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    SubjectRe: [PATCH v4] x86/kexec: Carry forward IMA measurement log on kexec
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    Hi Jonathan,

    On 5/12/2022 9:25 AM, Jonathan McDowell wrote:
    > On kexec file load Integrity Measurement Architecture (IMA) subsystem
    > may verify the IMA signature of the kernel and initramfs, and measure
    > it. The command line parameters passed to the kernel in the kexec call
    > may also be measured by IMA. A remote attestation service can verify
    > a TPM quote based on the TPM event log, the IMA measurement list, and
    > the TPM PCR data. This can be achieved only if the IMA measurement log
    > is carried over from the current kernel to the next kernel across
    > the kexec call.
    >
    > powerpc and ARM64 both achieve this using device tree with a
    > "linux,ima-kexec-buffer" node. x86 platforms generally don't make use of
    > device tree, so use the setup_data mechanism to pass the IMA buffer to
    > the new kernel.
    >
    > Signed-off-by: Jonathan McDowell <noodles@fb.com>
    > ---
    > v4:
    > - Guard ima.h function prototypes with CONFIG_HAVE_IMA_KEXEC
    > v3:
    > - Rebase on tip/master
    > - Pull ima_(free|get)_kexec_buffer into x86 code
    > - Push ifdefs into functions where possible
    > - Reverse fir tree variable declarations
    > - Fix section annotation on ima_free_kexec_buffer (__meminit)
    > - Only allocate ima_setup_data space when IMA_KEXEC is enabled
    > v2:
    > - Fix operation with EFI systems
    > ---
    > arch/x86/Kconfig | 1 +
    > arch/x86/include/uapi/asm/bootparam.h | 9 ++++
    > arch/x86/kernel/e820.c | 6 +--
    > arch/x86/kernel/kexec-bzimage64.c | 38 ++++++++++++++++
    > arch/x86/kernel/setup.c | 62 +++++++++++++++++++++++++++
    > drivers/of/kexec.c | 1 +
    > include/linux/ima.h | 5 +++
    > include/linux/of.h | 2 -
    > security/integrity/ima/ima_kexec.c | 2 +-
    > 9 files changed, 120 insertions(+), 6 deletions(-)
    >
    > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    > index f1320d9a3da3..594636f02da4 100644
    > --- a/arch/x86/Kconfig
    > +++ b/arch/x86/Kconfig
    > @@ -2027,6 +2027,7 @@ config KEXEC_FILE
    > bool "kexec file based system call"
    > select KEXEC_CORE
    > select BUILD_BIN2C
    > + select HAVE_IMA_KEXEC if IMA
    > depends on X86_64
    > depends on CRYPTO=y
    > depends on CRYPTO_SHA256=y
    > diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
    > index bea5cdcdf532..ca0796ac4403 100644
    > --- a/arch/x86/include/uapi/asm/bootparam.h
    > +++ b/arch/x86/include/uapi/asm/bootparam.h
    > @@ -11,6 +11,7 @@
    > #define SETUP_APPLE_PROPERTIES 5
    > #define SETUP_JAILHOUSE 6
    > #define SETUP_CC_BLOB 7
    > +#define SETUP_IMA 8
    >
    > #define SETUP_INDIRECT (1<<31)
    >
    > @@ -172,6 +173,14 @@ struct jailhouse_setup_data {
    > } __attribute__((packed)) v2;
    > } __attribute__((packed));
    >
    > +/*
    > + * IMA buffer setup data information from the previous kernel during kexec
    > + */
    > +struct ima_setup_data {
    > + __u64 addr;
    > + __u64 size;
    > +} __attribute__((packed));
    > +
    > /* The so-called "zeropage" */
    > struct boot_params {
    > struct screen_info screen_info; /* 0x000 */
    > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
    > index f267205f2d5a..9dac24680ff8 100644
    > --- a/arch/x86/kernel/e820.c
    > +++ b/arch/x86/kernel/e820.c
    > @@ -1017,10 +1017,10 @@ void __init e820__reserve_setup_data(void)
    > e820__range_update(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
    >
    > /*
    > - * SETUP_EFI is supplied by kexec and does not need to be
    > - * reserved.
    > + * SETUP_EFI and SETUP_IMA are supplied by kexec and do not need
    > + * to be reserved.
    > */
    > - if (data->type != SETUP_EFI)
    > + if (data->type != SETUP_EFI && data->type != SETUP_IMA)
    > e820__range_update_kexec(pa_data,
    > sizeof(*data) + data->len,
    > E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
    > diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
    > index 170d0fd68b1f..54bd4ce5f908 100644
    > --- a/arch/x86/kernel/kexec-bzimage64.c
    > +++ b/arch/x86/kernel/kexec-bzimage64.c
    > @@ -186,6 +186,33 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
    > }
    > #endif /* CONFIG_EFI */
    >
    > +static void
    > +setup_ima_state(const struct kimage *image, struct boot_params *params,
    > + unsigned long params_load_addr,
    > + unsigned int ima_setup_data_offset)
    > +{
    > +#ifdef CONFIG_IMA_KEXEC
    > + struct setup_data *sd = (void *)params + ima_setup_data_offset;
    > + unsigned long setup_data_phys;
    > + struct ima_setup_data *ima;
    > +
    > + if (!image->ima_buffer_size)
    > + return;
    > +
    > + sd->type = SETUP_IMA;
    > + sd->len = sizeof(*ima);
    > +
    > + ima = (void *)sd + sizeof(struct setup_data);
    > + ima->addr = image->ima_buffer_addr;
    > + ima->size = image->ima_buffer_size;
    > +
    > + /* Add setup data */
    > + setup_data_phys = params_load_addr + ima_setup_data_offset;
    > + sd->next = params->hdr.setup_data;
    > + params->hdr.setup_data = setup_data_phys;
    > +#endif /* CONFIG_IMA_KEXEC */
    > +}
    > +
    > static int
    > setup_boot_parameters(struct kimage *image, struct boot_params *params,
    > unsigned long params_load_addr,
    > @@ -247,6 +274,13 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
    > setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
    > efi_setup_data_offset);
    > #endif
    > +
    > + /* Setup IMA log buffer state */
    > + setup_ima_state(image, params, params_load_addr,
    > + efi_setup_data_offset +
    > + sizeof(struct setup_data) +
    > + sizeof(struct efi_setup_data));
    Here you could check image->ima_buffer_size and call setup_ima_state()
    only if it is non-zero.

