[reactos] 01/01: [NTOS:FSTUB] Pack the MASTER_BOOT_RECORD structure (#6416)

[Adam Słaboń]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=1f28f715ba14d2f3c99e0…

commit 1f28f715ba14d2f3c99e016a1a9e5e710d2b6809
Author:     Adam Słaboń <asaillen(a)protonmail.com>
AuthorDate: Wed Feb 7 23:02:19 2024 +0100
Commit:     GitHub <noreply(a)github.com>
CommitDate: Thu Feb 8 01:02:19 2024 +0300

    [NTOS:FSTUB] Pack the MASTER_BOOT_RECORD structure (#6416)
    
    Otherwise the USHORT members are aligned to 4-byte boundary space
    which overflows the disk sector buffer and ultimately results in crash.
    This can be reproduced by trying to format the USB drive with Rufus.
    
    Also put some additional C_ASSERT checks for extra safety.
---
 ntoskrnl/fstub/fstubex.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/ntoskrnl/fstub/fstubex.c b/ntoskrnl/fstub/fstubex.c
index 1904d32339a..00d4ae30fd4 100644
--- a/ntoskrnl/fstub/fstubex.c
+++ b/ntoskrnl/fstub/fstubex.c
@@ -41,6 +41,7 @@ typedef struct _EFI_PARTITION_HEADER
     ULONG SizeOfPartitionEntry;  // 84
     ULONG PartitionEntryCRC32;   // 88
 } EFI_PARTITION_HEADER, *PEFI_PARTITION_HEADER;
+C_ASSERT(sizeof(EFI_PARTITION_HEADER) == 92);
 #include <poppack.h>
 
 typedef struct _EFI_PARTITION_ENTRY
@@ -52,6 +53,7 @@ typedef struct _EFI_PARTITION_ENTRY
     ULONGLONG Attributes;  // 48
     WCHAR Name[0x24];      // 56
 } EFI_PARTITION_ENTRY, *PEFI_PARTITION_ENTRY;
+C_ASSERT(sizeof(EFI_PARTITION_ENTRY) == 128);
 
 typedef struct _PARTITION_TABLE_ENTRY
 {
@@ -66,7 +68,9 @@ typedef struct _PARTITION_TABLE_ENTRY
     ULONG SectorCountBeforePartition;
     ULONG PartitionSectorCount;
 } PARTITION_TABLE_ENTRY, *PPARTITION_TABLE_ENTRY;
+C_ASSERT(sizeof(PARTITION_TABLE_ENTRY) == 16);
 
+#include <pshpack1.h>
 typedef struct _MASTER_BOOT_RECORD
 {
     UCHAR MasterBootRecordCodeAndData[0x1B8]; // 0
@@ -75,6 +79,8 @@ typedef struct _MASTER_BOOT_RECORD
     PARTITION_TABLE_ENTRY PartitionTable[4];  // 446
     USHORT MasterBootRecordMagic;             // 510
 } MASTER_BOOT_RECORD, *PMASTER_BOOT_RECORD;
+C_ASSERT(sizeof(MASTER_BOOT_RECORD) == 512);
+#include <poppack.h>
 
 /* Partition entry size (bytes) - FIXME: It's hardcoded as Microsoft does, but
according to specs, it shouldn't be */
 #define PARTITION_ENTRY_SIZE 128