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    Subject[PATCH 05/27] kexec_load: Disable at runtime if the kernel is locked down
    From
    From: Matthew Garrett <mjg59@srcf.ucam.org>

    The kexec_load() syscall permits the loading and execution of arbitrary
    code in ring 0, which is something that lock-down is meant to prevent. It
    makes sense to disable kexec_load() in this situation.

    This does not affect kexec_file_load() syscall which can check for a
    signature on the image to be booted.

    Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Acked-by: Dave Young <dyoung@redhat.com>
    Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
    Reviewed-by: James Morris <james.l.morris@oracle.com>
    cc: kexec@lists.infradead.org
    ---
    kernel/kexec.c | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/kernel/kexec.c b/kernel/kexec.c
    index 68559808fdfa..8ea0ce31271f 100644
    --- a/kernel/kexec.c
    +++ b/kernel/kexec.c
    @@ -207,6 +207,13 @@ static inline int kexec_load_check(unsigned long nr_segments,
    if (result < 0)
    return result;

    + /*
    + * kexec can be used to circumvent module loading restrictions, so
    + * prevent loading in that case
    + */
    + if (kernel_is_locked_down("kexec of unsigned images"))
    + return -EPERM;
    +
    /*
    * Verify we have a legal set of flags
    * This leaves us room for future extensions.
    --
    2.21.0.352.gf09ad66450-goog
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