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Message-ID: <akqkcxxeg35lwxgd2nszgul7zpzkcfjzdx7zw5udsm24vcjbiy@vvtgme6nizjq>
Date: Fri, 24 May 2024 15:38:18 +0800
From: Coiby Xu <coxu@...hat.com>
To: Baoquan He <bhe@...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 Tue, May 21, 2024 at 11:42:52AM +0800, Baoquan He wrote:
>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.
Thanks for pointing me to kexec_dprintk! I'll use kexec_dprintk.
>And you don't worry this printing will leak the key position and the
>information?
Thanks for raising this concern! I'll remove the key position info as it
seems kernel dyndbg can be easily enabled.
--
Best regards,
Coiby
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