018-04-23T10:50:50Z

Hi,

On Fri, Apr 20, 2018 at 03:20:19PM -0700, Dave Hansen wrote:
> Part of the global bit _setting_ patches also includes clearing the
> Global bit when we do not want it. That is done with
> set_memory_nonglobal(), which uses change_page_attr_clear() in
> pageattr.c under the covers.
>
> The TLB flushing code inside pageattr.c has has checks like
> BUG_ON(irqs_disabled()), looking for interrupt disabling that might
> cause deadlocks. But, these also trip in early boot on certain
> preempt configurations. Just copy the existing BUG_ON() sequence from
> cpa_flush_range() to the other two sites and check for early boot.
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Fixes: 39114b7a7 (x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image)
> Reported-by: Mariusz Ceier <mceier@gmail.com>
> Reported-by: Aaro Koskinen <aaro.koskinen@nokia.com>

Tested-by: Aaro Koskinen <aaro.koskinen@nokia.com>

A.

> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Arjan van de Ven <arjan@linux.intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Juergen Gross <jgross@suse.com>
> Cc: Kees Cook <keescook@google.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Nadav Amit <namit@vmware.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-mm@kvack.org
> ---
>
> b/arch/x86/mm/pageattr.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff -puN arch/x86/mm/pageattr.c~pti-glb-boot-problem-fix arch/x86/mm/pageattr.c
> --- a/arch/x86/mm/pageattr.c~pti-glb-boot-problem-fix 2018-04-20 14:10:01.086749169 -0700
> +++ b/arch/x86/mm/pageattr.c 2018-04-20 14:10:01.090749169 -0700
> @@ -172,7 +172,7 @@ static void __cpa_flush_all(void *arg)
>
> static void cpa_flush_all(unsigned long cache)
> {
> - BUG_ON(irqs_disabled());
> + BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
>
> on_each_cpu(__cpa_flush_all, (void *) cache, 1);
> }
> @@ -236,7 +236,7 @@ static void cpa_flush_array(unsigned lon
> unsigned long do_wbinvd = cache && numpages >= 1024; /* 4M threshold */
> #endif
>
> - BUG_ON(irqs_disabled());
> + BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
>
> on_each_cpu(__cpa_flush_all, (void *) do_wbinvd, 1);
>
> _