diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst index ab989807a2cb..af5a69f87da4 100644 --- a/Documentation/filesystems/overlayfs.rst +++ b/Documentation/filesystems/overlayfs.rst @@ -753,9 +753,9 @@ Note: the mount options index=off,nfs_export=on are conflicting for a read-write mount and will result in an error. Note: the mount option uuid=off can be used to replace UUID of the underlying -filesystem in file handles with null, and effectively disable UUID checks. This +filesystem in file handles with null, in order to relax the UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy -is changed. This is only applicable if all lower/upper/work directories are on +is changed. This is only applicable if all lower directories are on the same filesystem, otherwise it will fallback to normal behaviour. @@ -769,7 +769,7 @@ controlled by the "uuid" mount option, which supports these values: UUID of overlayfs is null. fsid is taken from upper most filesystem. - "off": UUID of overlayfs is null. fsid is taken from upper most filesystem. - UUID of underlying layers is ignored. + UUID of underlying layers is ignored and null used instead. - "on": UUID of overlayfs is generated and used to report a unique fsid. UUID is stored in xattr "trusted.overlay.uuid", making overlayfs fsid diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index cda26bdef3b9..afb7019fd43a 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -159,6 +159,18 @@ invalid: goto out; } +bool ovl_uuid_match(struct ovl_fs *ofs, const struct super_block *sb, + const uuid_t *uuid) +{ + /* + * Make sure that the stored uuid matches the uuid of the lower + * layer where file handle will be decoded. + * In case of uuid=off option just make sure that stored uuid is null. + */ + return ovl_origin_uuid(ofs) ? uuid_equal(uuid, &sb->s_uuid) : + uuid_is_null(uuid); +} + struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, struct vfsmount *mnt, bool connected) { @@ -168,14 +180,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, if (!capable(CAP_DAC_READ_SEARCH)) return NULL; - /* - * Make sure that the stored uuid matches the uuid of the lower - * layer where file handle will be decoded. - * In case of uuid=off option just make sure that stored uuid is null. - */ - if (ovl_origin_uuid(ofs) ? - !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid) : - !uuid_is_null(&fh->fb.uuid)) + if (!ovl_uuid_match(ofs, mnt->mnt_sb, &fh->fb.uuid)) return NULL; bytes = (fh->fb.len - offsetof(struct ovl_fb, fid)); diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 315882a360ce..cad2055ebf18 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -710,6 +710,8 @@ static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) return ovl_check_fb_len(&fh->fb, fh_len - OVL_FH_WIRE_OFFSET); } +bool ovl_uuid_match(struct ovl_fs *ofs, const struct super_block *sb, + const uuid_t *uuid); struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, struct vfsmount *mnt, bool connected); int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index ba9146f22a2c..c9f166a1390a 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -940,7 +940,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) * disable lower file handle decoding on all of them. */ if (ofs->fs[i].is_lower && - uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) { + ovl_uuid_match(ofs, ofs->fs[i].sb, uuid)) { ofs->fs[i].bad_uuid = true; return false; } @@ -952,6 +952,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) { struct super_block *sb = path->mnt->mnt_sb; + const uuid_t *uuid = ovl_origin_uuid(ofs) ? &sb->s_uuid : &uuid_null; unsigned int i; dev_t dev; int err; @@ -963,7 +964,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) return i; } - if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { + if (!ovl_lower_uuid_ok(ofs, uuid)) { bad_uuid = true; if (ofs->config.xino == OVL_XINO_AUTO) { ofs->config.xino = OVL_XINO_OFF; @@ -975,9 +976,8 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) warn = true; } if (warn) { - pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n", - uuid_is_null(&sb->s_uuid) ? "null" : - "conflicting", + pr_warn("%s uuid in non-single lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n", + uuid_is_null(uuid) ? "null" : "conflicting", path->dentry, ovl_xino_mode(&ofs->config)); } } @@ -1469,10 +1469,7 @@ static int ovl_fill_super_creds(struct fs_context *fc, struct super_block *sb) if (!ovl_upper_mnt(ofs)) sb->s_flags |= SB_RDONLY; - if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) { - pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n"); - ofs->config.uuid = OVL_UUID_NULL; - } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) { + if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) { /* Use per instance persistent uuid/fsid */ ovl_init_uuid_xattr(sb, ofs, &ctx->upper); }