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Subject[PATCH V2 0/2] kexec: refactor CONFIG_KEXEC/CONFIG_KEXEC_FILE Kconfig
Previously Theodore Ts'o brought up an issue about kexec_load syscall bypassing
signature verification:
https://lkml.org/lkml/2015/6/14/280

Because we have two kexec load syscall, one kexec_load, another kexec_file_load,
the latter one was introduced by Vivek Goyal, it is mainly for supporting UEFI
secure boot. kexec_file_load verifies kernel signature, but even if with
CONFIG_KEXEC_VERIFY_SIG=y and CONFIG_KEXEC_FILE=y, kexec-tools still can use
old syscall and bypass signature verification.

KEXEC_FILE can also be used without UEFI, so kexec can always verify kernel
signature for security purpose.

The suggestion in above thread is add a new Kconfig option for kexec common
code, here I use KEXEC_CORE, KEXEC and KEXEC_FILE select KEXEC_CORE so one can
compile only KEXEC_FILE without old kexec_load syscall.

There's checkpatch warnings and errors, I would like to send furthuer cleanup
patches after this series. Please let me know if you have other suggestions.
checkpatch errors are for cases such as assign a value to static variables.

Changes to V1:
* drop patch 3/3 which is not belonging to this series
* move KEXEC_CORE to generic arch/Kconfig, arch KEXEC selects KEXEC_CORE
* add KEXEC_CORE in s390 arch.

Tested kexec_load only, kexec_file_load only, kexec and kexec_file_load built in cases in x86. For kexec_file_load, tested signed and un-signed kernel.
Tested kexec_load in powerpc64 arch.
Build tested arm arch.

For kexec_file_load, if you do not specify "-s" in kexec-tools, kexec load
will hang, though "-s" is mandatory for kexec_file_load, kexec should still
fail out instead of hanging there, here is a fix in kexec-tools:

--- kexec-tools.orig/kexec/crashdump-elf.c
+++ kexec-tools/kexec/crashdump-elf.c
@@ -145,11 +145,12 @@ int FUNC(struct kexec_info *info,

count_cpu = nr_cpus;
for (i = 0; count_cpu > 0; i++) {
- if (get_note_info(i, &notes_addr, &notes_len) < 0) {
- /* This cpu is not present. Skip it. */
- continue;
- }
+ int ret;
+
+ ret = get_note_info(i, &notes_addr, &notes_len);
count_cpu--;
+ if (ret < 0) /* This cpu is not present. Skip it. */
+ continue;

phdr = (PHDR *) bufp;
bufp += sizeof(PHDR);
Below is the diffstat of the patche series:
--
arch/Kconfig | 3
arch/arm/Kconfig | 1
arch/ia64/Kconfig | 1
arch/m68k/Kconfig | 1
arch/mips/Kconfig | 1
arch/powerpc/Kconfig | 1
arch/s390/Kconfig | 1
arch/sh/Kconfig | 1
arch/tile/Kconfig | 1
arch/x86/Kconfig | 3
arch/x86/boot/header.S | 2
arch/x86/include/asm/kdebug.h | 2
arch/x86/kernel/Makefile | 4
arch/x86/kernel/kvmclock.c | 4
arch/x86/kernel/reboot.c | 4
arch/x86/kernel/setup.c | 2
arch/x86/kernel/vmlinux.lds.S | 2
arch/x86/kvm/vmx.c | 8
arch/x86/platform/efi/efi.c | 4
arch/x86/platform/uv/uv_nmi.c | 6
drivers/firmware/efi/Kconfig | 2
drivers/pci/pci-driver.c | 2
include/linux/kexec.h | 12
init/initramfs.c | 4
kernel/Makefile | 2
kernel/events/core.c | 2
kernel/kexec.c | 2633 ------------------------------------------
kernel/kexec_core.c | 1594 +++++++++++++++++++++++++
kernel/kexec_file.c | 1044 ++++++++++++++++
kernel/kexec_internal.h | 22
kernel/ksysfs.c | 6
kernel/printk/printk.c | 2
kernel/reboot.c | 2
kernel/sysctl.c | 2
34 files changed, 2725 insertions(+), 2656 deletions(-)
--
Thanks
Dave



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