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boot: reject GPT headers with SizeOfPartitionEntry below the minimum

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Commit 0cf5f816f2 replaced the original lower-bound check

    if (h->SizeOfPartitionEntry < sizeof(EFI_PARTITION_ENTRY))
            return false;

with a multiple-of check

    if ((h->SizeOfPartitionEntry % sizeof(EFI_PARTITION_ENTRY)) != 0)
            return false;

to additionally require the entry size to be a multiple of 128. The
modulo test is however also satisfied by SizeOfPartitionEntry == 0, so a
GPT header advertising a zero entry size now passes verify_gpt().

Restore the lower bound in addition to the multiple-of check, so the
entry size must be at least sizeof(EFI_PARTITION_ENTRY) and a multiple of
it (128 bytes).

Follow-up for 0cf5f816f2

(cherry picked from commit d06d8a232b)
(cherry picked from commit e233936dbc)
This commit is contained in:
Luca Boccassi
2026-06-26 17:15:38 +01:00
parent 51f9f9f6d7
commit 9dfd1cdfc3
1 changed files with 2 additions and 1 deletions
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3
src/boot/part-discovery.c
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@@ -57,7 +57,8 @@ static bool verify_gpt(/* const */ GptHeader *h, EFI_LBA lba_expected) {
if (h->MyLBA != lba_expected)
return false;
if ((h->SizeOfPartitionEntry % sizeof(EFI_PARTITION_ENTRY)) != 0)
if (h->SizeOfPartitionEntry < sizeof(EFI_PARTITION_ENTRY) ||
(h->SizeOfPartitionEntry % sizeof(EFI_PARTITION_ENTRY)) != 0)
return false;
if (h->NumberOfPartitionEntries <= 0 || h->NumberOfPartitionEntries > 1024)