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R. Silva" , linux-hardening@vger.kernel.org (open list:KERNEL HARDENING (not covered by other areas):Keyword:\b__counted_by\b) Subject: [PATCH v4 2/7] crash_dump: make dm crypt keys persist for the kdump kernel Date: Thu, 23 May 2024 13:04:43 +0800 Message-ID: <20240523050451.788754-3-coxu@redhat.com> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20240523050451.788754-1-coxu@redhat.com> References: <20240523050451.788754-1-coxu@redhat.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com A sysfs /sys/kernel/crash_dm_crypt_keys is provided for user space to make the dm crypt keys persist for the kdump kernel. User space can send the following commands, - "init KEY_NUM" Initialize needed structures - "record KEY_DESC" Record a key description. The key must be a logon key. User space can also read this API to learn about current state. Signed-off-by: Coiby Xu --- include/linux/crash_core.h | 5 +- kernel/Kconfig.kexec | 8 +++ kernel/Makefile | 1 + kernel/crash_dump_dm_crypt.c | 113 +++++++++++++++++++++++++++++++++++ kernel/ksysfs.c | 22 +++++++ 5 files changed, 148 insertions(+), 1 deletion(-) create mode 100644 kernel/crash_dump_dm_crypt.c diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h index 44305336314e..6bff1c24efa3 100644 --- a/include/linux/crash_core.h +++ b/include/linux/crash_core.h @@ -34,7 +34,10 @@ static inline void arch_kexec_protect_crashkres(void) { } static inline void arch_kexec_unprotect_crashkres(void) { } #endif - +#ifdef CONFIG_CRASH_DM_CRYPT +int crash_sysfs_dm_crypt_keys_read(char *buf); +int crash_sysfs_dm_crypt_keys_write(const char *buf, size_t count); +#endif #ifndef arch_crash_handle_hotplug_event static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { } diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec index 6c34e63c88ff..88525ad1c80a 100644 --- a/kernel/Kconfig.kexec +++ b/kernel/Kconfig.kexec @@ -116,6 +116,14 @@ config CRASH_DUMP For s390, this option also enables zfcpdump. See also +config CRASH_DM_CRYPT + bool "Support saving crash dump to dm-crypt encrypted volume" + depends on CRASH_DUMP + help + With this option enabled, user space can intereact with + /sys/kernel/crash_dm_crypt_keys to make the dm crypt keys + persistent for the crash dump kernel. + config CRASH_HOTPLUG bool "Update the crash elfcorehdr on system configuration changes" default y diff --git a/kernel/Makefile b/kernel/Makefile index 3c13240dfc9f..f2e5b3e86d12 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -72,6 +72,7 @@ obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o elfcorehdr.o obj-$(CONFIG_CRASH_RESERVE) += crash_reserve.o obj-$(CONFIG_KEXEC_CORE) += kexec_core.o obj-$(CONFIG_CRASH_DUMP) += crash_core.o +obj-$(CONFIG_CRASH_DM_CRYPT) += crash_dump_dm_crypt.o obj-$(CONFIG_KEXEC) += kexec.o obj-$(CONFIG_KEXEC_FILE) += kexec_file.o obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c new file mode 100644 index 000000000000..78809189084a --- /dev/null +++ b/kernel/crash_dump_dm_crypt.c @@ -0,0 +1,113 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include + +#define KEY_NUM_MAX 128 +#define KEY_SIZE_MAX 256 + +// The key scription has the format: cryptsetup:UUID 11+36+1(NULL)=48 +#define KEY_DESC_LEN 48 + +static char *STATE_STR[] = {"fresh", "initialized", "recorded", "loaded"}; +static enum STATE_ENUM { + FRESH = 0, + INITIALIZED, + RECORDED, + LOADED, +} state; + +static unsigned int key_count; +static size_t keys_header_size; + +struct dm_crypt_key { + unsigned int key_size; + char key_desc[KEY_DESC_LEN]; + u8 data[KEY_SIZE_MAX]; +}; + +static struct keys_header { + unsigned int key_count; + struct dm_crypt_key keys[] __counted_by(key_count); +} *keys_header; + +static size_t get_keys_header_size(struct keys_header *keys_header, + size_t key_count) +{ + return struct_size(keys_header, keys, key_count); +} + +static int init(const char *buf) +{ + unsigned int total_keys; + char dummy[5]; + + if (sscanf(buf, "%4s %u", dummy, &total_keys) != 2) + return -EINVAL; + + if (key_count > KEY_NUM_MAX) { + pr_err("Exceed the maximum number of keys (KEY_NUM_MAX=%u)\n", + KEY_NUM_MAX); + return -EINVAL; + } + + keys_header_size = get_keys_header_size(keys_header, total_keys); + key_count = 0; + + keys_header = kzalloc(keys_header_size, GFP_KERNEL); + if (!keys_header) + return -ENOMEM; + + keys_header->key_count = total_keys; + state = INITIALIZED; + return 0; +} + +static int record_key_desc(const char *buf, struct dm_crypt_key *dm_key) +{ + char key_desc[KEY_DESC_LEN]; + char dummy[7]; + + if (state != INITIALIZED) + pr_err("Please send the cmd 'init ' first\n"); + + if (sscanf(buf, "%6s %s", dummy, key_desc) != 2) + return -EINVAL; + + if (key_count >= keys_header->key_count) { + pr_warn("Already have %u keys", key_count); + return -EINVAL; + } + + strscpy(dm_key->key_desc, key_desc, KEY_DESC_LEN); + pr_debug("Key%d (%s) recorded\n", key_count, dm_key->key_desc); + key_count++; + + if (key_count == keys_header->key_count) + state = RECORDED; + + return 0; +} + +static int process_cmd(const char *buf, size_t count) +{ + if (strncmp(buf, "init ", 5) == 0) + return init(buf); + else if (strncmp(buf, "record ", 7) == 0) + return record_key_desc(buf, &keys_header->keys[key_count]); + + return -EINVAL; +} + +int crash_sysfs_dm_crypt_keys_write(const char *buf, size_t count) +{ + if (!is_kdump_kernel()) + return process_cmd(buf, count); + return -EINVAL; +} +EXPORT_SYMBOL(crash_sysfs_dm_crypt_keys_write); + +int crash_sysfs_dm_crypt_keys_read(char *buf) +{ + return sprintf(buf, "%s\n", STATE_STR[state]); +} +EXPORT_SYMBOL(crash_sysfs_dm_crypt_keys_read); diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 07fb5987b42b..2ba4dcbf5816 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -167,6 +167,25 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj, } KERNEL_ATTR_RO(vmcoreinfo); +#ifdef CONFIG_CRASH_DM_CRYPT +static ssize_t crash_dm_crypt_keys_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return crash_sysfs_dm_crypt_keys_read(buf); +} + +static ssize_t crash_dm_crypt_keys_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int ret; + + ret = crash_sysfs_dm_crypt_keys_write(buf, count); + return ret < 0 ? ret : count; +} +KERNEL_ATTR_RW(crash_dm_crypt_keys); +#endif /* CONFIG_CRASH_DM_CRYPT */ + #ifdef CONFIG_CRASH_HOTPLUG static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -271,6 +290,9 @@ static struct attribute * kernel_attrs[] = { #endif #ifdef CONFIG_VMCORE_INFO &vmcoreinfo_attr.attr, +#ifdef CONFIG_CRASH_DM_CRYPT + &crash_dm_crypt_keys_attr.attr, +#endif #ifdef CONFIG_CRASH_HOTPLUG &crash_elfcorehdr_size_attr.attr, #endif