From patchwork Fri Aug 21 07:38:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 11728425 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 63DDD739 for ; Fri, 21 Aug 2020 07:39:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 381B22078D for ; Fri, 21 Aug 2020 07:39:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="MHC+Q9YS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728149AbgHUHjM (ORCPT ); Fri, 21 Aug 2020 03:39:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36942 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728123AbgHUHi4 (ORCPT ); Fri, 21 Aug 2020 03:38:56 -0400 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4F9FC061387 for ; Fri, 21 Aug 2020 00:38:56 -0700 (PDT) Received: by mail-pj1-x1044.google.com with SMTP id j13so464317pjd.4 for ; Fri, 21 Aug 2020 00:38:56 -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=Hunj461oh9Q7J38eWlWUsMBSMG0f/jDb/B+wMlt2xiA=; b=MHC+Q9YS8W33sMSsIbwDX2ubNCHI0/zr/tTwDkHTw2+yRFZV5SKeYg15UU1Rh1fFBd ZG2vd9Jsn7SI1cCdUwtSeAwChS9bpSIA4At0G1HxE2GRXpDVQLcYAjqcTZV6qufvRfvO 1KvNTgv2EeGEfN7GHDIYT7lTB4O3icdcbJKSzEr3Q112Or/e9+xt6102h7N5BqIzzLxT jEkB9IjQxKiwKPkkioOA9zbtVE+VI+AvHKfMr3T3+JtNuvnq+UC4b+mkh51WN+K7E5cQ l067YQm2/pf2ItQojV4rmIXQBd/3mmKMwZ2Lf3m0G09d3fMI6gnOyAPoYMzpk/79Ri7o DbFw== 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=Hunj461oh9Q7J38eWlWUsMBSMG0f/jDb/B+wMlt2xiA=; b=rlOUbrCrE7H62yHtXpWk4vpOA5X1MeT2Ig1uZ4eut0DBeW36tw5vhX5mSOK4yD7oun enTJ76tczv9DTPbnt/uOuSyMUtQ1S2Vi4MPJLM6SBV2J75xaDLx4X9B7dFhIQjbvahj9 lncd/qYzZE57TGNN6aLa+5xZBmtagftm7aZtzzr/1ajKqjsFD2181k5olojHQcQ6BPJc iv/fnrCIG2Ut3ADD9rnJPL4VEmPwhL0TlxbN/kJaBQTJSDsYHR02P4MWVoTL2V9rNRGY 64MV9RvF08Qv/pCwRkg9rAlGNKb02qLgyA9RyEK7dyZqEEUgJHSdW0pfEioh9kvTZpb1 wGHg== X-Gm-Message-State: AOAM531lLdZuQTYmhkhNnj5xQQzsLjNKDmN3W6UCv66eMpC2q+uL3HTQ v9aaIvi7Hb9qwsB7picTumNzT3P0S/uJiw== X-Google-Smtp-Source: ABdhPJwlsPmBRjb1n1dkBd+DorJyEILG58tSCYf6h+j8+2UDVq9tBeyNGexYM1D3ZPKo8ebAZdk3Dg== X-Received: by 2002:a17:90b:808:: with SMTP id bk8mr1353159pjb.63.1597995535600; Fri, 21 Aug 2020 00:38:55 -0700 (PDT) Received: from exodia.tfbnw.net ([2620:10d:c090:400::5:f2a4]) by smtp.gmail.com with ESMTPSA id t10sm1220867pgp.15.2020.08.21.00.38.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2020 00:38:54 -0700 (PDT) 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 v5 2/9] fs: add O_ALLOW_ENCODED open flag Date: Fri, 21 Aug 2020 00:38:33 -0700 Message-Id: X-Mailer: git-send-email 2.28.0 In-Reply-To: References: MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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; it should probably be used with O_CLOEXEC in most cases. 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 --- 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 03ce20e5ad7d..1188b27002b3 100644 --- a/arch/parisc/include/uapi/asm/fcntl.h +++ b/arch/parisc/include/uapi/asm/fcntl.h @@ -22,6 +22,7 @@ #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 2e4c0fa2074b..a9daebd41d03 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) @@ -1033,7 +1039,7 @@ 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 e99e2a9da0f7..7fc5ed73078c 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2889,6 +2889,10 @@ 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 7bcdcf4f6ab2..670939ea3c80 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_NDELAY | __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)