[PATCH 1/4] xfs: hide private inodes from bulkstat and handle functions

Darrick J. Wong
2023-12-31T20:31:02Z

We're about to start adding functionality that uses internal inodes that
are private to XFS. What this means is that userspace should never be
able to access any information about these files, and should not be able
to open these files by handle. Callers are not allowed to link these
files into the directory tree, which should suffice to make these
private inodes actually private.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/xfs_export.c | 2 +-
fs/xfs/xfs_itable.c | 8 ++++++++
2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
index 7cd09c3a82cb5..4b03221351c0f 100644
--- a/fs/xfs/xfs_export.c
+++ b/fs/xfs/xfs_export.c
@@ -160,7 +160,7 @@ xfs_nfs_get_inode(
}
}

- if (VFS_I(ip)->i_generation != generation) {
+ if (VFS_I(ip)->i_generation != generation || IS_PRIVATE(VFS_I(ip))) {
xfs_irele(ip);
return ERR_PTR(-ESTALE);
}
diff --git a/fs/xfs/xfs_itable.c b/fs/xfs/xfs_itable.c
index 14462614fcc8d..4610660f267e6 100644
--- a/fs/xfs/xfs_itable.c
+++ b/fs/xfs/xfs_itable.c
@@ -97,6 +97,14 @@ xfs_bulkstat_one_int(
vfsuid = i_uid_into_vfsuid(idmap, inode);
vfsgid = i_gid_into_vfsgid(idmap, inode);

+ /* If this is a private inode, don't leak its details to userspace. */
+ if (IS_PRIVATE(inode)) {
+ xfs_iunlock(ip, XFS_ILOCK_SHARED);
+ xfs_irele(ip);
+ error = -EINVAL;
+ goto out_advance;
+ }
+
/* xfs_iget returns the following without needing
* further change.
*/