[reactos] 01/01: [CMLIB] Clean volatile registry entries in the same manner as Windows (#1883)

[maharmstone]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=e6a9aafe58f8938de7884…

commit e6a9aafe58f8938de7884fd06fb867144fe568ed
Author:     maharmstone <mark(a)harmstone.com>
AuthorDate: Tue Aug 27 01:39:27 2019 +0100
Commit:     Hermès BÉLUSCA - MAÏTO <hermes.belusca-maito(a)reactos.org>
CommitDate: Tue Aug 27 02:39:27 2019 +0200

    [CMLIB] Clean volatile registry entries in the same manner as Windows (#1883)
    
    This fixes the crashes in HvpGetCellMapped on Windows Server 2003 when booting from
Freeloader, as mentioned in maharmstone/btrfs#16.
    
    When the bootloader loads the system hive, it cleans the data pertaining to any
volatile keys. The Windows bootloader does this by setting SubKeyCounts[Volatile] to 0.
After boot, the kernel marks any cell where this is 0 but SubKeyLists[Volatile] isn't
HCELL_NIL as dirty, meaning that the sanitized version will then get flushed to the disk.
    
    Because Freeloader sets SubKeyLists[Volatile] to HCELL_NIL straightaway, Windows
thinks the cell is clean, and can unload it without flushing. If it then reads it from the
disk, it will crash in HvpGetCellMapped due to the stale volatile pointers.
    
    If you break on nt!CmpInitializeSystemHive on Windows and "gu" to the let
the function run, you'll see that DirtyVector of the HHIVE has only the first 8 bits
set. If you run it using the official bootloader, it'll have a lot more than that.
---
 sdk/lib/cmlib/cminit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/lib/cmlib/cminit.c b/sdk/lib/cmlib/cminit.c
index b1b060d8c41..699376e75d9 100644
--- a/sdk/lib/cmlib/cminit.c
+++ b/sdk/lib/cmlib/cminit.c
@@ -120,8 +120,8 @@ CmpPrepareKey(
 
     ASSERT(KeyCell->Signature == CM_KEY_NODE_SIGNATURE);
 
-    KeyCell->SubKeyLists[Volatile] = HCELL_NIL;
     KeyCell->SubKeyCounts[Volatile] = 0;
+    // KeyCell->SubKeyLists[Volatile] = HCELL_NIL; // FIXME! Done only on Windows <
XP.
 
     /* Enumerate and add subkeys */
     if (KeyCell->SubKeyCounts[Stable] > 0)