[PATCH v3 3/7] crash_dump: store dm keys in kdump reserved memory

[Coiby Xu]

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.

Signed-off-by: Coiby Xu <coxu@xxxxxxxxxx>
---
 include/linux/crash_core.h   |  3 ++
 include/linux/crash_dump.h   |  2 +
 include/linux/kexec.h        |  4 ++
 kernel/crash_dump_dm_crypt.c | 87 ++++++++++++++++++++++++++++++++++++
 4 files changed, 96 insertions(+)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 98825b7e0ea6..1f3d5a4fa6c1 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -37,6 +37,9 @@ static inline void arch_kexec_unprotect_crashkres(void) { }
 #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);
+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
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index acc55626afdc..dfd8e4fe6129 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -15,6 +15,8 @@
 extern unsigned long long elfcorehdr_addr;
 extern unsigned long long elfcorehdr_size;
 
+extern unsigned long long dm_crypt_keys_addr;
+
 #ifdef CONFIG_CRASH_DUMP
 extern int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size);
 extern void elfcorehdr_free(unsigned long long addr);
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index fc1e20d565d5..b6cedce66828 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -368,6 +368,10 @@ 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 847499cdcd42..b9997fb53351 100644
--- a/kernel/crash_dump_dm_crypt.c
+++ b/kernel/crash_dump_dm_crypt.c
@@ -1,4 +1,6 @@
 // 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>
 
@@ -111,3 +113,88 @@ 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);
+
+static int read_key_from_user_keying(struct dm_crypt_key *dm_key)
+{
+	const struct user_key_payload *ukp;
+	struct key *key;
+
+	pr_debug("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;
+
+	memcpy(dm_key->data, ukp->data, ukp->datalen);
+	dm_key->key_size = ukp->datalen;
+	pr_debug("Get dm crypt key (size=%u) %s: %8ph\n", dm_key->key_size,
+		 dm_key->key_desc, dm_key->data);
+	return 0;
+}
+
+static int build_keys_header(void)
+{
+	int i, r;
+
+	for (i = 0; i < key_count; i++) {
+		r = read_key_from_user_keying(&keys_header->keys[i]);
+		if (r != 0) {
+			pr_err("Failed to read key %s\n", keys_header->keys[i].key_desc);
+			return r;
+		}
+	}
+
+	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 (state == FRESH)
+		return 0;
+
+	if (key_count != keys_header->key_count) {
+		pr_err("Only record %u keys (%u in total)\n", key_count,
+		       keys_header->key_count);
+		return -EINVAL;
+	}
+
+	image->dm_crypt_keys_addr = 0;
+	r = build_keys_header();
+	if (r)
+		return r;
+
+	kbuf.buffer = keys_header;
+	kbuf.bufsz = keys_header_size;
+
+	kbuf.memsz = kbuf.bufsz;
+	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	r = kexec_add_buffer(&kbuf);
+	if (r) {
+		vfree((void *)kbuf.buffer);
+		return r;
+	}
+	state = LOADED;
+	image->dm_crypt_keys_addr = kbuf.mem;
+	image->dm_crypt_keys_sz = kbuf.bufsz;
+	pr_debug("Loaded dm crypt keys at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		 image->dm_crypt_keys_addr, kbuf.bufsz, kbuf.bufsz);
+
+	return r;
+}
-- 
2.44.0