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Message-ID: <CAKv+Gu-jPao1zUrZPH3BMqvTrRY9QmXdTNcoG3Y2mpVx3zjL4A@mail.gmail.com>
Date: Fri, 18 Aug 2017 12:48:49 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: Kernel Hardening <kernel-hardening@...ts.openwall.com>
Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, Arnd Bergmann <arnd@...db.de>,
Nicolas Pitre <nico@...aro.org>, Russell King <linux@...linux.org.uk>,
Kees Cook <keescook@...omium.org>, Thomas Garnier <thgarnie@...gle.com>,
Marc Zyngier <marc.zyngier@....com>, Mark Rutland <mark.rutland@....com>,
Tony Lindgren <tony@...mide.com>, Matt Fleming <matt@...eblueprint.co.uk>,
Dave Martin <dave.martin@....com>
Subject: Re: [PATCH 29/30] efi/libstub: arm: reserve bootloader supplied
initrd in memory map
On 14 August 2017 at 13:54, Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> Under KASLR, the EFI stub may allocate the kernel anywhere in the
> physical address space, which could be right on top of an initrd
> if it was supplied by the bootloader (i.e., GRUB) in /chosen rather
> than passed via the initrd= command line option. So allocate the
> pages explicitly, this ensures that the random memory allocation
> routine will disregard the region.
>
> Note that this means that we need to defer the handle_kernel_image()
> call.
>
> Cc: Matt Fleming <matt@...eblueprint.co.uk>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
If nobody objects, I will take this patch through the EFI tree
separately for v4.14, given that it fixes an issue that may affect
arm64 as well.
> ---
> drivers/firmware/efi/libstub/arm-stub.c | 51 ++++++++++++--------
> drivers/firmware/efi/libstub/efistub.h | 3 ++
> drivers/firmware/efi/libstub/fdt.c | 42 ++++++++++++++++
> 3 files changed, 75 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
> index 8181ac179d14..f5ef5ccd5f45 100644
> --- a/drivers/firmware/efi/libstub/arm-stub.c
> +++ b/drivers/firmware/efi/libstub/arm-stub.c
> @@ -133,6 +133,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
> unsigned long reserve_size = 0;
> enum efi_secureboot_mode secure_boot;
> struct screen_info *si;
> + bool have_chosen_initrd;
>
> /* Check if we were booted by the EFI firmware */
> if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
> @@ -183,15 +184,6 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
>
> si = setup_graphics(sys_table);
>
> - status = handle_kernel_image(sys_table, image_addr, &image_size,
> - &reserve_addr,
> - &reserve_size,
> - dram_base, image);
> - if (status != EFI_SUCCESS) {
> - pr_efi_err(sys_table, "Failed to relocate kernel\n");
> - goto fail_free_cmdline;
> - }
> -
> secure_boot = efi_get_secureboot(sys_table);
>
> /*
> @@ -209,7 +201,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
>
> if (status != EFI_SUCCESS) {
> pr_efi_err(sys_table, "Failed to load device tree!\n");
> - goto fail_free_image;
> + goto fail_free_cmdline;
> }
> }
>
> @@ -222,16 +214,33 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
> pr_efi(sys_table, "Using DTB from configuration table\n");
> }
>
> - if (!fdt_addr)
> + if (!fdt_addr) {
> pr_efi(sys_table, "Generating empty DTB\n");
> + have_chosen_initrd = false;
> + } else {
> + status = efi_reserve_dtb_initrd(sys_table, (void *)fdt_addr);
> + have_chosen_initrd = (status != EFI_NOT_FOUND);
> + }
>
> - status = handle_cmdline_files(sys_table, image, cmdline_ptr, "initrd=",
