From 62a03defeabd58f74e07ca030d6c21e069d4d88e Mon Sep 17 00:00:00 2001 From: Chen Yu Date: Thu, 20 Oct 2016 16:14:52 +0800 Subject: [PATCH] PM / hibernate: Verify the consistent of e820 memory map by md5 digest On some platforms, there is occasional panic triggered when trying to resume from hibernation, a typical panic looks like: "BUG: unable to handle kernel paging request at ffff880085894000 IP: [] load_image_lzo+0x8c2/0xe70" Investigation carried out by Lee Chun-Yi shows that this is because e820 map has been changed by BIOS across hibernation, and one of the page frames from suspend kernel is right located in restore kernel's unmapped region, so panic comes out when accessing unmapped kernel address. In order to expose this issue earlier, the md5 hash of e820 map is passed from suspend kernel to restore kernel, and the restore kernel will terminate the resume process once it finds the md5 hash are not the same. As the format of image header has been modified, the magic number should also be adjusted as kernels with the same RESTORE_MAGIC have to use the same header format and interpret all of the fields in it in the same way. If the suspend kernel is built without md5 support, and the restore kernel has md5 support, then the latter will bypass the check process. Vice versa the restore kernel will bypass the check if it does not support md5 operation. Note: 1. Without this patch applied, it is possible that BIOS has provided an inconsistent memory map, but the resume kernel is still able to restore the image anyway(e.g, E820_RAM region is the superset of the previous one), although the system might be unstable. So this patch tries to treat any inconsistent e820 as illegal. 2. Another case is, this patch replies on comparing the e820_saved, but currently the e820_save might not be strictly the same across hibernation, even if BIOS has provided consistent e820 map - In theory mptable might modify the BIOS-provided e820_saved dynamically in early_reserve_e820_mpc_new, which would allocate a buffer from E820_RAM, and marks it from E820_RAM to E820_RESERVED). This is a potential and rare case we need to deal with in OS in the future. Suggested-by: Pavel Machek Suggested-by: Rafael J. Wysocki Signed-off-by: Chen Yu Reviewed-by: Lee, Chun-Yi Acked-by: Pavel Machek Signed-off-by: Rafael J. Wysocki --- arch/x86/power/hibernate_64.c | 94 ++++++++++++++++++++++++++++++++++- 1 file changed, 92 insertions(+), 2 deletions(-) diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c index 9634557a5444..ded2e8272382 100644 --- a/arch/x86/power/hibernate_64.c +++ b/arch/x86/power/hibernate_64.c @@ -11,6 +11,10 @@ #include #include #include +#include +#include + +#include #include #include @@ -177,14 +181,86 @@ int pfn_is_nosave(unsigned long pfn) return (pfn >= nosave_begin_pfn) && (pfn < nosave_end_pfn); } +#define MD5_DIGEST_SIZE 16 + struct restore_data_record { unsigned long jump_address; unsigned long jump_address_phys; unsigned long cr3; unsigned long magic; + u8 e820_digest[MD5_DIGEST_SIZE]; }; -#define RESTORE_MAGIC 0x123456789ABCDEF0UL +#define RESTORE_MAGIC 0x23456789ABCDEF01UL + +#if IS_BUILTIN(CONFIG_CRYPTO_MD5) +/** + * get_e820_md5 - calculate md5 according to given e820 map + * + * @map: the e820 map to be calculated + * @buf: the md5 result to be stored to + */ +static int get_e820_md5(struct e820map *map, void *buf) +{ + struct scatterlist sg; + struct crypto_ahash *tfm; + int size; + int ret = 0; + + tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC); + if (IS_ERR(tfm)) + return -ENOMEM; + + { + AHASH_REQUEST_ON_STACK(req, tfm); + size = offsetof(struct e820map, map) + + sizeof(struct e820entry) * map->nr_map; + ahash_request_set_tfm(req, tfm); + sg_init_one(&sg, (u8 *)map, size); + ahash_request_set_callback(req, 0, NULL, NULL); + ahash_request_set_crypt(req, &sg, buf, size); + + if (crypto_ahash_digest(req)) + ret = -EINVAL; + ahash_request_zero(req); + } + crypto_free_ahash(tfm); + + return ret; +} + +static void hibernation_e820_save(void *buf) +{ + get_e820_md5(e820_saved, buf); +} + +static bool hibernation_e820_mismatch(void *buf) +{ + int ret; + u8 result[MD5_DIGEST_SIZE]; + + memset(result, 0, MD5_DIGEST_SIZE); + /* If there is no digest in suspend kernel, let it go. */ + if (!memcmp(result, buf, MD5_DIGEST_SIZE)) + return false; + + ret = get_e820_md5(e820_saved, result); + if (ret) + return true; + + return memcmp(result, buf, MD5_DIGEST_SIZE) ? true : false; +} +#else +static void hibernation_e820_save(void *buf) +{ +} + +static bool hibernation_e820_mismatch(void *buf) +{ + /* If md5 is not builtin for restore kernel, let it go. */ + return false; +} +#endif /** * arch_hibernation_header_save - populate the architecture specific part @@ -201,6 +277,9 @@ int arch_hibernation_header_save(void *addr, unsigned int max_size) rdr->jump_address_phys = __pa_symbol(&restore_registers); rdr->cr3 = restore_cr3; rdr->magic = RESTORE_MAGIC; + + hibernation_e820_save(rdr->e820_digest); + return 0; } @@ -216,5 +295,16 @@ int arch_hibernation_header_restore(void *addr) restore_jump_address = rdr->jump_address; jump_address_phys = rdr->jump_address_phys; restore_cr3 = rdr->cr3; - return (rdr->magic == RESTORE_MAGIC) ? 0 : -EINVAL; + + if (rdr->magic != RESTORE_MAGIC) { + pr_crit("Unrecognized hibernate image header format!\n"); + return -EINVAL; + } + + if (hibernation_e820_mismatch(rdr->e820_digest)) { + pr_crit("Hibernate inconsistent memory map detected!\n"); + return -ENODEV; + } + + return 0; } -- 2.20.1