Re: [PATCH v4 2/7] crash_dump: make dm crypt keys persist for the kdump kernel

Baoquan He
2024-06-05T08:22:25Z

On 05/23/24 at 01:04pm, Coiby Xu wrote:
.....
> 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 <keys/user-type.h>
> +#include <linux/crash_dump.h>
> +
> +#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;

These two global variables seems not so necessary. Please see comment at
below.

> +
> +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;
~~~~~~~~
This is the max number a system have from init();
You can add one field member to record how many key slots have been
used.
> + struct dm_crypt_key keys[] __counted_by(key_count);
> +} *keys_header;

Maybe we can rearrange the keys_header like below, the name may not be
very appropriate though.

static struct keys_header {
unsigned int max_key_slots;
unsigned int used_key_slots;
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);
> +}

I personally don't think get_keys_header_size is so necessary. If we
have to keep it, may be we can remove the global variable
keys_header_size, we can call get_keys_header_size() and use local
variable to record the value instead.