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Date: Tue, 21 May 2024 11:42:52 +0800
From: Baoquan He <bhe@...hat.com>
To: Coiby Xu <coxu@...hat.com>
Cc: kexec@...ts.infradead.org, Ondrej Kozina <okozina@...hat.com>,
Milan Broz <gmazyland@...il.com>,
Thomas Staudt <tstaudt@...ibm.com>,
Daniel P . Berrangé <berrange@...hat.com>,
Kairui Song <ryncsn@...il.com>,
. Jan Pazdziora <jpazdziora@...hat.com>,
Pingfan Liu <kernelfans@...il.com>, Dave Young <dyoung@...hat.com>,
linux-kernel@...r.kernel.org, x86@...nel.org,
Dave Hansen <dave.hansen@...el.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Vivek Goyal <vgoyal@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH v3 3/7] crash_dump: store dm keys in kdump reserved memory
On 04/25/24 at 06:04pm, Coiby Xu wrote:
> 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@...hat.com>
> ---
> 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);
Please use kexec_dprintk() instead to print debugging message.
And you don't worry this printing will leak the key position and the
information?
> +
> + return r;
> +}
> --
> 2.44.0
>
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