From patchwork Fri Jan 22 20:46:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 12040631 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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 0F44AC433DB for ; Fri, 22 Jan 2021 21:16:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDC7323B09 for ; Fri, 22 Jan 2021 21:16:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730161AbhAVVPz (ORCPT ); Fri, 22 Jan 2021 16:15:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729468AbhAVUtW (ORCPT ); Fri, 22 Jan 2021 15:49:22 -0500 Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CB40FC061352 for ; Fri, 22 Jan 2021 12:47:23 -0800 (PST) Received: by mail-pl1-x629.google.com with SMTP id h15so1482992pli.8 for ; Fri, 22 Jan 2021 12:47:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=ebBFLla+oq6Fu8NNd3NcGHArvFeQ09WYnlC9IkZrxIc=; b=CRAF4UcnAm/BtIvVRfBo4+C4xSKqe1kvd5ymqv1SnomF7F+lPPFW3nV2U014DKZ8/m gaInPQXQnY7Kuk4NQ/xioc90wp6AhyUMUn2STCF1ZMP66n9zzOCuUrXhU/I6xofMKjSl 2fVQQHKy7GEdsijw6IeX/rSTujpvHskGJ0arnytgw8N+ZDxHidc8PY/BAhqaJO+5iAKM h6FD00W5lpR+pXoQGg8T4sgCRCC0hytnlCibvHPRdCd9G2gIy5mMvkmOf8pt2dNwIKTC FJ9qNFyTLo0RLmDkV81EarSPHAGWoykD2mriPKAF6HO2j1Eo3i0PbHFhTG/6gnyTd+dQ lLvQ== 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=ebBFLla+oq6Fu8NNd3NcGHArvFeQ09WYnlC9IkZrxIc=; b=WJzIctJHpY8oN4wrZQ0Gj27QUqsWCIvSVDBNRymDOEuq64goERTc9VG6OyUqcu+Vqg O40jjkzCHTvElZpZcP5nZSQ5lC0lm8ya7ZkgHXdnAch71F0H6GWz30/xy4QpjIIALKzU NNDHGb1np1cWJxOQiWzPSqy3GR40gQ5APSUPQAYu7Mnl3UwS7Jkq461s1TviFCdyJUab GCpNBbwoPrg4QuZ6K7zFw+ghquIo1rjnM50dc2nYXHjoSTuiB839yb8VN+ihWs2+01MR 8L9gv5ijylK0+vjhqr9mPmVZ2h3Q+G9N4r4WrSCmqiZgb34bhIJFbyeyI+CDrEnoGEiU QMrg== X-Gm-Message-State: AOAM53214kzFPSdKvIyJAWBwmpgDsuNn+jzsCVAu28foR9YsO0glqTcF EVUi3MuWsdEEf8JqOcHnHc3DYg== X-Google-Smtp-Source: ABdhPJzlU6VoXtH6Y1tNDhS0ekWFfZXU5C+5K1BPn9WzwPAHc8pTtFnqs9nco3ZT5ZQORSBVeehdnQ== X-Received: by 2002:a17:90b:78f:: with SMTP id l15mr214949pjz.234.1611348443355; Fri, 22 Jan 2021 12:47:23 -0800 (PST) Received: from relinquished.tfbnw.net ([2620:10d:c090:400::5:ea88]) by smtp.gmail.com with ESMTPSA id j18sm4092900pfc.99.2021.01.22.12.47.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Jan 2021 12:47:22 -0800 (PST) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig Cc: Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v7 02/10] fs: add O_ALLOW_ENCODED open flag Date: Fri, 22 Jan 2021 12:46:49 -0800 Message-Id: <09988d880282a6ef0dd04d1fce7db1dbbd2d335c.1611346706.git.osandov@fb.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Omar Sandoval The upcoming RWF_ENCODED operation introduces some security concerns: 1. Compressed writes will pass arbitrary data to decompression algorithms in the kernel. 2. Compressed reads can leak truncated/hole punched data. Therefore, we need to require privilege for RWF_ENCODED. It's not possible to do the permissions checks at the time of the read or write because, e.g., io_uring submits IO from a worker thread. So, add an open flag which requires CAP_SYS_ADMIN. It can also be set and cleared with fcntl(). The flag is not cleared in any way on fork or exec. Note that the usual issue that unknown open flags are ignored doesn't really matter for O_ALLOW_ENCODED; if the kernel doesn't support O_ALLOW_ENCODED, then it doesn't support RWF_ENCODED, either. Signed-off-by: Omar Sandoval Reviewed-by: Josef Bacik --- arch/alpha/include/uapi/asm/fcntl.h | 1 + arch/parisc/include/uapi/asm/fcntl.h | 1 + arch/sparc/include/uapi/asm/fcntl.h | 1 + fs/fcntl.c | 10 ++++++++-- fs/namei.c | 4 ++++ include/linux/fcntl.h | 2 +- include/uapi/asm-generic/fcntl.h | 4 ++++ 7 files changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/alpha/include/uapi/asm/fcntl.h b/arch/alpha/include/uapi/asm/fcntl.h index 50bdc8e8a271..391e0d112e41 100644 --- a/arch/alpha/include/uapi/asm/fcntl.h +++ b/arch/alpha/include/uapi/asm/fcntl.h @@ -34,6 +34,7 @@ #define O_PATH 040000000 #define __O_TMPFILE 0100000000 +#define O_ALLOW_ENCODED 0200000000 #define F_GETLK 7 #define F_SETLK 8 diff --git a/arch/parisc/include/uapi/asm/fcntl.h b/arch/parisc/include/uapi/asm/fcntl.h index 03dee816cb13..72ea9bdf5f04 100644 --- a/arch/parisc/include/uapi/asm/fcntl.h +++ b/arch/parisc/include/uapi/asm/fcntl.h @@ -19,6 +19,7 @@ #define O_PATH 020000000 #define __O_TMPFILE 040000000 +#define O_ALLOW_ENCODED 100000000 #define F_GETLK64 8 #define F_SETLK64 9 diff --git a/arch/sparc/include/uapi/asm/fcntl.h b/arch/sparc/include/uapi/asm/fcntl.h index 67dae75e5274..ac3e8c9cb32c 100644 --- a/arch/sparc/include/uapi/asm/fcntl.h +++ b/arch/sparc/include/uapi/asm/fcntl.h @@ -37,6 +37,7 @@ #define O_PATH 0x1000000 #define __O_TMPFILE 0x2000000 +#define O_ALLOW_ENCODED 0x8000000 #define F_GETOWN 5 /* for sockets. */ #define F_SETOWN 6 /* for sockets. */ diff --git a/fs/fcntl.c b/fs/fcntl.c index 05b36b28f2e8..2c1f0580a497 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -30,7 +30,8 @@ #include #include -#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME) +#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME | \ + O_ALLOW_ENCODED) static int setfl(int fd, struct file * filp, unsigned long arg) { @@ -49,6 +50,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg) if (!inode_owner_or_capable(inode)) return -EPERM; + /* O_ALLOW_ENCODED can only be set by superuser */ + if ((arg & O_ALLOW_ENCODED) && !(filp->f_flags & O_ALLOW_ENCODED) && + !capable(CAP_SYS_ADMIN)) + return -EPERM; + /* required for strict SunOS emulation */ if (O_NONBLOCK != O_NDELAY) if (arg & O_NDELAY) @@ -1035,7 +1041,7 @@ static int __init fcntl_init(void) * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY * is defined as O_NONBLOCK on some platforms and not on others. */ - BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ != + BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) | __FMODE_EXEC | __FMODE_NONOTIFY)); diff --git a/fs/namei.c b/fs/namei.c index 78443a85480a..73b925b133a0 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2892,6 +2892,10 @@ static int may_open(const struct path *path, int acc_mode, int flag) if (flag & O_NOATIME && !inode_owner_or_capable(inode)) return -EPERM; + /* O_ALLOW_ENCODED can only be set by superuser */ + if ((flag & O_ALLOW_ENCODED) && !capable(CAP_SYS_ADMIN)) + return -EPERM; + return 0; } diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index 921e750843e6..dc66c557b7d0 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -10,7 +10,7 @@ (O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \ O_APPEND | O_NDELAY | O_NONBLOCK | __O_SYNC | O_DSYNC | \ FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \ - O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE) + O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_ALLOW_ENCODED) /* List of all valid flags for the how->upgrade_mask argument: */ #define VALID_UPGRADE_FLAGS \ diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index 9dc0bf0c5a6e..75321c7a66ac 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -89,6 +89,10 @@ #define __O_TMPFILE 020000000 #endif +#ifndef O_ALLOW_ENCODED +#define O_ALLOW_ENCODED 040000000 +#endif + /* a horrid kludge trying to make sure that this will fail on old kernels */ #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) #define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT)