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    Subject[PATCH 4.4 060/342] efi: Add pstore variables to the deletion whitelist
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Matt Fleming <matt@codeblueprint.co.uk>

    commit e246eb568bc4cbbdd8a30a3c11151ff9b7ca7312 upstream.

    Laszlo explains why this is a good idea,

    'This is because the pstore filesystem can be backed by UEFI variables,
    and (for example) a crash might dump the last kilobytes of the dmesg
    into a number of pstore entries, each entry backed by a separate UEFI
    variable in the above GUID namespace, and with a variable name
    according to the above pattern.

    Please see "drivers/firmware/efi/efi-pstore.c".

    While this patch series will not prevent the user from deleting those
    UEFI variables via the pstore filesystem (i.e., deleting a pstore fs
    entry will continue to delete the backing UEFI variable), I think it
    would be nice to preserve the possibility for the sysadmin to delete
    Linux-created UEFI variables that carry portions of the crash log,
    *without* having to mount the pstore filesystem.'

    There's also no chance of causing machines to become bricked by
    deleting these variables, which is the whole purpose of excluding
    things from the whitelist.

    Use the LINUX_EFI_CRASH_GUID guid and a wildcard '*' for the match so
    that we don't have to update the string in the future if new variable
    name formats are created for crash dump variables.

    Reported-by: Laszlo Ersek <lersek@redhat.com>
    Acked-by: Peter Jones <pjones@redhat.com>
    Tested-by: Peter Jones <pjones@redhat.com>
    Cc: Matthew Garrett <mjg59@srcf.ucam.org>
    Cc: "Lee, Chun-Yi" <jlee@suse.com>
    Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/firmware/efi/vars.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/drivers/firmware/efi/vars.c
    +++ b/drivers/firmware/efi/vars.c
    @@ -198,6 +198,7 @@ static const struct variable_validate va
    { EFI_GLOBAL_VARIABLE_GUID, "OsIndications", NULL },
    { EFI_GLOBAL_VARIABLE_GUID, "PlatformLang", validate_ascii_string },
    { EFI_GLOBAL_VARIABLE_GUID, "Timeout", validate_uint16 },
    + { LINUX_EFI_CRASH_GUID, "*", NULL },
    { NULL_GUID, "", NULL },
    };
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