    > +
    > /* Setup EDD info */
    > memcpy(params->eddbuf, boot_params.eddbuf,
    > EDDMAXNR * sizeof(struct edd_info));
    > @@ -403,6 +437,10 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
    > sizeof(struct setup_data) +
    > sizeof(struct efi_setup_data);
    >
    > + if (IS_ENABLED(CONFIG_IMA_KEXEC))
    > + kbuf.bufsz += sizeof(struct setup_data) +
    > + sizeof(struct ima_setup_data);
    > +
    > params = kzalloc(kbuf.bufsz, GFP_KERNEL);
    > if (!params)
    > return ERR_PTR(-ENOMEM);
    > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
    > index 249981bf3d8a..ab5e7a351845 100644
    > --- a/arch/x86/kernel/setup.c
    > +++ b/arch/x86/kernel/setup.c
    > @@ -11,6 +11,7 @@
    > #include <linux/dma-map-ops.h>
    > #include <linux/dmi.h>
    > #include <linux/efi.h>
    > +#include <linux/ima.h>
    > #include <linux/init_ohci1394_dma.h>
    > #include <linux/initrd.h>
    > #include <linux/iscsi_ibft.h>
    > @@ -145,6 +146,11 @@ __visible unsigned long mmu_cr4_features __ro_after_init;
    > __visible unsigned long mmu_cr4_features __ro_after_init = X86_CR4_PAE;
    > #endif
    >
    > +#ifdef CONFIG_IMA
    > +static phys_addr_t ima_kexec_buffer_phys;
    > +static size_t ima_kexec_buffer_size;
    > +#endif
    > +
    > /* Boot loader ID and version as integers, for the benefit of proc_dointvec */
    > int bootloader_type, bootloader_version;
    >
    > @@ -335,6 +341,59 @@ static void __init reserve_initrd(void)
    > }
    > #endif /* CONFIG_BLK_DEV_INITRD */
    >
    > +static void __init add_early_ima_buffer(u64 phys_addr)
    > +{
    > +#ifdef CONFIG_IMA
    > + struct ima_setup_data *data;
    > +
    > + data = early_memremap(phys_addr + sizeof(struct setup_data),
    > + sizeof(*data));
    > + if (!data) {
    > + pr_warn("setup: failed to memremap ima_setup_data entry\n");
    > + return;
    > + }
    Here if memory allocation fails, would kexec system call fail or would
    it only not add IMA buffer, but continue with the system call?

