From patchwork Mon Apr 26 19:06:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 12224929 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,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 91F4DC43460 for ; Mon, 26 Apr 2021 19:06:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6616460BBB for ; Mon, 26 Apr 2021 19:06:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240056AbhDZTHV (ORCPT ); Mon, 26 Apr 2021 15:07:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240014AbhDZTHL (ORCPT ); Mon, 26 Apr 2021 15:07:11 -0400 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB64CC061574 for ; Mon, 26 Apr 2021 12:06:25 -0700 (PDT) Received: by mail-pj1-x102e.google.com with SMTP id f6-20020a17090a6546b029015088cf4a1eso5862333pjs.2 for ; Mon, 26 Apr 2021 12:06:25 -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=NgT56OeZMtHDF6pkRlLefN/K3Ae4GRjJeZyqXlRwP5k=; b=TrAQNjNPOEOiBSiPil19xi9Kckrg2XCOtr9sAsN6phy5iQuNLcrlIO1VHalknXSz0x Bve7Ay6zCo8MC/k8rIfuLYu52bkS6WtN4mO21m0chEabbCTienaGUBUbsJUiVEeBq/Yu z1weH7PGsiDuv2/C4dkJ64moP0NLyN7/2CTRJUfI/HXTFZ4gdL9m2/4fSAbuvhTKuE2R P4jEEVpD6hsmIfzZp8o0b+6MzjDQPZS7H2cp7TI8EeO71gDkV76QMeaGtCB3L+S/YwUC JbQsAwGDcI4azMkkdQp9EOKYowZsq2BEeRNcYTkub1x5QPLFFVb0dAUjAZhGZy+JnhKQ dMfA== 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=NgT56OeZMtHDF6pkRlLefN/K3Ae4GRjJeZyqXlRwP5k=; b=p/xDxTsf78fV5fB6NT0NcJVtLPK7sagOMHsqZttwhKGHAdLMgumYYrnVDcZglIlLKV v32F4CsDxQ9tetWyoe2z9BtBvjIopOZmwfsGSUNswXa4kSZLEv9gBC9O0FlTPeBxAZdM yK7qN8P7ao93vFMGfctROK97+1OBzJG8AxUAXp8SWte8iuqTfx9X37VzYf46TgAJ1ajk U29+L27FwMbfnQfVRUlC4hhi78reiRmTp2JGyytf5WGXYDQF+vbqsMoTsLDc6/QVFthv 1dggKy6bJZln7kjFy8yW0qe/u8e1AE8dFsq4uW4wygClEAH/VGCcPym9R7VPQzek7Y26 +J0A== X-Gm-Message-State: AOAM530zZ8h9VevA5xPrIB5gwfcuslHzmQUeay7tYyNgtKykvXX0lL/c gU+UVF9iiUcYAHh9BBkJmcbmlA== X-Google-Smtp-Source: ABdhPJw7tv00Z67MNpPnOz1hnXduWwtTrkRTVyF+Fq1SJHg2GEz9nBAbNzUcU5M3KVDpynr8d69mOg== X-Received: by 2002:a17:90a:a781:: with SMTP id f1mr23560054pjq.57.1619463985230; Mon, 26 Apr 2021 12:06:25 -0700 (PDT) Received: from relinquished.tfbnw.net ([2620:10d:c090:400::5:f06a]) by smtp.gmail.com with ESMTPSA id lx11sm331745pjb.27.2021.04.26.12.06.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Apr 2021 12:06:24 -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 RESEND v9 2/9] fs: add O_ALLOW_ENCODED open flag Date: Mon, 26 Apr 2021 12:06:05 -0700 Message-Id: <61323972c3d5daf5f39c9034c58c0e4d7e651aac.1619463858.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 48a2f288e802..986bd8312171 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3000,6 +3000,10 @@ 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)