> - efi_get_max_initrd_addr(dram_base,
> - *image_addr),
> - (unsigned long *)&initrd_addr,
> - (unsigned long *)&initrd_size);
> - if (status != EFI_SUCCESS)
> - pr_efi_err(sys_table, "Failed initrd from command line!\n");
> + status = handle_kernel_image(sys_table, image_addr, &image_size,
> + &reserve_addr, &reserve_size,
> + dram_base, image);
> + if (status != EFI_SUCCESS) {
> + pr_efi_err(sys_table, "Failed to relocate kernel\n");
> + goto fail_free_fdt;
> + }
> +
> + if (!have_chosen_initrd) {
> + status = handle_cmdline_files(sys_table, image, cmdline_ptr,
> + "initrd=",
> + efi_get_max_initrd_addr(dram_base,
> + *image_addr),
> + (unsigned long *)&initrd_addr,
> + (unsigned long *)&initrd_size);
> + if (status != EFI_SUCCESS)
> + pr_efi_err(sys_table,
> + "Failed initrd from command line!\n");
> + }
>
> efi_random_get_seed(sys_table);
>
> @@ -272,11 +281,11 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
> pr_efi_err(sys_table, "Failed to update FDT and exit boot services\n");
>
> efi_free(sys_table, initrd_size, initrd_addr);
> - efi_free(sys_table, fdt_size, fdt_addr);
> -
> -fail_free_image:
> efi_free(sys_table, image_size, *image_addr);
> efi_free(sys_table, reserve_size, reserve_addr);
> +
> +fail_free_fdt:
> + efi_free(sys_table, fdt_size, fdt_addr);
> fail_free_cmdline:
> free_screen_info(sys_table, si);
> efi_free(sys_table, cmdline_size, (unsigned long)cmdline_ptr);
> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> index aaf2aeb785ea..35b514d7d962 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -68,4 +68,7 @@ efi_status_t check_platform_features(efi_system_table_t *sys_table_arg);
>
> efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg);
>
> +efi_status_t efi_reserve_dtb_initrd(efi_system_table_t *sys_table_arg,
> + const void *fdt);
> +
> #endif
> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> index 8830fa601e45..54408c95e094 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -385,3 +385,45 @@ void *get_fdt(efi_system_table_t *sys_table, unsigned long *fdt_size)
>
> return fdt;
> }
> +
> +efi_status_t efi_reserve_dtb_initrd(efi_system_table_t *sys_table_arg,
> + const void *fdt)
> +{
> + int chosen, len;
> + const void *prop;
> + efi_physical_addr_t start, end;
> + unsigned long num_pages;
> + efi_status_t status;
> +
> + chosen = fdt_path_offset(fdt, "/chosen");
> + if (chosen == -FDT_ERR_NOTFOUND)
> + return EFI_NOT_FOUND;
> +
> + prop = fdt_getprop(fdt, chosen, "linux,initrd-start", &len);
> + if (!prop)
> + return EFI_NOT_FOUND;
> +
> + start = (len == sizeof(fdt32_t)) ? fdt32_to_cpu(*(fdt32_t *)prop)
> + : fdt64_to_cpu(*(fdt64_t *)prop);
> +
> + prop = fdt_getprop(fdt, chosen, "linux,initrd-end", &len);
> + if (!prop)
> + return EFI_NOT_FOUND;
> +
> + end = (len == sizeof(fdt32_t)) ? fdt32_to_cpu(*(fdt32_t *)prop)
> + : fdt64_to_cpu(*(fdt64_t *)prop);
> +
> + start = round_down(start, EFI_PAGE_SIZE);
> + num_pages = round_up(end - start, EFI_PAGE_SIZE) / EFI_PAGE_SIZE;
> +
> + status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
> + EFI_LOADER_DATA, num_pages, &start);
> +
> + if (status != EFI_SUCCESS)
> + pr_efi_err(sys_table_arg,
> + "Failed to reserve initrd area found in /chosen\n");
> + else
> + pr_efi(sys_table_arg, "Using initrd found in /chosen\n");
> +
> + return status;
> +}
> --
> 2.11.0
>
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