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    Subject[PATCH 5.0 048/137] x86/mm: Prevent bogus warnings with "noexec=off"
    Date
    [ Upstream commit 510bb96fe5b3480b4b22d815786377e54cb701e7 ]

    Xose Vazquez Perez reported boot warnings when NX is disabled on the kernel command line.

    __early_set_fixmap() triggers this warning:

    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>
    Tested-by: Xose Vazquez Perez <xose.vazquez@gmail.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rik van Riel <riel@surriel.com>
    Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1904151037530.1729@nanos.tec.linutronix.de
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/mm/dump_pagetables.c | 3 ++-
    arch/x86/mm/ioremap.c | 2 +-
    2 files changed, 3 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
    index e3cdc85ce5b6e..84304626b1cb8 100644
    --- 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);
    }

    diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
    index 5378d10f1d31d..3b76fe954978c 100644
    --- a/arch/x86/mm/ioremap.c
    +++ b/arch/x86/mm/ioremap.c
    @@ -825,7 +825,7 @@ void __init __early_set_fixmap(enum fixed_addresses idx,
    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));
    --
    2.20.1


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