[CMLIB] Clean volatile registry entries in the same manner as Windows #1883
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@maharmstone : You said that while investigating on Windows you see that the SubKeyLists[Volatile] value is not HCELL_NIL. Could you please tell me which one you actually read instead? |
|
Whatever happened to be its value when it was flushed to disk on the last boot. 80016178 in this particular case, I believe. |
HBelusca
approved these changes
Aug 27, 2019
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.
Bear in mind that I haven't tested this either on ReactOS, or any other version of Windows - but it's definitely the case for WS2003. You probably want to do your own testing before accepting this patch.