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    Subject[PATCH AUTOSEL 5.6 150/606] powerpc/64s: Disable STRICT_KERNEL_RWX
    Date
    From: Michael Ellerman <mpe@ellerman.id.au>

    commit 8659a0e0efdd975c73355dbc033f79ba3b31e82c upstream.

    Several strange crashes have been eventually traced back to
    STRICT_KERNEL_RWX and its interaction with code patching.

    Various paths in our ftrace, kprobes and other patching code need to
    be hardened against patching failures, otherwise we can end up running
    with partially/incorrectly patched ftrace paths, kprobes or jump
    labels, which can then cause strange crashes.

    Although fixes for those are in development, they're not -rc material.

    There also seem to be problems with the underlying strict RWX logic,
    which needs further debugging.

    So for now disable STRICT_KERNEL_RWX on 64-bit to prevent people from
    enabling the option and tripping over the bugs.

    Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs")
    Cc: stable@vger.kernel.org # v4.13+
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20200520133605.972649-1-mpe@ellerman.id.au
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/powerpc/Kconfig | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
    index 497b7d0b2d7e..b0fb42b0bf4b 100644
    --- a/arch/powerpc/Kconfig
    +++ b/arch/powerpc/Kconfig
    @@ -129,7 +129,7 @@ config PPC
    select ARCH_HAS_PTE_SPECIAL
    select ARCH_HAS_MEMBARRIER_CALLBACKS
    select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
    - select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
    + select ARCH_HAS_STRICT_KERNEL_RWX if (PPC32 && !HIBERNATION)
    select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
    select ARCH_HAS_UACCESS_FLUSHCACHE
    select ARCH_HAS_UACCESS_MCSAFE if PPC64
    --
    2.25.1
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