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    Subject[PATCH 5.15 019/171] efi: runtime: avoid EFIv2 runtime services on Apple x86 machines
    Date
    From: Ard Biesheuvel <ardb@kernel.org>

    commit f5390cd0b43c2e54c7cf5506c7da4a37c5cef746 upstream.

    Aditya reports [0] that his recent MacbookPro crashes in the firmware
    when using the variable services at runtime. The culprit appears to be a
    call to QueryVariableInfo(), which we did not use to call on Apple x86
    machines in the past as they only upgraded from EFI v1.10 to EFI v2.40
    firmware fairly recently, and QueryVariableInfo() (along with
    UpdateCapsule() et al) was added in EFI v2.00.

    The only runtime service introduced in EFI v2.00 that we actually use in
    Linux is QueryVariableInfo(), as the capsule based ones are optional,
    generally not used at runtime (all the LVFS/fwupd firmware update
    infrastructure uses helper EFI programs that invoke capsule update at
    boot time, not runtime), and not implemented by Apple machines in the
    first place. QueryVariableInfo() is used to 'safely' set variables,
    i.e., only when there is enough space. This prevents machines with buggy
    firmwares from corrupting their NVRAMs when they run out of space.

    Given that Apple machines have been using EFI v1.10 services only for
    the longest time (the EFI v2.0 spec was released in 2006, and Linux
    support for the newly introduced runtime services was added in 2011, but
    the MacbookPro12,1 released in 2015 still claims to be EFI v1.10 only),
    let's avoid the EFI v2.0 ones on all Apple x86 machines.

    [0] https://lore.kernel.org/all/6D757C75-65B1-468B-842D-10410081A8E4@live.com/

    Cc: <stable@vger.kernel.org>
    Cc: Jeremy Kerr <jk@ozlabs.org>
    Cc: Matthew Garrett <mjg59@srcf.ucam.org>
    Reported-by: Aditya Garg <gargaditya08@live.com>
    Tested-by: Orlando Chamberlain <redecorating@protonmail.com>
    Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
    Tested-by: Aditya Garg <gargaditya08@live.com>
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=215277
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/firmware/efi/efi.c | 7 +++++++
    1 file changed, 7 insertions(+)

    --- a/drivers/firmware/efi/efi.c
    +++ b/drivers/firmware/efi/efi.c
    @@ -719,6 +719,13 @@ void __init efi_systab_report_header(con
    systab_hdr->revision >> 16,
    systab_hdr->revision & 0xffff,
    vendor);
    +
    + if (IS_ENABLED(CONFIG_X86_64) &&
    + systab_hdr->revision > EFI_1_10_SYSTEM_TABLE_REVISION &&
    + !strcmp(vendor, "Apple")) {
    + pr_info("Apple Mac detected, using EFI v1.10 runtime services only\n");
    + efi.runtime_version = EFI_1_10_SYSTEM_TABLE_REVISION;
    + }
    }

    static __initdata char memory_type_name[][13] = {

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