Files
linux/kernel/Makefile
Coiby Xu 180cf31af7 crash_dump: make dm crypt keys persist for the kdump kernel
A configfs /sys/kernel/config/crash_dm_crypt_keys is provided for user
space to make the dm crypt keys persist for the kdump kernel.  Take the
case of dumping to a LUKS-encrypted target as an example, here is the life
cycle of the kdump copies of LUKS volume keys,

 1. After the 1st kernel loads the initramfs during boot, systemd uses
    an user-input passphrase to de-crypt the LUKS volume keys or simply
    TPM-sealed volume keys and then save the volume keys to specified
    keyring (using the --link-vk-to-keyring API) and the keys will expire
    within specified time.

 2. A user space tool (kdump initramfs loader like kdump-utils) create
    key items inside /sys/kernel/config/crash_dm_crypt_keys to inform
    the 1st kernel which keys are needed.

 3. When the kdump initramfs is loaded by the kexec_file_load
    syscall, the 1st kernel will iterate created key items, save the
    keys to kdump reserved memory.

 4. When the 1st kernel crashes and the kdump initramfs is booted, the
    kdump initramfs asks the kdump kernel to create a user key using the
    key stored in kdump reserved memory by writing yes to
    /sys/kernel/crash_dm_crypt_keys/restore. Then the LUKS encrypted
    device is unlocked with libcryptsetup's --volume-key-keyring API.

 5. The system gets rebooted to the 1st kernel after dumping vmcore to
    the LUKS encrypted device is finished

Eventually the keys have to stay in the kdump reserved memory for the
kdump kernel to unlock encrypted volumes.  During this process, some
measures like letting the keys expire within specified time are desirable
to reduce security risk.

This patch assumes,
1) there are 128 LUKS devices at maximum to be unlocked thus
   MAX_KEY_NUM=128.

2) a key description won't exceed 128 bytes thus KEY_DESC_MAX_LEN=128.

And here is a demo on how to interact with
/sys/kernel/config/crash_dm_crypt_keys,

    # Add key #1
    mkdir /sys/kernel/config/crash_dm_crypt_keys/7d26b7b4-e342-4d2d-b660-7426b0996720
    # Add key #1's description
    echo cryptsetup:7d26b7b4-e342-4d2d-b660-7426b0996720 > /sys/kernel/config/crash_dm_crypt_keys/description

    # how many keys do we have now?
    cat /sys/kernel/config/crash_dm_crypt_keys/count
    1

    # Add key# 2 in the same way

    # how many keys do we have now?
    cat /sys/kernel/config/crash_dm_crypt_keys/count
    2

    # the tree structure of /crash_dm_crypt_keys configfs
    tree /sys/kernel/config/crash_dm_crypt_keys/
    /sys/kernel/config/crash_dm_crypt_keys/
    ├── 7d26b7b4-e342-4d2d-b660-7426b0996720
    │   └── description
    ├── count
    ├── fce2cd38-4d59-4317-8ce2-1fd24d52c46a
    │   └── description

Link: https://lkml.kernel.org/r/20250502011246.99238-3-coxu@redhat.com
Signed-off-by: Coiby Xu <coxu@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jan Pazdziora <jpazdziora@redhat.com>
Cc: Liu Pingfan <kernelfans@gmail.com>
Cc: Milan Broz <gmazyland@gmail.com>
Cc: Ondrej Kozina <okozina@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-05-21 10:48:20 -07:00

