From patchwork Thu Mar 26 14:51:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marcelo Henrique Cerri X-Patchwork-Id: 1262059 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=canonical.com Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 48p7Gl2BvGz9sSb; Fri, 27 Mar 2020 01:51:27 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1jHTqt-0000do-Mj; Thu, 26 Mar 2020 14:51:23 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jHTqr-0000d5-Ge for kernel-team@lists.ubuntu.com; Thu, 26 Mar 2020 14:51:21 +0000 Received: from mail-qv1-f69.google.com ([209.85.219.69]) by youngberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jHTqr-0004oz-5V for kernel-team@lists.ubuntu.com; Thu, 26 Mar 2020 14:51:21 +0000 Received: by mail-qv1-f69.google.com with SMTP id q5so1712249qvr.13 for ; Thu, 26 Mar 2020 07:51:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=iCNYrkw83OwCYv1aXSj4SyDsSUV8AwJqSCe4a9xA9Wg=; b=iw+2ZMv30Y26AeuFMMPPAXUAV9SuKXewu7nhs5hZLp5YrD3eyZZT7iK8Xnt9LSrN+F gfKUni6tFIrmdYldSAvkrrlDXOyK13trnO92qywST9N+HrdPsjOmochNBU+Rg4vVnIPX a1+lfss8O8dYNEhgXZZ1LrNu521ymJqHDMa6jteJ1DZkSP/JqLPKFBjRJHNe7CCuDhFj IEwbqVosU0xRVOjMAs3vgRW3Cec6RsFMDIA7PRdyxqxd3F7cwc8AQlvAY0Ex4fKI3aCU ncBrTN/11t37ZqC4+OUL0B4aJ6F6DlOR+c5V4lbvSDHw9LOrXOnsY8CAJImyPvDyJCWT O6vw== X-Gm-Message-State: ANhLgQ1B7BzFf2ICisZhlZcVsgyP1JyifBIOKnMtFCPE9DGtt9ykzvRu 7jhMyvEQ8Hx8UVPbLxnhBEaSBd9Dcka3pV0mMoizA+6ykmZ1+AvXbgoWkhXwc5HAWPXpyfJqtJ2 +t2T6ZY8m3GEayH2B89yM+8h5MFDGH4AHu8/oxjKh X-Received: by 2002:aed:35b1:: with SMTP id c46mr8510423qte.74.1585234279817; Thu, 26 Mar 2020 07:51:19 -0700 (PDT) X-Google-Smtp-Source: ADFU+vtq6IXpXBR+gLTLxkspawD3Ljfo78fSAakds/SIcokP5AkDz9ukd0JNPbMeNGxd608ry3wQrA== X-Received: by 2002:aed:35b1:: with SMTP id c46mr8510396qte.74.1585234279466; Thu, 26 Mar 2020 07:51:19 -0700 (PDT) Received: from gallifrey.lan ([2804:14c:4e6:352:ed06:bdde:808e:a76f]) by smtp.gmail.com with ESMTPSA id c12sm1751440qtb.49.2020.03.26.07.51.17 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 07:51:18 -0700 (PDT) From: Marcelo Henrique Cerri To: kernel-team@lists.ubuntu.com Subject: [{eoan, focal}:linux-azure][PATCH] UBUNTU: SAUCE: overlayfs: internal getxattr operations without sepolicy checking Date: Thu, 26 Mar 2020 11:51:11 -0300 Message-Id: <20200326145111.1798-3-marcelo.cerri@canonical.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200326145111.1798-1-marcelo.cerri@canonical.com> References: <20200326145111.1798-1-marcelo.cerri@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Mark Salyzyn BugLink: https://bugs.launchpad.net/bugs/1864669 [Based on v15: https://lore.kernel.org/patchwork/patch/1148514/] 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 Cc: linux-security-module@vger.kernel.org v15 - revert to v13 as xattr_gs_args was rejected. - move ovl_do_wrapper from util.c to inline in overlayfs.h v14 - rebase to use xattr_gs_args. v13 - rebase to use __vfs_getxattr flags option v12 - rebase v11 - switch name to ovl_do_vfs_getxattr, fortify comment v10 - added to patch series [marcelo.cerri@canonical.com: Adjusted __vfs_getxattr() args and removed XATTR_NOSECURITY] Signed-off-by: Marcelo Henrique Cerri --- fs/overlayfs/namei.c | 12 +++++++----- fs/overlayfs/overlayfs.h | 7 +++++++ fs/overlayfs/util.c | 18 +++++++++--------- 3 files changed, 23 insertions(+), 14 deletions(-) diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index f47c591402d7..126a93d6a5ab 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 ca10974b9f44..94f840eb7d7d 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -212,6 +212,13 @@ static inline bool ovl_open_flags_need_copy_up(int flags) return ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC)); } +static inline 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); +} + /* util.c */ int ovl_want_write(struct dentry *dentry); void ovl_drop_write(struct dentry *dentry); diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index e78d873acc3e..40b12d153c52 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -550,9 +550,9 @@ 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) @@ -563,13 +563,13 @@ 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; @@ -850,13 +850,13 @@ 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; @@ -865,7 +865,7 @@ 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; } @@ -891,7 +891,7 @@ 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; @@ -903,7 +903,7 @@ 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; }