Messages in this thread | | | Date | Fri, 13 May 2022 10:19:17 -0700 | Subject | Re: [PATCH v4] x86/kexec: Carry forward IMA measurement log on kexec | From | Lakshmi Ramasubramanian <> |
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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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