Merge tag 'ovl-update-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs

Pull overlayfs updates from Amir Goldstein:

 - add verification feature needed by composefs (Alexander Larsson)

 - improve integration of overlayfs and fanotify (Amir Goldstein)

 - fortify some overlayfs code (Andrea Righi)

* tag 'ovl-update-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs:
  ovl: validate superblock in OVL_FS()
  ovl: make consistent use of OVL_FS()
  ovl: Kconfig: introduce CONFIG_OVERLAY_FS_DEBUG
  ovl: auto generate uuid for new overlay filesystems
  ovl: store persistent uuid/fsid with uuid=on
  ovl: add support for unique fsid per instance
  ovl: support encoding non-decodable file handles
  ovl: Handle verity during copy-up
  ovl: Validate verity xattr when resolving lowerdata
  ovl: Add versioned header for overlay.metacopy xattr
  ovl: Add framework for verity support

1 files changed, 221 insertions, 12 deletions

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index c210b5d496a8..89e0d60d35b6 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -10,6 +10,7 @@
 #include <linux/cred.h>
 #include <linux/xattr.h>
 #include <linux/exportfs.h>
+#include <linux/file.h>
 #include <linux/fileattr.h>
 #include <linux/uuid.h>
 #include <linux/namei.h>
@@ -18,25 +19,25 @@
 
 int ovl_want_write(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	return mnt_want_write(ovl_upper_mnt(ofs));
 }
 
 void ovl_drop_write(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	mnt_drop_write(ovl_upper_mnt(ofs));
 }
 
 struct dentry *ovl_workdir(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	return ofs->workdir;
 }
 
 const struct cred *ovl_override_creds(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return override_creds(ofs->creator_cred);
 }
@@ -62,7 +63,7 @@ int ovl_can_decode_fh(struct super_block *sb)
 
 struct dentry *ovl_indexdir(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->indexdir;
 }
@@ -70,7 +71,7 @@ struct dentry *ovl_indexdir(struct super_block *sb)
 /* Index all files on copy up. For now only enabled for NFS export */
 bool ovl_index_all(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->config.nfs_export && ofs->config.index;
 }
@@ -78,7 +79,7 @@ bool ovl_index_all(struct super_block *sb)
 /* Verify lower origin on lookup. For now only enabled for NFS export */
 bool ovl_verify_lower(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->config.nfs_export && ofs->config.index;
 }
@@ -203,7 +204,7 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry)
 
 void ovl_path_upper(struct dentry *dentry, struct path *path)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 
 	path->mnt = ovl_upper_mnt(ofs);
 	path->dentry = ovl_dentry_upper(dentry);
@@ -675,6 +676,65 @@ bool ovl_path_check_origin_xattr(struct ovl_fs *ofs, const struct path *path)
 	return false;
 }
 
+/*
+ * Load persistent uuid from xattr into s_uuid if found, or store a new
+ * random generated value in s_uuid and in xattr.
+ */
+bool ovl_init_uuid_xattr(struct super_block *sb, struct ovl_fs *ofs,
+			 const struct path *upperpath)
+{
+	bool set = false;
+	int res;
+
+	/* Try to load existing persistent uuid */
+	res = ovl_path_getxattr(ofs, upperpath, OVL_XATTR_UUID, sb->s_uuid.b,
+				UUID_SIZE);
+	if (res == UUID_SIZE)
+		return true;
+
+	if (res != -ENODATA)
+		goto fail;
+
+	/*
+	 * With uuid=auto, if uuid xattr is found, it will be used.
+	 * If uuid xattrs is not found, generate a persistent uuid only on mount
+	 * of new overlays where upper root dir is not yet marked as impure.
+	 * An upper dir is marked as impure on copy up or lookup of its subdirs.
+	 */
+	if (ofs->config.uuid == OVL_UUID_AUTO) {
+		res = ovl_path_getxattr(ofs, upperpath, OVL_XATTR_IMPURE, NULL,
+					0);
+		if (res > 0) {
+			/* Any mount of old overlay - downgrade to uuid=null */
+			ofs->config.uuid = OVL_UUID_NULL;
+			return true;
+		} else if (res == -ENODATA) {
+			/* First mount of new overlay - upgrade to uuid=on */
+			ofs->config.uuid = OVL_UUID_ON;
+		} else if (res < 0) {
+			goto fail;
+		}
+
+	}
+
+	/* Generate overlay instance uuid */
+	uuid_gen(&sb->s_uuid);
+
+	/* Try to store persistent uuid */
+	set = true;
+	res = ovl_setxattr(ofs, upperpath->dentry, OVL_XATTR_UUID, sb->s_uuid.b,
+			   UUID_SIZE);
+	if (res == 0)
+		return true;
+
+fail:
+	memset(sb->s_uuid.b, 0, UUID_SIZE);
+	ofs->config.uuid = OVL_UUID_NULL;
+	pr_warn("failed to %s uuid (%pd2, err=%i); falling back to uuid=null.\n",
+		set ? "set" : "get", upperpath->dentry, res);
+	return false;
+}
+
 bool ovl_path_check_dir_xattr(struct ovl_fs *ofs, const struct path *path,
 			       enum ovl_xattr ox)
 {
@@ -697,6 +757,7 @@ bool ovl_path_check_dir_xattr(struct ovl_fs *ofs, const struct path *path,
 #define OVL_XATTR_IMPURE_POSTFIX	"impure"
 #define OVL_XATTR_NLINK_POSTFIX		"nlink"
 #define OVL_XATTR_UPPER_POSTFIX		"upper"
+#define OVL_XATTR_UUID_POSTFIX		"uuid"
 #define OVL_XATTR_METACOPY_POSTFIX	"metacopy"
 #define OVL_XATTR_PROTATTR_POSTFIX	"protattr"
 
