From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ECC78C433FF for ; Tue, 30 Jul 2019 17:29:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA4D020693 for ; Tue, 30 Jul 2019 17:29:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="cT4SN6lh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728935AbfG3R3v (ORCPT ); Tue, 30 Jul 2019 13:29:51 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:38013 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730828AbfG3R3u (ORCPT ); Tue, 30 Jul 2019 13:29:50 -0400 Received: by mail-pg1-f196.google.com with SMTP id f5so21595784pgu.5 for ; Tue, 30 Jul 2019 10:29:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=hLTD2Uw33ruzT4aIF9v59VNMUBom9/69Xaztq/CP3Xc=; b=cT4SN6lhozZZ5KCzWWTJ/MiFSxaQ2GJLKFolIldbKdI8l9MsS9DRsulA6ZZ5AYbnZ+ 545UBQdIzq8BpgQhtQFEb8lL1QEccX+o7QNdSw0wOd+MFQiF6KhgM5HpsA2AOL2HGU/M kYL75COpOWEAQs/innmVqdmTR7Tz+W0iRIU9Ef9BejJMPPBdGhfgLyeGuBZiKt5eBqgi eD0FyQwEDJufVKTlO2lEZVY9oBMnlGO91a/FX91VoeKHlhgRiuhZujDzjvJdgxEMKdGj /VFGeATEl/Fod4DFqcu5nd5a14iglyyQRdoMed2oMEspYaWyQRFWgIHuT0lCq868UZ4I eWBw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=hLTD2Uw33ruzT4aIF9v59VNMUBom9/69Xaztq/CP3Xc=; b=o0393Zeb4ozwsO4I3IPE/mIKlsxZge7N/Ulogp0EUhEJ/uENKP7hZEQBbhA+j/RmFp 6mjFDgj3u8pZ/6FVzDSlO8WDTL5CTxBZ4QhcwHr6vuADPDHfsugEN2gwtqoH32qbmYfr t2/Pt3IbUKSevDUbqh1HP2+NHsvacqVzlGrBXaH1SA8n2pEBPHVpWOUTzwjYHLnZrwSX WCS3XoYYQHwODpkvkEhENodmy7m+MZlTjzdtmOR5Z7FA9R8Q5lubUYlE070L//sckp8b nfdkdxRz5fo+f4ia3XBekMPoLbg3WON4khXOSiY0z8riFGbvieT5lzc5D5hrFgirkXXx U4KQ== X-Gm-Message-State: APjAAAV36zwLtM05UUuZTMdstDl1BRljxYtIGNkqbPgAqrIeTiHJeZr8 0kEOswpRQK92JpnQY6x0iEUnGh5byzE= X-Google-Smtp-Source: APXvYqzSURFiA5Jm5hCzVvwO2W37gP6y7v2Yuz6L9La3oJ2wX9czRKXd/aUrHf4ia66e1lWA33oIXA== X-Received: by 2002:a17:90a:17c4:: with SMTP id q62mr119990873pja.104.1564507788792; Tue, 30 Jul 2019 10:29:48 -0700 (PDT) Received: from nebulus.mtv.corp.google.com ([2620:15c:211:200:5404:91ba:59dc:9400]) by smtp.gmail.com with ESMTPSA id o129sm39856293pfg.1.2019.07.30.10.29.47 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 30 Jul 2019 10:29:48 -0700 (PDT) From: Mark Salyzyn To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, Mark Salyzyn , Miklos Szeredi , Jonathan Corbet , Vivek Goyal , "Eric W . Biederman" , Amir Goldstein , Randy Dunlap , Stephen Smalley , linux-unionfs@vger.kernel.org, linux-doc@vger.kernel.org Subject: [PATCH v12 4/5] overlayfs: internal getxattr operations without sepolicy checking Date: Tue, 30 Jul 2019 10:29:01 -0700 Message-Id: <20190730172904.79146-5-salyzyn@android.com> X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog In-Reply-To: <20190730172904.79146-1-salyzyn@android.com> References: <20190730172904.79146-1-salyzyn@android.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Check impure, opaque, origin & meta xattr with no sepolicy audit (using __vfs_getxattr) since these operations are internal to overlayfs operations and do not disclose any data. This became an issue for credential override off since sys_admin would have been required by the caller; whereas would have been inherently present for the creator since it performed the mount. This is a change in operations since we do not check in the new ovl_do_vfs_getxattr function if the credential override is off or not. Reasoning is that the sepolicy check is unnecessary overhead, especially since the check can be expensive. Because for override credentials off, this affects _everyone_ that underneath performs private xattr calls without the appropriate sepolicy permissions and sys_admin capability. Providing blanket support for sys_admin would be bad for all possible callers. For the override credentials on, this will affect only the mounter, should it lack sepolicy permissions. Not considered a security problem since mounting by definition has sys_admin capabilities, but sepolicy contexts would still need to be crafted. It should be noted that there is precedence, __vfs_getxattr is used in other filesystems for their own internal trusted xattr management. Signed-off-by: Mark Salyzyn Cc: Miklos Szeredi Cc: Jonathan Corbet Cc: Vivek Goyal Cc: Eric W. Biederman Cc: Amir Goldstein Cc: Randy Dunlap Cc: Stephen Smalley Cc: linux-unionfs@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: kernel-team@android.com --- v12 - rebase v11 - switch name to ovl_do_vfs_getxattr, fortify comment v10 - added