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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1963CCA489 for ; Tue, 7 Jun 2022 21:27:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379722AbiFGV0A (ORCPT ); Tue, 7 Jun 2022 17:26:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376813AbiFGU2L (ORCPT ); Tue, 7 Jun 2022 16:28:11 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD5D11D92CA; Tue, 7 Jun 2022 11:33:14 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id A7F1DCE240B; Tue, 7 Jun 2022 18:33:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F1FAC385A2; Tue, 7 Jun 2022 18:33:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1654626791; bh=Pm1sdPAeGW7S0pQyTrq8Rdh0/AYBc4BFWlu2G/4YV0M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=T25DMwlFjKmsg3ot7bubjOSzselnbXcIqSZwq7H2Qm4EhN/6luxxQpQ08+hotAlKU O+ik5k/xD8p59dpj82xyUhYlWA91XW6lVn65PcsfTQbpA72gTOcd169UVA/Xc3u6UO et447AIGklN7jRwUZAupJFZ6YuvvWeSc17Ayepoo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jacky Li , Peter Gonda , Tom Lendacky , Herbert Xu , Sasha Levin Subject: [PATCH 5.17 504/772] crypto: ccp - Fix the INIT_EX data file open failure Date: Tue, 7 Jun 2022 19:01:36 +0200 Message-Id: <20220607165003.831479908@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220607164948.980838585@linuxfoundation.org> References: <20220607164948.980838585@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jacky Li [ Upstream commit 05def5cacfa0bd5ba380116046747da07ff5bd78 ] There are 2 common cases when INIT_EX data file might not be opened successfully and fail the sev initialization: 1. In user namespaces, normal user tasks (e.g. VMM) can change their current->fs->root to point to arbitrary directories. While init_ex_path is provided as a module param related to root file system. Solution: use the root directory of init_task to avoid accessing the wrong file. 2. Normal user tasks (e.g. VMM) don't have the privilege to access the INIT_EX data file. Solution: open the file as root and restore permissions immediately. Fixes: 3d725965f836 ("crypto: ccp - Add SEV_INIT_EX support") Signed-off-by: Jacky Li Reviewed-by: Peter Gonda Acked-by: Tom Lendacky Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- drivers/crypto/ccp/sev-dev.c | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 6ab93dfd478a..3aefb177715e 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -23,6 +23,7 @@ #include #include #include +#include #include @@ -170,6 +171,31 @@ static void *sev_fw_alloc(unsigned long len) return page_address(page); } +static struct file *open_file_as_root(const char *filename, int flags, umode_t mode) +{ + struct file *fp; + struct path root; + struct cred *cred; + const struct cred *old_cred; + + task_lock(&init_task); + get_fs_root(init_task.fs, &root); + task_unlock(&init_task); + + cred = prepare_creds(); + if (!cred) + return ERR_PTR(-ENOMEM); + cred->fsuid = GLOBAL_ROOT_UID; + old_cred = override_creds(cred); + + fp = file_open_root(&root, filename, flags, mode); + path_put(&root); + + revert_creds(old_cred); + + return fp; +} + static int sev_read_init_ex_file(void) { struct sev_device *sev = psp_master->sev_data; @@ -181,7 +207,7 @@ static int sev_read_init_ex_file(void) if (!sev_init_ex_buffer) return -EOPNOTSUPP; - fp = filp_open(init_ex_path, O_RDONLY, 0); + fp = open_file_as_root(init_ex_path, O_RDONLY, 0); if (IS_ERR(fp)) { int ret = PTR_ERR(fp); @@ -217,7 +243,7 @@ static void sev_write_init_ex_file(void) if (!sev_init_ex_buffer) return; - fp = filp_open(init_ex_path, O_CREAT | O_WRONLY, 0600); + fp = open_file_as_root(init_ex_path, O_CREAT | O_WRONLY, 0600); if (IS_ERR(fp)) { dev_err(sev->dev, "SEV: could not open file for write, error %ld\n", -- 2.35.1