@@ -711,6 +772,7 @@ const char *const ovl_xattr_table[][2] = {
 	OVL_XATTR_TAB_ENTRY(OVL_XATTR_IMPURE),
 	OVL_XATTR_TAB_ENTRY(OVL_XATTR_NLINK),
 	OVL_XATTR_TAB_ENTRY(OVL_XATTR_UPPER),
+	OVL_XATTR_TAB_ENTRY(OVL_XATTR_UUID),
 	OVL_XATTR_TAB_ENTRY(OVL_XATTR_METACOPY),
 	OVL_XATTR_TAB_ENTRY(OVL_XATTR_PROTATTR),
 };
@@ -1054,8 +1116,12 @@ err:
 	return -EIO;
 }
 
-/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
-int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path)
+/*
+ * err < 0, 0 if no metacopy xattr, metacopy data size if xattr found.
+ * an empty xattr returns OVL_METACOPY_MIN_SIZE to distinguish from no xattr value.
+ */
+int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path,
+			     struct ovl_metacopy *data)
 {
 	int res;
 
@@ -1063,7 +1129,8 @@ int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path)
 	if (!S_ISREG(d_inode(path->dentry)->i_mode))
 		return 0;
 
-	res = ovl_path_getxattr(ofs, path, OVL_XATTR_METACOPY, NULL, 0);
+	res = ovl_path_getxattr(ofs, path, OVL_XATTR_METACOPY,
+				data, data ? OVL_METACOPY_MAX_SIZE : 0);
 	if (res < 0) {
 		if (res == -ENODATA || res == -EOPNOTSUPP)
 			return 0;
@@ -1077,12 +1144,48 @@ int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path)
 		goto out;
 	}
 
-	return 1;
+	if (res == 0) {
+		/* Emulate empty data for zero size metacopy xattr */
+		res = OVL_METACOPY_MIN_SIZE;
+		if (data) {
+			memset(data, 0, res);
+			data->len = res;
+		}
+	} else if (res < OVL_METACOPY_MIN_SIZE) {
+		pr_warn_ratelimited("metacopy file '%pd' has too small xattr\n",
+				    path->dentry);
+		return -EIO;
+	} else if (data) {
+		if (data->version != 0) {
+			pr_warn_ratelimited("metacopy file '%pd' has unsupported version\n",
+					    path->dentry);
+			return -EIO;
+		}
+		if (res != data->len) {
+			pr_warn_ratelimited("metacopy file '%pd' has invalid xattr size\n",
+					    path->dentry);
+			return -EIO;
+		}
+	}
+
+	return res;
 out:
 	pr_warn_ratelimited("failed to get metacopy (%i)\n", res);
 	return res;
 }
 
+int ovl_set_metacopy_xattr(struct ovl_fs *ofs, struct dentry *d, struct ovl_metacopy *metacopy)
+{
+	size_t len = metacopy->len;
+
+	/* If no flags or digest fall back to empty metacopy file */
+	if (metacopy->version == 0 && metacopy->flags == 0 && metacopy->digest_algo == 0)
+		len = 0;
+
+	return ovl_check_setxattr(ofs, d, OVL_XATTR_METACOPY,
+				  metacopy, len, -EOPNOTSUPP);
+}
+
 bool ovl_is_metacopy_dentry(struct dentry *dentry)
 {
 	struct ovl_entry *oe = OVL_E(dentry);
@@ -1145,6 +1248,112 @@ err_free:
 	return ERR_PTR(res);
 }
 
+/* Call with mounter creds as it may open the file */
+int ovl_ensure_verity_loaded(struct path *datapath)
+{
+	struct inode *inode = d_inode(datapath->dentry);
+	struct file *filp;
+
+	if (!fsverity_active(inode) && IS_VERITY(inode)) {
+		/*
+		 * If this inode was not yet opened, the verity info hasn't been
+		 * loaded yet, so we need to do that here to force it into memory.
+		 */
+		filp = kernel_file_open(datapath, O_RDONLY, inode, current_cred());
+		if (IS_ERR(filp))
+			return PTR_ERR(filp);
+		fput(filp);
+	}
+
+	return 0;
+}
+
+int ovl_validate_verity(struct ovl_fs *ofs,
+			struct path *metapath,
+			struct path *datapath)
+{
+	struct ovl_metacopy metacopy_data;
+	u8 actual_digest[FS_VERITY_MAX_DIGEST_SIZE];
+	int xattr_digest_size, digest_size;
+	int xattr_size, err;
+	u8 verity_algo;
+
+	if (!ofs->config.verity_mode ||
+	    /* Verity only works on regular files */
+	    !S_ISREG(d_inode(metapath->dentry)->i_mode))
+		return 0;
+
+	xattr_size = ovl_check_metacopy_xattr(ofs, metapath, &metacopy_data);
+	if (xattr_size < 0)
+		return xattr_size;
+
+	if (!xattr_size || !metacopy_data.digest_algo) {
+		if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
+			pr_warn_ratelimited("metacopy file '%pd' has no digest specified\n",
+					    metapath->dentry);
+			return -EIO;
+		}
+		return 0;
+	}
+
+	xattr_digest_size = ovl_metadata_digest_size(&metacopy_data);
+
+	err = ovl_ensure_verity_loaded(datapath);
+	if (err < 0) {
+		pr_warn_ratelimited("lower file '%pd' failed to load fs-verity info\n",
+				    datapath->dentry);
+		return -EIO;
+	}
+
+	digest_size = fsverity_get_digest(d_inode(datapath->dentry), actual_digest,
+					  &verity_algo, NULL);
+	if (digest_size == 0) {
+		pr_warn_ratelimited("lower file '%pd' has no fs-verity digest\n", datapath->dentry);
+		return -EIO;
+	}
+
+	if (xattr_digest_size != digest_size ||
+	    metacopy_data.digest_algo != verity_algo ||
+	    memcmp(metacopy_data.digest, actual_digest, xattr_digest_size) != 0) {
+		pr_warn_ratelimited("lower file '%pd' has the wrong fs-verity digest\n",
+				    datapath->dentry);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+int ovl_get_verity_digest(struct ovl_fs *ofs, struct path *src,
+			  struct ovl_metacopy *metacopy)
+{
+	int err, digest_size;
+
+	if (!ofs->config.verity_mode || !S_ISREG(d_inode(src->dentry)->i_mode))
+		return 0;
+
+	err = ovl_ensure_verity_loaded(src);
+	if (err < 0) {
+		pr_warn_ratelimited("lower file '%pd' failed to load fs-verity info\n",
+				    src->dentry);
+		return -EIO;
+	}
+
+	digest_size = fsverity_get_digest(d_inode(src->dentry),
+					  metacopy->digest, &metacopy->digest_algo, NULL);
+	if (digest_size == 0 ||
+	    WARN_ON_ONCE(digest_size > FS_VERITY_MAX_DIGEST_SIZE)) {
+		if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
+			pr_warn_ratelimited("lower file '%pd' has no fs-verity digest\n",
+					    src->dentry);
+			return -EIO;
+		}
+		return 0;
+	}
+
+	metacopy->len += digest_size;
+	return 0;
+}
+
 /*
  * ovl_sync_status() - Check fs sync status for volatile mounts
  *