From patchwork Fri Sep 24 19:24:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Goyal X-Patchwork-Id: 12516723 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6651DC4332F for ; Fri, 24 Sep 2021 19:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 520FE610CB for ; Fri, 24 Sep 2021 19:25:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346733AbhIXT0u (ORCPT ); Fri, 24 Sep 2021 15:26:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:58542 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346883AbhIXT0r (ORCPT ); Fri, 24 Sep 2021 15:26:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632511513; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=A2r3DRrCNp/SeGau3p3nKIxtm4pHiFpCzkTcRUDfHXg=; b=hjeF9ca7AEf653UT9dEiO2Dtuphq8g1l8YT7mMlA1dMujBJkKiEwfTmSwGt8OhG1ms9foO IKlHGfNqXEHXlLDp6fEidKEe3Cj1DeyyeECGapCtF1QTfSkY+Mm2L9Od30uSjkrMjxPwKf zO/uj6zCTHKIa0sn3hTLeqkOIC5jS70= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-566-R06nNPpOPcGEBppatRdJIA-1; Fri, 24 Sep 2021 15:25:10 -0400 X-MC-Unique: R06nNPpOPcGEBppatRdJIA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3439C1006AA5; Fri, 24 Sep 2021 19:25:09 +0000 (UTC) Received: from horse.redhat.com (unknown [10.22.32.185]) by smtp.corp.redhat.com (Postfix) with ESMTP id 047D15D9CA; Fri, 24 Sep 2021 19:24:57 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 65542228281; Fri, 24 Sep 2021 15:24:56 -0400 (EDT) From: Vivek Goyal To: linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com, selinux@vger.kernel.org, linux-security-module@vger.kernel.org Cc: chirantan@chromium.org, vgoyal@redhat.com, miklos@szeredi.hu, stephen.smalley.work@gmail.com, dwalsh@redhat.com Subject: [PATCH 2/2] fuse: Send security context of inode on file creation Date: Fri, 24 Sep 2021 15:24:42 -0400 Message-Id: <20210924192442.916927-3-vgoyal@redhat.com> In-Reply-To: <20210924192442.916927-1-vgoyal@redhat.com> References: <20210924192442.916927-1-vgoyal@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When a new inode is created, send its security context to server along with creation request (FUSE_CREAT, FUSE_MKNOD, FUSE_MKDIR and FUSE_SYMLINK). This gives server an opportunity to create new file and set security context (possibly atomically). In all the configurations it might not be possible to set context atomically. Like nfs and ceph, use security_dentry_init_security() to dermine security context of inode and send it with create, mkdir, mknod, and symlink requests. Following is the information sent to server. - struct fuse_secctx. This contains total size of security context which follows this structure. - xattr name string. This string represents name of xattr which should be used while setting security context. As of now it is hardcoded to "security.selinux". - security context. This is the actual security context whose size is specified in fuse_secctx struct. This patch is modified version of patch from Chirantan Ekbote Signed-off-by: Vivek Goyal --- fs/fuse/dir.c | 114 ++++++++++++++++++++++++++++++++++++-- fs/fuse/fuse_i.h | 3 + fs/fuse/inode.c | 4 +- include/uapi/linux/fuse.h | 11 ++++ 4 files changed, 126 insertions(+), 6 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index d9b977c0f38d..439bde1ea329 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -17,6 +17,9 @@ #include #include #include +#include +#include +#include static void fuse_advise_use_readdirplus(struct inode *dir) { @@ -456,6 +459,65 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry, return ERR_PTR(err); } +static int get_security_context(struct dentry *entry, umode_t mode, + void **security_ctx, u32 *security_ctxlen) +{ + struct fuse_secctx *fsecctx; + void *ctx, *full_ctx; + u32 ctxlen, full_ctxlen; + int err = 0; + + err = security_dentry_init_security(entry, mode, &entry->d_name, &ctx, + &ctxlen); + if (err) { + if (err != -EOPNOTSUPP) + goto out_err; + /* No LSM is supporting this security hook. Ignore error */ + err = 0; + ctxlen = 0; + } + + if (ctxlen > 0) { + /* + * security_dentry_init_security() does not return the name + * of lsm or xattr to which label belongs. As of now only + * selinux implements this. Hence, hardcoding the name to + * security.selinux. + */ + char *name = "security.selinux"; + void *ptr; + + full_ctxlen = sizeof(*fsecctx) + strlen(name) + ctxlen + 1; + full_ctx = kzalloc(full_ctxlen, GFP_KERNEL); + if (!full_ctx) { + err = -ENOMEM; + kfree(ctx); + goto out_err; + } + + ptr = full_ctx; + fsecctx = (struct fuse_secctx*) ptr; + fsecctx->size = ctxlen; + ptr += sizeof(*fsecctx); + strcpy(ptr, name); + ptr += strlen(name) + 1; + memcpy(ptr, ctx, ctxlen); + kfree(ctx); + } else { + full_ctxlen = sizeof(*fsecctx); + full_ctx = kzalloc(full_ctxlen, GFP_KERNEL); + if (!full_ctx) { + err = -ENOMEM; + goto out_err; + } + } + + *security_ctxlen = full_ctxlen; + *security_ctx = full_ctx; +out_err: + return err; +} + /* * Atomic create+open operation * @@ -476,6 +538,8 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, struct fuse_entry_out outentry; struct fuse_inode *fi; struct fuse_file *ff; + void *security_ctx = NULL; + u32 security_ctxlen; /* Userspace expects S_IFREG in create mode */ BUG_ON((mode & S_IFMT) != S_IFREG); @@ -517,6 +581,18 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, args.out_args[0].value = &outentry; args.out_args[1].size = sizeof(outopen); args.out_args[1].value = &outopen; + + if (fm->fc->init_security) { + err = get_security_context(entry, mode, &security_ctx, + &security_ctxlen); + if (err) + goto out_put_forget_req; + + args.in_numargs = 3; + args.in_args[2].size = security_ctxlen; + args.in_args[2].value = security_ctx; + } + err = fuse_simple_request(fm, &args); if (err) goto out_free_ff; @@ -554,6 +630,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, out_free_ff: fuse_file_free(ff); + kfree(security_ctx); out_put_forget_req: kfree(forget); out_err: @@ -613,13 +690,15 @@ static int fuse_atomic_open(struct inode *dir, struct dentry *entry, */ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args, struct inode *dir, struct dentry *entry, - umode_t mode) + umode_t mode, bool init_security) { struct fuse_entry_out outarg; struct inode *inode; struct dentry *d; int err; struct fuse_forget_link *forget; + void *security_ctx = NULL; + u32 security_ctxlen = 0; if (fuse_is_bad(dir)) return -EIO; @@ -633,7 +712,29 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args, args->out_numargs = 1; args->out_args[0].size = sizeof(outarg); args->out_args[0].value = &outarg; + + if (init_security) { + unsigned short idx = args->in_numargs; + + if ((size_t)idx >= ARRAY_SIZE(args->in_args)) { + err = -ENOMEM; + goto out_put_forget_req; + } + + err = get_security_context(entry, mode, &security_ctx, + &security_ctxlen); + if (err) + goto out_put_forget_req; + + if (security_ctxlen > 0) { + args->in_args[idx].size = security_ctxlen; + args->in_args[idx].value = security_ctx; + args->in_numargs++; + } + } + err = fuse_simple_request(fm, args); + kfree(security_ctx); if (err) goto out_put_forget_req; @@ -691,7 +792,7 @@ static int fuse_mknod(struct user_namespace *mnt_userns, struct inode *dir, args.in_args[0].value = &inarg; args.in_args[1].size = entry->d_name.len + 1; args.in_args[1].value = entry->d_name.name; - return create_new_entry(fm, &args, dir, entry, mode); + return create_new_entry(fm, &args, dir, entry, mode, fm->fc->init_security); } static int fuse_create(struct user_namespace *mnt_userns, struct inode *dir, @@ -719,7 +820,8 @@ static int fuse_mkdir(struct user_namespace *mnt_userns, struct inode *dir, args.in_args[0].value = &inarg; args.in_args[1].size = entry->d_name.len + 1; args.in_args[1].value = entry->d_name.name; - return create_new_entry(fm, &args, dir, entry, S_IFDIR); + return create_new_entry(fm, &args, dir, entry, S_IFDIR, + fm->fc->init_security); } static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir, @@ -735,7 +837,8 @@ static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir, args.in_args[0].value = entry->d_name.name; args.in_args[1].size = len; args.in_args[1].value = link; - return create_new_entry(fm, &args, dir, entry, S_IFLNK); + return create_new_entry(fm, &args, dir, entry, S_IFLNK, + fm->fc->init_security); } void fuse_update_ctime(struct inode *inode) @@ -915,7 +1018,8 @@ static int fuse_link(struct dentry *entry, struct inode *newdir, args.in_args[0].value = &inarg; args.in_args[1].size = newent->d_name.len + 1; args.in_args[1].value = newent->d_name.name; - err = create_new_entry(fm, &args, newdir, newent, inode->i_mode); + err = create_new_entry(fm, &args, newdir, newent, inode->i_mode, + false); /* Contrary to "normal" filesystems it can happen that link makes two "logical" inodes point to the same "physical" inode. We invalidate the attributes of the old one, so it diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 319596df5dc6..885f34f9967f 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -765,6 +765,9 @@ struct fuse_conn { /* Propagate syncfs() to server */ unsigned int sync_fs:1; + /* Initialize security xattrs when creating a new inode */ + unsigned int init_security:1; + /** The number of requests waiting for completion */ atomic_t num_waiting; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 36cd03114b6d..343bc9cfbd92 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1152,6 +1152,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, } if (arg->flags & FUSE_SETXATTR_EXT) fc->setxattr_ext = 1; + if (arg->flags & FUSE_SECURITY_CTX) + fc->init_security = 1; } else { ra_pages = fc->max_read / PAGE_SIZE; fc->no_lock = 1; @@ -1195,7 +1197,7 @@ void fuse_send_init(struct fuse_mount *fm) FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL | FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS | FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA | - FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT; + FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_SECURITY_CTX; #ifdef CONFIG_FUSE_DAX if (fm->fc->dax) ia->in.flags |= FUSE_MAP_ALIGNMENT; diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 2fe54c80051a..777c773e143e 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -986,4 +986,15 @@ struct fuse_syncfs_in { uint64_t padding; }; +/* + * For each security context, send fuse_secctx with size of security context + * fuse_secctx will be followed by security context name and this in turn + * will be followed by actual context label. + * fuse_secctx, name, context + * */ +struct fuse_secctx { + uint32_t size; + uint32_t padding; +}; + #endif /* _LINUX_FUSE_H */