to patch series --- fs/overlayfs/namei.c | 12 +++++++----- fs/overlayfs/overlayfs.h | 2 ++ fs/overlayfs/util.c | 24 +++++++++++++++--------- 3 files changed, 24 insertions(+), 14 deletions(-) diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index 9702f0d5309d..a4a452c489fa 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -106,10 +106,11 @@ int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) { - int res, err; + ssize_t res; + int err; struct ovl_fh *fh = NULL; - res = vfs_getxattr(dentry, name, NULL, 0); + res = ovl_do_vfs_getxattr(dentry, name, NULL, 0); if (res < 0) { if (res == -ENODATA || res == -EOPNOTSUPP) return NULL; @@ -123,7 +124,7 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) if (!fh) return ERR_PTR(-ENOMEM); - res = vfs_getxattr(dentry, name, fh, res); + res = ovl_do_vfs_getxattr(dentry, name, fh, res); if (res < 0) goto fail; @@ -141,10 +142,11 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) return NULL; fail: - pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res); + pr_warn_ratelimited("overlayfs: failed to get origin (%zi)\n", res); goto out; invalid: - pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh); + pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", + (int)res, fh); goto out; } diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index ab3d031c422b..9d26d8758513 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -205,6 +205,8 @@ int ovl_want_write(struct dentry *dentry); void ovl_drop_write(struct dentry *dentry); struct dentry *ovl_workdir(struct dentry *dentry); const struct cred *ovl_override_creds(struct super_block *sb); +ssize_t ovl_do_vfs_getxattr(struct dentry *dentry, const char *name, void *buf, + size_t size); struct super_block *ovl_same_sb(struct super_block *sb); int ovl_can_decode_fh(struct super_block *sb); struct dentry *ovl_indexdir(struct super_block *sb); diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index f5678a3f8350..f80b95423043 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -40,6 +40,12 @@ const struct cred *ovl_override_creds(struct super_block *sb) return override_creds(ofs->creator_cred); } +ssize_t ovl_do_vfs_getxattr(struct dentry *dentry, const char *name, void *buf, + size_t size) +{ + return __vfs_getxattr(dentry, d_inode(dentry), name, buf, size); +} + struct super_block *ovl_same_sb(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; @@ -537,9 +543,9 @@ void ovl_copy_up_end(struct dentry *dentry) bool ovl_check_origin_xattr(struct dentry *dentry) { - int res; + ssize_t res; - res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0); + res = ovl_do_vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0); /* Zero size value means "copied up but origin unknown" */ if (res >= 0) @@ -550,13 +556,13 @@ bool ovl_check_origin_xattr(struct dentry *dentry) bool ovl_check_dir_xattr(struct dentry *dentry, const char *name) { - int res; + ssize_t res; char val; if (!d_is_dir(dentry)) return false; - res = vfs_getxattr(dentry, name, &val, 1); + res = ovl_do_vfs_getxattr(dentry, name, &val, 1); if (res == 1 && val == 'y') return true; @@ -837,13 +843,13 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir) /* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */ int ovl_check_metacopy_xattr(struct dentry *dentry) { - int res; + ssize_t res; /* Only regular files can have metacopy xattr */ if (!S_ISREG(d_inode(dentry)->i_mode)) return 0; - res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0); + res = ovl_do_vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0); if (res < 0) { if (res == -ENODATA || res == -EOPNOTSUPP) return 0; @@ -852,7 +858,7 @@ int ovl_check_metacopy_xattr(struct dentry *dentry) return 1; out: - pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res); + pr_warn_ratelimited("overlayfs: failed to get metacopy (%zi)\n", res); return res; } @@ -878,7 +884,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value, ssize_t res; char *buf = NULL; - res = vfs_getxattr(dentry, name, NULL, 0); + res = ovl_do_vfs_getxattr(dentry, name, NULL, 0); if (res < 0) { if (res == -ENODATA || res == -EOPNOTSUPP) return -ENODATA; @@ -890,7 +896,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value, if (!buf) return -ENOMEM; - res = vfs_getxattr(dentry, name, buf, res); + res = ovl_do_vfs_getxattr(dentry, name, buf, res); if (res < 0) goto fail; } -- 2.22.0.770.g0f2c4a37fd-goog