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SubjectRe: [PATCH] x86/mm: Prevent bogus warnings with "noexec=off"
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On 4/15/19 10:46 AM, Thomas Gleixner wrote:

> Xose reported warnings when NX is disabled on the kernel command line.

Thank you for doing the dirty work.

>
> __early_set_fixmap() triggers:
>
> attempted to set unsupported pgprot: 8000000000000163
> bits: 8000000000000000
> supported: 7fffffffffffffff
>
> WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/pgtable.h:537
> __early_set_fixmap+0xa2/0xff
>
> because it uses __default_kernel_pte_mask to mask out unsupported bits.
>
> Use __supported_pte_mask instead.
>
> Disabling NX on the command line also triggers the NX warning in the page
> table mapping check:
>
> WARNING: CPU: 1 PID: 1 at arch/x86/mm/dump_pagetables.c:262 note_page+0x2ae/0x650
> ....
>
> Make the warning depend on NX set in __supported_pte_mask.
>
> Reported-by: Xose Vazquez Perez <xose.vazquez@gmail.com>

And
Tested-by: Xose Vazquez Perez <xose.vazquez@gmail.com>

> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/x86/mm/dump_pagetables.c | 3 ++-
> arch/x86/mm/ioremap.c | 2 +-
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -259,7 +259,8 @@ static void note_wx(struct pg_state *st)
> #endif
> /* Account the WX pages */
> st->wx_pages += npages;
> - WARN_ONCE(1, "x86/mm: Found insecure W+X mapping at address %pS\n",
> + WARN_ONCE(__supported_pte_mask & _PAGE_NX,
> + "x86/mm: Found insecure W+X mapping at address %pS\n",
> (void *)st->start_address);
> }
>
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -825,7 +825,7 @@ void __init __early_set_fixmap(enum fixe
> pte = early_ioremap_pte(addr);
>
> /* Sanitize 'prot' against any unsupported bits: */
> - pgprot_val(flags) &= __default_kernel_pte_mask;
> + pgprot_val(flags) &= __supported_pte_mask;
>
> if (pgprot_val(flags))
> set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
>

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