FileManagement: Hide the FEX RootFS fd from /proc/self/fd #4138
+65
−5
Conversation
This file contains 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
Chromium/CEF has code that iterates through all open FDs and bails if any are directories (apparently a sandboxing sanity check). To avoid this check, we need to hide the RootFS FD. This requires hooking all the getdents variants to skip that entry. To keep the runtime cost low, we keep track of the inode of /proc/self/fd/<rootfs fd> (note: not the RootFS inode, the inode of the magic symlink in /proc), and first do a quick check on that. If it matches, then we stat the dirfd we are reading and check against the procfs device, to complete the inode equality check. As an extra benefit, this also fixes code that tries to iterate and close all/extra FDs and ends up closing the RootFS fd.
Sonicadvance1
approved these changes
Oct 26, 2024
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Outdated suggestions cannot be applied.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.
Chromium/CEF has code that iterates through all open FDs and bails if any are directories (apparently a sandboxing sanity check). To avoid this check, we need to hide the RootFS FD. This requires hooking all the getdents variants to skip that entry.
To keep the runtime cost low, we keep track of the inode of /proc/self/fd/ (note: not the RootFS inode, the inode of the magic symlink in /proc), and first do a quick check on that. If it matches, then we stat the dirfd we are reading and check against the procfs device, to complete the inode equality check.
As an extra benefit, this also fixes code that tries to iterate and close all/extra FDs and ends up closing the RootFS fd.