[PATCH v6 3/7] crash_dump: store dm crypt keys in kdump reserved memory

Coiby Xu
2024-10-29T05:52:50Z

When the kdump kernel image and initrd are loaded, the dm crypts keys
will be read from keyring and then stored in kdump reserved memory.

Assume a key won't exceed 256 bytes thus MAX_KEY_SIZE=256 according to
"cryptsetup benchmark".

Signed-off-by: Coiby Xu <coxu@redhat.com>
---
include/linux/crash_core.h | 6 +-
include/linux/kexec.h | 4 ++
kernel/crash_dump_dm_crypt.c | 129 +++++++++++++++++++++++++++++++++++
3 files changed, 138 insertions(+), 1 deletion(-)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 44305336314e..2e6782239034 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -34,7 +34,11 @@ static inline void arch_kexec_protect_crashkres(void) { }
static inline void arch_kexec_unprotect_crashkres(void) { }
#endif

-
+#ifdef CONFIG_CRASH_DM_CRYPT
+int crash_load_dm_crypt_keys(struct kimage *image);
+#else
+static inline int crash_load_dm_crypt_keys(struct kimage *image) {return 0; }
+#endif

#ifndef arch_crash_handle_hotplug_event
static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { }
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 0dc66ca2506a..5bda0978bab3 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -396,6 +396,10 @@ struct kimage {
void *elf_headers;
unsigned long elf_headers_sz;
unsigned long elf_load_addr;
+
+ /* dm crypt keys buffer */
+ unsigned long dm_crypt_keys_addr;
+ unsigned long dm_crypt_keys_sz;
};

/* kexec interface functions */
diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
index 62a3c47d8b3b..ec2ec2967242 100644
--- a/kernel/crash_dump_dm_crypt.c
+++ b/kernel/crash_dump_dm_crypt.c
@@ -1,14 +1,62 @@
// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/key.h>
+#include <linux/keyctl.h>
#include <keys/user-type.h>
#include <linux/crash_dump.h>
#include <linux/configfs.h>
#include <linux/module.h>

#define KEY_NUM_MAX 128 /* maximum dm crypt keys */
+#define KEY_SIZE_MAX 256 /* maximum dm crypt key size */
#define KEY_DESC_MAX_LEN 128 /* maximum dm crypt key description size */

static unsigned int key_count;

+struct dm_crypt_key {
+ unsigned int key_size;
+ char key_desc[KEY_DESC_MAX_LEN];
+ u8 data[KEY_SIZE_MAX];
+};
+
+static struct keys_header {
+ unsigned int total_keys;
+ struct dm_crypt_key keys[] __counted_by(total_keys);
+} *keys_header;
+
+static size_t get_keys_header_size(size_t total_keys)
+{
+ return struct_size(keys_header, keys, total_keys);
+}
+
+static int read_key_from_user_keying(struct dm_crypt_key *dm_key)
+{
+ const struct user_key_payload *ukp;
+ struct key *key;
+
+ kexec_dprintk("Requesting key %s", dm_key->key_desc);
+ key = request_key(&key_type_logon, dm_key->key_desc, NULL);
+
+ if (IS_ERR(key)) {
+ pr_warn("No such key %s\n", dm_key->key_desc);
+ return PTR_ERR(key);
+ }
+
+ ukp = user_key_payload_locked(key);
+ if (!ukp)
+ return -EKEYREVOKED;
+
+ if (ukp->datalen > KEY_SIZE_MAX) {
+ pr_err("Key size %u exceeds maximum (%u)\n", ukp->datalen, KEY_SIZE_MAX);
+ return -EINVAL;
+ }
+
+ memcpy(dm_key->data, ukp->data, ukp->datalen);
+ dm_key->key_size = ukp->datalen;
+ kexec_dprintk("Get dm crypt key (size=%u) %s: %8ph\n", dm_key->key_size,
+ dm_key->key_desc, dm_key->data);
+ return 0;
+}
+
struct config_key {
struct config_item item;
const char *description;
@@ -130,6 +178,87 @@ static struct configfs_subsystem config_keys_subsys = {
},
};

+static int build_keys_header(void)
+{
+ struct config_item *item = NULL;
+ struct config_key *key;
+ int i, r;
+
+ if (keys_header != NULL)
+ kvfree(keys_header);
+
+ keys_header = kzalloc(get_keys_header_size(key_count), GFP_KERNEL);
+ if (!keys_header)
+ return -ENOMEM;
+
+ keys_header->total_keys = key_count;
+
+ i = 0;
+ list_for_each_entry(item, &config_keys_subsys.su_group.cg_children,
+ ci_entry) {
+ if (item->ci_type != &config_key_type)
+ continue;
+
+ key = to_config_key(item);
+
+ strscpy(keys_header->keys[i].key_desc, key->description,
+ KEY_DESC_MAX_LEN);
+ r = read_key_from_user_keying(&keys_header->keys[i]);
+ if (r != 0) {
+ kexec_dprintk("Failed to read key %s\n",
+ keys_header->keys[i].key_desc);
+ return r;
+ }
+ i++;
+ kexec_dprintk("Found key: %s\n", item->ci_name);
+ }
+
+ return 0;
+}
+
+int crash_load_dm_crypt_keys(struct kimage *image)
+{
+ struct kexec_buf kbuf = {
+ .image = image,
+ .buf_min = 0,
+ .buf_max = ULONG_MAX,
+ .top_down = false,
+ .random = true,
+ };
+ int r;
+
+
+ if (key_count <= 0) {
+ kexec_dprintk("No dm-crypt keys\n");
+ return -EINVAL;
+ }
+
+ image->dm_crypt_keys_addr = 0;
+ r = build_keys_header();
+ if (r)
+ return r;
+
+ kbuf.buffer = keys_header;
+ kbuf.bufsz = get_keys_header_size(key_count);
+
+ kbuf.memsz = kbuf.bufsz;
+ kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
+ kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+ r = kexec_add_buffer(&kbuf);
+ if (r) {
+ kvfree((void *)kbuf.buffer);
+ return r;
+ }
+ image->dm_crypt_keys_addr = kbuf.mem;
+ image->dm_crypt_keys_sz = kbuf.bufsz;
+ kexec_dprintk(
+ "Loaded dm crypt keys to kexec_buffer bufsz=0x%lx memsz=0x%lx\n",
+ kbuf.bufsz, kbuf.bufsz);
+
+ return r;
+}
+
+
static int __init configfs_dmcrypt_keys_init(void)
{
int ret;
--
2.47.0