From patchwork Thu Apr 1 06:51:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 12177343 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 51CF7C43616 for ; Thu, 1 Apr 2021 06:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 268DC61106 for ; Thu, 1 Apr 2021 06:52:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233167AbhDAGvl (ORCPT ); Thu, 1 Apr 2021 02:51:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232661AbhDAGvc (ORCPT ); Thu, 1 Apr 2021 02:51:32 -0400 Received: from mail-pg1-x52b.google.com (mail-pg1-x52b.google.com [IPv6:2607:f8b0:4864:20::52b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9CCBC0613E6 for ; Wed, 31 Mar 2021 23:51:31 -0700 (PDT) Received: by mail-pg1-x52b.google.com with SMTP id h25so966196pgm.3 for ; Wed, 31 Mar 2021 23:51:31 -0700 (PDT) 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=JwuTEoZ8l+sPh9rkipyaeTuQjepYsk3sjw+UvHwaOUE=; b=JQivmxD/gfavpSDXOqWtr65zP2oQ9kXrPaePJ+u66/mU7QX0cUBcDmcWqjc2o0x/v4 7WUvnePJM2sSaRjSEBgcQTCoFag8+s9B1ehUlr4ksO5f6doJrh5V6SJZ7vrdkyEgWiFO 0YyL0T6065Tu4loo2JRjpSagb/5hA074JSruv0Socf3q6FDELby0swo8j3lU20tLUHpX 0CXhrFELg2/I0i0BjdwaRgYjS6MKD4RNb4kvjlppZ7hTzzx5u8mef2zVZqvsMTTAcnQ/ UQJgTlc9aT69FdqN24JFegSjahpQL4HitczdiFNWVpTYswYYBHNOl47OcgULtOcETchy aapQ== 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=JwuTEoZ8l+sPh9rkipyaeTuQjepYsk3sjw+UvHwaOUE=; b=uPYIPbAGkhfNtvB81zazHpuZH7Y/wBjLtXa92uERQKF1RPPAwQAcnWL11kOY/iFEUU +SrEYUn89tjNKruqGaaWOE0vROkrjAlFYWY3Tf7YQxsC9b7fh2APB9GlhjCYzu9R/yMn NDx8OMG1M9lvE/HEKro5J69gciLDbJGa0of2MZ+J2jRADjMrBgoVA/b9gu96mPKQfkef Wi5UZqi9IoMVMwgiafrmbNut33K/Djhk0FA1+9b5UEz8f1QvZZaCTct+KjnuFrmxX2nx 8nGzG0ODWzauutn4Bq+AQgNi0Ah+i05MMKV6m21iY9RFQmO5KJiAZECkcAF3C4QQ3R4g Hh4g== X-Gm-Message-State: AOAM533XPSSeZzb08DPOw14KH/NA5vCYx+ykrJw0wtyL2ZXkrqgWDey6 obNJL93p7+OqjAg91BDSKw2Qow== X-Google-Smtp-Source: ABdhPJx/c6CSE14N+hW/gHjqWkYv2Yk62p0FOVhaK5JnZ/5sCEueNB9AT/wxnjGJp8DAV9fYSZJREw== X-Received: by 2002:a63:cd01:: with SMTP id i1mr6205004pgg.262.1617259891308; Wed, 31 Mar 2021 23:51:31 -0700 (PDT) Received: from relinquished.tfbnw.net ([2620:10d:c090:400::5:3734]) by smtp.gmail.com with ESMTPSA id kk6sm4158345pjb.51.2021.03.31.23.51.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Mar 2021 23:51:30 -0700 (PDT) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig Cc: Linus Torvalds , Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v9 2/9] fs: add O_ALLOW_ENCODED open flag Date: Wed, 31 Mar 2021 23:51:07 -0700 Message-Id: <8bde1d854c568c55196cdc0af9ea9144f52024f8.1617258892.git.osandov@fb.com> X-Mailer: git-send-email 2.31.1 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. Reviewed-by: Josef Bacik Signed-off-by: Omar Sandoval --- 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..0feb31faaefa 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 0100000000 #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 dfc72f15be7f..eca4eb008194 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -31,7 +31,8 @@ #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) { @@ -50,6 +51,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg) if (!inode_owner_or_capable(file_mnt_user_ns(filp), 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) @@ -1043,7 +1049,7 @@ 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 216f16e74351..7160e19a9f21 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2998,6 +2998,10 @@ static int may_open(struct user_namespace *mnt_userns, const struct path *path, if (flag & O_NOATIME && !inode_owner_or_capable(mnt_userns, 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 766fcd973beb..2cd6a9185d4c 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)