    > + if (data->size != 0) {
    > + memblock_reserve(data->addr, data->size);
    > + ima_kexec_buffer_phys = data->addr;
    > + ima_kexec_buffer_size = data->size;
    > + }
    > + early_memunmap(data, sizeof(*data));
    > +#else
    > + pr_warn("Passed IMA kexec data, but CONFIG_IMA not set. Ignoring.\n");
    Is this warning message useful? Can we just inline (NOP) this function
    if CONFIG_IMA is not set?

    > +#endif
    > +}
    > +
    > +#if defined(CONFIG_IMA) && !defined(CONFIG_OF_FLATTREE)
    > +int __meminit ima_free_kexec_buffer(void)
    > +{
    ima_free_kexec_buffer() should be invoked if the previous kernel had
    passed the IMA buffer (i.e., CONFIG_HAVE_IMA_KEXEC is set).
    CONFIG_HAVE_IMA_KEXEC would be set only if CONFIG_IMA is set. Is the
    above check still required?

    thanks,
    -lakshmi

    > + int rc;
    > +
    > + if (ima_kexec_buffer_size == 0)
    > + return -ENOENT;
    > +
    > + rc = memblock_phys_free(ima_kexec_buffer_phys,
    > + ima_kexec_buffer_size);
    > + if (rc)
    > + return rc;
    > +
    > + ima_kexec_buffer_phys = 0;
    > + ima_kexec_buffer_size = 0;
    > +
    > + return 0;
    > +}
    > +
    > +int __init ima_get_kexec_buffer(void **addr, size_t *size)
    > +{
    > + if (ima_kexec_buffer_size == 0)
    > + return -ENOENT;
    > +
    > + *addr = __va(ima_kexec_buffer_phys);
    > + *size = ima_kexec_buffer_size;
    > +
    > + return 0;
    > +}
    > +#endif
    > +
    > static void __init parse_setup_data(void)
    > {
    > struct setup_data *data;
    > @@ -360,6 +419,9 @@ static void __init parse_setup_data(void)
    > case SETUP_EFI:
    > parse_efi_setup(pa_data, data_len);
    > break;
    > + case SETUP_IMA:
    > + add_early_ima_buffer(pa_data);
    > + break;
    > default:
    > break;
    > }
    > diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
    > index b9bd1cff1793..74fdd490f7c0 100644
    > --- a/drivers/of/kexec.c
    > +++ b/drivers/of/kexec.c
    > @@ -9,6 +9,7 @@
    > * Copyright (C) 2016 IBM Corporation
    > */
    >
    > +#include <linux/ima.h>
    > #include <linux/kernel.h>
    > #include <linux/kexec.h>
    > #include <linux/memblock.h>
    > diff --git a/include/linux/ima.h b/include/linux/ima.h
    > index 426b1744215e..ff4bd993e432 100644
    > --- a/include/linux/ima.h
    > +++ b/include/linux/ima.h
    > @@ -140,6 +140,11 @@ static inline int ima_measure_critical_data(const char *event_label,
    >
    > #endif /* CONFIG_IMA */
    >
    > +#ifdef CONFIG_HAVE_IMA_KEXEC
    > +int ima_free_kexec_buffer(void);
    > +int ima_get_kexec_buffer(void **addr, size_t *size);
    > +#endif
    > +
    > #ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT
    > extern bool arch_ima_get_secureboot(void);
    > extern const char * const *arch_get_ima_policy(void);
    > diff --git a/include/linux/of.h b/include/linux/of.h
    > index 04971e85fbc9..c2f58d2e3a0e 100644
    > --- a/include/linux/of.h
    > +++ b/include/linux/of.h
    > @@ -441,8 +441,6 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
    > unsigned long initrd_load_addr,
    > unsigned long initrd_len,
    > const char *cmdline, size_t extra_fdt_size);
    > -int ima_get_kexec_buffer(void **addr, size_t *size);
    > -int ima_free_kexec_buffer(void);
    > #else /* CONFIG_OF */
    >
    > static inline void of_core_init(void)
    > diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
    > index 13753136f03f..419dc405c831 100644
    > --- a/security/integrity/ima/ima_kexec.c
    > +++ b/security/integrity/ima/ima_kexec.c
    > @@ -137,7 +137,7 @@ void ima_add_kexec_buffer(struct kimage *image)
    > /*
    > * Restore the measurement list from the previous kernel.
    > */
    > -void ima_load_kexec_buffer(void)
    > +void __init ima_load_kexec_buffer(void)
    > {
    > void *kexec_buffer = NULL;
    > size_t kexec_buffer_size = 0;

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