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efivars: remove direct access to unaligned structure members

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Most of the accesses *were* aligned. The only one that definetely wasn't was to
drive_path->part_start and drive_path->part_size, because those both expect
8 byte alignment, and are at offsets 4 and 12 in the packed structure.

Because of the way that device_path structure is defined and used, we expect
that device_path.length is always two-byte aligned.

This adds asserts in various places to ensure the proper alignment, and uses
memcpy in other places where the alignment might be off.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2019-02-05 17:35:39 +01:00
parent f7cb1c7900
commit 3c7dddaccf
1 changed files with 47 additions and 43 deletions
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90
src/shared/efivars.c
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@ -61,15 +61,19 @@ struct drive_path {
uint8_t signature_type;
} _packed_;
struct device_path {
uint8_t type;
uint8_t sub_type;
uint16_t length;
union {
uint16_t path[0];
struct drive_path drive;
};
} _packed_;
#define device_path__contents { \
uint8_t type; \
uint8_t sub_type; \
uint16_t length; \
union { \
uint16_t path[0]; \
struct drive_path drive; \
}; \
}
struct device_path device_path__contents;
struct device_path__packed device_path__contents _packed_;
assert_cc(sizeof(struct device_path) == sizeof(struct device_path__packed));
bool is_efi_boot(void) {
if (detect_container() > 0)
@ -377,23 +381,29 @@ static ssize_t utf16_size(const uint16_t *s, size_t buf_len_bytes) {
return -EINVAL; /* The terminator was not found */
}
static void efi_guid_to_id128(const void *guid, sd_id128_t *id128) {
struct uuid {
uint32_t u1;
uint16_t u2;
uint16_t u3;
uint8_t u4[8];
} _packed_;
const struct uuid *uuid = guid;
struct guid {
uint32_t u1;
uint16_t u2;
uint16_t u3;
uint8_t u4[8];
} _packed_;
id128->bytes[0] = (uuid->u1 >> 24) & 0xff;
id128->bytes[1] = (uuid->u1 >> 16) & 0xff;
id128->bytes[2] = (uuid->u1 >> 8) & 0xff;
id128->bytes[3] = (uuid->u1) & 0xff;
id128->bytes[4] = (uuid->u2 >> 8) & 0xff;
id128->bytes[5] = (uuid->u2) & 0xff;
id128->bytes[6] = (uuid->u3 >> 8) & 0xff;
id128->bytes[7] = (uuid->u3) & 0xff;
static void efi_guid_to_id128(const void *guid, sd_id128_t *id128) {
uint32_t u1;
uint16_t u2, u3;
const struct guid *uuid = guid;
memcpy(&u1, &uuid->u1, sizeof(uint32_t));
id128->bytes[0] = (u1 >> 24) & 0xff;
id128->bytes[1] = (u1 >> 16) & 0xff;
id128->bytes[2] = (u1 >> 8) & 0xff;
id128->bytes[3] = u1 & 0xff;
memcpy(&u2, &uuid->u2, sizeof(uint16_t));
id128->bytes[4] = (u2 >> 8) & 0xff;
id128->bytes[5] = u2 & 0xff;
memcpy(&u3, &uuid->u3, sizeof(uint16_t));
id128->bytes[6] = (u3 >> 8) & 0xff;
id128->bytes[7] = u3 & 0xff;
memcpy(&id128->bytes[8], uuid->u4, sizeof(uuid->u4));
}
@ -508,20 +518,14 @@ static void to_utf16(uint16_t *dest, const char *src) {
dest[i] = '\0';
}
struct guid {
uint32_t u1;
uint16_t u2;
uint16_t u3;
uint8_t u4[8];
} _packed_;
static void id128_to_efi_guid(sd_id128_t id, void *guid) {
struct guid *uuid = guid;
uuid->u1 = id.bytes[0] << 24 | id.bytes[1] << 16 | id.bytes[2] << 8 | id.bytes[3];
uuid->u2 = id.bytes[4] << 8 | id.bytes[5];
uuid->u3 = id.bytes[6] << 8 | id.bytes[7];
memcpy(uuid->u4, id.bytes+8, sizeof(uuid->u4));
struct guid uuid = {
.u1 = id.bytes[0] << 24 | id.bytes[1] << 16 | id.bytes[2] << 8 | id.bytes[3],
.u2 = id.bytes[4] << 8 | id.bytes[5],
.u3 = id.bytes[6] << 8 | id.bytes[7],
};
memcpy(uuid.u4, id.bytes+8, sizeof(uuid.u4));
memcpy(guid, &uuid, sizeof(uuid));
}
static uint16_t *tilt_slashes(uint16_t *s) {
@ -575,12 +579,12 @@ int efi_add_boot_option(
devicep->type = MEDIA_DEVICE_PATH;
devicep->sub_type = MEDIA_HARDDRIVE_DP;
devicep->length = offsetof(struct device_path, drive) + sizeof(struct drive_path);
devicep->drive.part_nr = part;
devicep->drive.part_start = pstart;
devicep->drive.part_size = psize;
devicep->drive.signature_type = SIGNATURE_TYPE_GUID;
devicep->drive.mbr_type = MBR_TYPE_EFI_PARTITION_TABLE_HEADER;
memcpy(&devicep->drive.part_nr, &part, sizeof(uint32_t));
memcpy(&devicep->drive.part_start, &pstart, sizeof(uint64_t));
memcpy(&devicep->drive.part_size, &psize, sizeof(uint64_t));
id128_to_efi_guid(part_uuid, devicep->drive.signature);
devicep->drive.mbr_type = MBR_TYPE_EFI_PARTITION_TABLE_HEADER;
devicep->drive.signature_type = SIGNATURE_TYPE_GUID;
size += devicep->length;
/* path to loader */