168 lines
5.5 KiB
Makefile

# SPDX-License-Identifier: GPL-2.0
#
# Makefile for the linux kernel.
#
obj-y = fork.o exec_domain.o panic.o \
cpu.o exit.o softirq.o resource.o \
sysctl.o capability.o ptrace.o user.o \
signal.o sys.o umh.o workqueue.o pid.o task_work.o \
extable.o params.o \
kthread.o sys_ni.o nsproxy.o \
notifier.o ksysfs.o cred.o reboot.o \
async.o range.o smpboot.o ucount.o regset.o ksyms_common.o
obj-$(CONFIG_USERMODE_DRIVER) += usermode_driver.o
obj-$(CONFIG_MULTIUSER) += groups.o
obj-$(CONFIG_VHOST_TASK) += vhost_task.o
ifdef CONFIG_FUNCTION_TRACER
# Do not trace internal ftrace files
CFLAGS_REMOVE_irq_work.o = $(CC_FLAGS_FTRACE)
endif
# Branch profiling isn't noinstr-safe
ifdef CONFIG_TRACE_BRANCH_PROFILING
CFLAGS_context_tracking.o += -DDISABLE_BRANCH_PROFILING
endif
# Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip()
# in coverage traces.
KCOV_INSTRUMENT_softirq.o := n
# Avoid KCSAN instrumentation in softirq ("No shared variables, all the data
# are CPU local" => assume no data races), to reduce overhead in interrupts.
KCSAN_SANITIZE_softirq.o = n
# These are called from save_stack_trace() on slub debug path,
# and produce insane amounts of uninteresting coverage.
KCOV_INSTRUMENT_extable.o := n
KCOV_INSTRUMENT_stacktrace.o := n
# Don't self-instrument.
KCOV_INSTRUMENT_kcov.o := n
# If sanitizers detect any issues in kcov, it may lead to recursion
# via printk, etc.
KASAN_SANITIZE_kcov.o := n
KCSAN_SANITIZE_kcov.o := n
UBSAN_SANITIZE_kcov.o := n
KMSAN_SANITIZE_kcov.o := n
CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
obj-y += sched/
obj-y += locking/
obj-y += power/
obj-y += printk/
obj-y += irq/
obj-y += rcu/
obj-y += livepatch/
obj-y += dma/
obj-y += entry/
obj-$(CONFIG_MODULES) += module/
obj-$(CONFIG_KCMP) += kcmp.o
obj-$(CONFIG_FREEZER) += freezer.o
obj-$(CONFIG_PROFILING) += profile.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-y += time/
obj-$(CONFIG_FUTEX) += futex/
obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
obj-$(CONFIG_SMP) += smp.o
ifneq ($(CONFIG_SMP),y)
obj-y += up.o
endif
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
obj-$(CONFIG_KALLSYMS) += kallsyms.o
obj-$(CONFIG_KALLSYMS_SELFTEST) += kallsyms_selftest.o
obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o elfcorehdr.o
obj-$(CONFIG_CRASH_RESERVE) += crash_reserve.o
obj-$(CONFIG_KEXEC_CORE) += kexec_core.o
obj-$(CONFIG_CRASH_DUMP) += crash_core.o
obj-$(CONFIG_CRASH_DM_CRYPT) += crash_dump_dm_crypt.o
obj-$(CONFIG_KEXEC) += kexec.o
obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup/
obj-$(CONFIG_UTS_NS) += utsname.o
obj-$(CONFIG_USER_NS) += user_namespace.o
obj-$(CONFIG_PID_NS) += pid_namespace.o
obj-$(CONFIG_IKCONFIG) += configs.o
obj-$(CONFIG_IKHEADERS) += kheaders.o
obj-$(CONFIG_SMP) += stop_machine.o
obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
obj-$(CONFIG_AUDITSYSCALL) += auditsc.o audit_watch.o audit_fsnotify.o audit_tree.o
obj-$(CONFIG_GCOV_KERNEL) += gcov/
obj-$(CONFIG_KCOV) += kcov.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_FAIL_FUNCTION) += fail_function.o
obj-$(CONFIG_KGDB) += debug/
obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
obj-$(CONFIG_LOCKUP_DETECTOR) += watchdog.o
obj-$(CONFIG_HARDLOCKUP_DETECTOR_BUDDY) += watchdog_buddy.o
obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_perf.o
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
obj-$(CONFIG_LATENCYTOP) += latencytop.o
obj-$(CONFIG_FUNCTION_TRACER) += trace/
obj-$(CONFIG_TRACING) += trace/
obj-$(CONFIG_TRACE_CLOCK) += trace/
obj-$(CONFIG_RING_BUFFER) += trace/
obj-$(CONFIG_TRACEPOINTS) += trace/
obj-$(CONFIG_RETHOOK) += trace/
obj-$(CONFIG_IRQ_WORK) += irq_work.o
obj-$(CONFIG_CPU_PM) += cpu_pm.o
obj-$(CONFIG_BPF) += bpf/
obj-$(CONFIG_KCSAN) += kcsan/
obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
obj-$(CONFIG_CFI_CLANG) += cfi.o
obj-$(CONFIG_PERF_EVENTS) += events/
obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
obj-$(CONFIG_PADATA) += padata.o
obj-$(CONFIG_JUMP_LABEL) += jump_label.o
obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
obj-$(CONFIG_TORTURE_TEST) += torture.o
obj-$(CONFIG_HAS_IOMEM) += iomem.o
obj-$(CONFIG_RSEQ) += rseq.o
obj-$(CONFIG_WATCH_QUEUE) += watch_queue.o
obj-$(CONFIG_RESOURCE_KUNIT_TEST) += resource_kunit.o
obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o
CFLAGS_stackleak.o += $(DISABLE_STACKLEAK_PLUGIN)
obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o
KASAN_SANITIZE_stackleak.o := n
KCSAN_SANITIZE_stackleak.o := n
KCOV_INSTRUMENT_stackleak.o := n
obj-$(CONFIG_SCF_TORTURE_TEST) += scftorture.o
$(obj)/configs.o: $(obj)/config_data.gz
targets += config_data config_data.gz
$(obj)/config_data.gz: $(obj)/config_data FORCE
$(call if_changed,gzip)
filechk_cat = cat $<
$(obj)/config_data: $(KCONFIG_CONFIG) FORCE
$(call filechk,cat)
$(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz
quiet_cmd_genikh = CHK $(obj)/kheaders_data.tar.xz
cmd_genikh = $(CONFIG_SHELL) $(srctree)/kernel/gen_kheaders.sh $@
$(obj)/kheaders_data.tar.xz: FORCE
$(call cmd,genikh)
clean-files := kheaders_data.tar.xz kheaders.md5