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authorAlexander Larsson <alexl@redhat.com>2023-06-21 11:32:31 +0300
committerAmir Goldstein <amir73il@gmail.com>2023-08-12 19:02:38 +0300
commitbf07089081a0ea18da4a103b9d813ffae3c2f6d8 (patch)
tree4402aa478356f3d607045ddf43b04bd7c910b82b /fs/overlayfs/overlayfs.h
parentae8cba4033bc16e8a07792428a48a50710cc0f3c (diff)
downloadlinux-bf07089081a0ea18da4a103b9d813ffae3c2f6d8.tar.xz
ovl: Add versioned header for overlay.metacopy xattr
Historically overlay.metacopy was a zero-size xattr, and it's existence marked a metacopy file. This change adds a versioned header with a flag field, a length and a digest. The initial use-case of this will be for validating a fs-verity digest, but the flags field could also be used later for other new features. ovl_check_metacopy_xattr() now returns the size of the xattr, emulating a size of OVL_METACOPY_MIN_SIZE for empty xattrs to distinguish it from the no-xattr case. Signed-off-by: Alexander Larsson <alexl@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Diffstat (limited to 'fs/overlayfs/overlayfs.h')
-rw-r--r--fs/overlayfs/overlayfs.h24
1 files changed, 23 insertions, 1 deletions
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 34cc72f8fb6a..2e659b355f61 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -7,6 +7,7 @@
#include <linux/kernel.h>
#include <linux/uuid.h>
#include <linux/fs.h>
+#include <linux/fsverity.h>
#include <linux/namei.h>
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>
@@ -132,6 +133,26 @@ struct ovl_fh {
#define OVL_FH_FID_OFFSET (OVL_FH_WIRE_OFFSET + \
offsetof(struct ovl_fb, fid))
+/* On-disk format for "metacopy" xattr (if non-zero size) */
+struct ovl_metacopy {
+ u8 version; /* 0 */
+ u8 len; /* size of this header + used digest bytes */
+ u8 flags;
+ u8 digest_algo; /* FS_VERITY_HASH_ALG_* constant, 0 for no digest */
+ u8 digest[FS_VERITY_MAX_DIGEST_SIZE]; /* Only the used part on disk */
+} __packed;
+
+#define OVL_METACOPY_MAX_SIZE (sizeof(struct ovl_metacopy))
+#define OVL_METACOPY_MIN_SIZE (OVL_METACOPY_MAX_SIZE - FS_VERITY_MAX_DIGEST_SIZE)
+#define OVL_METACOPY_INIT { 0, OVL_METACOPY_MIN_SIZE }
+
+static inline int ovl_metadata_digest_size(const struct ovl_metacopy *metacopy)
+{
+ if (metacopy->len < OVL_METACOPY_MIN_SIZE)
+ return 0;
+ return (int)metacopy->len - OVL_METACOPY_MIN_SIZE;
+}
+
extern const char *const ovl_xattr_table[][2];
static inline const char *ovl_xattr(struct ovl_fs *ofs, enum ovl_xattr ox)
{
@@ -458,7 +479,8 @@ bool ovl_need_index(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry);
void ovl_nlink_end(struct dentry *dentry);
int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
-int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path);
+int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path,
+ struct ovl_metacopy *data);
bool ovl_is_metacopy_dentry(struct dentry *dentry);
char *ovl_get_redirect_xattr(struct ovl_fs *ofs, const struct path *path, int padding);
int ovl_sync_status(struct ovl_fs *ofs);