Don't fchdir at unmount when mounting read-only #19
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
Prior to this commit, after the fuse_loop function returns (e.g. as a result of "fusermount -u" or equivalent from a separate process), this main function would call fchdir(oldpwd) unconditionally and then, if the archive was modified (in memory), rewrite the archive on disk. This commit changes the "unconditionally" part so that fchdir is only called if we're about to rewrite the archive on disk. Walking backwards, the original working directory (the oldpwd variable) is no longer read if options.readonly is true, as it is not used anywhere else. For a read-only mount, the fchdir would just be unnecessary work. More importantly, when running archivemount (in read-only mode) in a syscall-based sandbox (e.g. minijail), removing the unconditionality of the fchdir call means fewer syscalls in our allow-list.
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Outdated suggestions cannot be applied.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.
Prior to this commit, after the fuse_loop function returns (e.g. as a
result of "fusermount -u" or equivalent from a separate process), this
main function would call fchdir(oldpwd) unconditionally and then, if the
archive was modified (in memory), rewrite the archive on disk.
This commit changes the "unconditionally" part so that fchdir is only
called if we're about to rewrite the archive on disk. Walking backwards,
the original working directory (the oldpwd variable) is no longer read
if options.readonly is true, as it is not used anywhere else.
For a read-only mount, the fchdir would just be unnecessary work. More
importantly, when running archivemount (in read-only mode) in a
syscall-based sandbox (e.g. minijail), removing the unconditionality of
the fchdir call means fewer syscalls in our allow-list.