This patchset adds support for using fs-verity to validate lowerdata files by specifying an overlay.verity xattr on the metacopy files. This is primarily motivated by the Composefs usecase, where there will be a read-only EROFS layer that contains redirect into a base data layer which has fs-verity enabled on all files. However, it is also useful in general if you want to ensure that the lowerdata files matches the expected content over time. I have also added some tests for this feature to xfstests[1]. This series depends on the commit fsverity: rework fsverity_get_digest() again Which is in the "for-next" branch of https://git.kernel.org/pub/scm/fs/fsverity/linux.git/ This series, plus the above commit are also in git here: https://github.com/alexlarsson/linux/tree/overlay-verity I would love to see this go into 6.5. So Eric, could you maybe Ack the implementation patches separately from the documentation patches? Then maybe we can get this in early, and I promise to try to get the documentation up to standard during the 6.5 cycle as needed. Changes since v3: * Instead of using a overlay.digest xattr we extend the current overlay.metacopy xattr with version, flags and digest. This makes it flexible for later changes and allows us to use the existing xattr lookup to know ahead of time whether a file needs to have verity validated. I've done some performance checks on this new layout, and the results are essentially the same as before. * This is rebased on top of the latest overlayfs-next, which includes the changes to the new mount API, so that part has been redone. * The documentation changes have been rewritten to try to be more clear about the behaviour of i/o verification when verity is used. Changes since v2: * Rebased on top of overlayfs-next * We now alway do verity verification the first time the file content is used, rather than doing it at lookup time for the non-lazy lookup case. Changes since v1: * Rebased on v2 lazy lowerdata series * Dropped the "validate" mount option variant. We now only support "off", "on" and "require", where "off" is the default. * We now store the digest algorithm used in the overlay.verity xattr. * Dropped ability to configure default verity options, as this could cause problems moving layers between machines. * We now properly resolve dependent mount options by automatically enabling metacopy and redirect_dir if verity is on, or failing if the specified options conflict. * Streamlined and fixed the handling of creds in ovl_ensure_verity_loaded(). * Renamed new helpers from ovl_entry_path_ to ovl_e_path_ [1] https://github.com/alexlarsson/xfstests/commits/verity-tests Alexander Larsson (3): ovl: Add framework for verity support ovl: Validate verity xattr when resolving lowerdata ovl: Handle verity during copy-up Documentation/filesystems/fsverity.rst | 2 + Documentation/filesystems/overlayfs.rst | 48 ++++++++ fs/overlayfs/copy_up.c | 47 ++++++- fs/overlayfs/file.c | 8 +- fs/overlayfs/namei.c | 97 +++++++++++++-- fs/overlayfs/overlayfs.h | 53 ++++++-- fs/overlayfs/ovl_entry.h | 1 + fs/overlayfs/super.c | 69 +++++++++-- fs/overlayfs/util.c | 156 +++++++++++++++++++++++- 9 files changed, 448 insertions(+), 33 deletions(-) -- 2.40.1
