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homework: correct initial minimal fs size calculations by LUKS2/GPT overhead

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So far we assumed we ignore the LUKS2/GPT header overhead when
determining what the lower bound for images sizes is. Let's correct
this.
This commit is contained in:
Lennart Poettering 2021-11-04 23:49:17 +01:00
parent 716bc20034
commit 31ea1bfec1
1 changed files with 13 additions and 1 deletions
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14
src/home/homework-luks.c
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@ -63,6 +63,10 @@
_x > UINT64_MAX - 4095U ? UINT64_MAX : (_x + 4095U) & ~UINT64_C(4095); \
})
/* How much larger will the image on disk be than the fs inside it, i.e. the space we pay for the GPT and
* LUKS2 envelope. (As measured on cryptsetup 2.4.1) */
#define GPT_LUKS2_OVERHEAD UINT64_C(18874368)
static int resize_image_loop(UserRecord *h, HomeSetup *setup, uint64_t old_image_size, uint64_t new_image_size, uint64_t *ret_image_size);
int run_mark_dirty(int fd, bool b) {
@ -1782,6 +1786,8 @@ static int make_partition_table(
assert(first_lba <= UINT64_MAX/512);
start = DISK_SIZE_ROUND_UP(first_lba * 512); /* Round up to multiple of 4K */
log_debug("Starting partition at offset %" PRIu64, start);
if (start == UINT64_MAX)
return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "Overflow while rounding up start LBA.");
@ -1950,6 +1956,10 @@ static int calculate_initial_image_size(UserRecord *h, int image_fd, const char
}
lower_boundary = minimal_size_by_fs_name(fstype);
if (lower_boundary != UINT64_MAX) {
assert(GPT_LUKS2_OVERHEAD < UINT64_MAX - lower_boundary);
lower_boundary += GPT_LUKS2_OVERHEAD;
}
if (lower_boundary == UINT64_MAX || lower_boundary < USER_DISK_SIZE_MIN)
lower_boundary = USER_DISK_SIZE_MIN;
@ -2123,7 +2133,7 @@ int home_create_luks(
else
host_size = DISK_SIZE_ROUND_DOWN(h->disk_size);
if (!supported_fs_size(fstype, host_size))
if (!supported_fs_size(fstype, LESS_BY(host_size, GPT_LUKS2_OVERHEAD)))
return log_error_errno(SYNTHETIC_ERRNO(ERANGE),
"Selected file system size too small for %s.", fstype);
@ -2350,6 +2360,8 @@ int home_create_luks(
print_size_summary(host_size, encrypted_size, &sfs);
log_debug("GPT + LUKS2 overhead is %" PRIu64 " (expected %" PRIu64 ")", host_size - encrypted_size, GPT_LUKS2_OVERHEAD);
*ret_home = TAKE_PTR(new_home);
return 0;
}