From patchwork Wed Nov 20 18:24:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 11254629 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 E66F9109A for ; Wed, 20 Nov 2019 18:25:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE19D20878 for ; Wed, 20 Nov 2019 18:25:00 +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="eK7TtBsT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728453AbfKTSY4 (ORCPT ); Wed, 20 Nov 2019 13:24:56 -0500 Received: from mail-pl1-f196.google.com ([209.85.214.196]:39955 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728391AbfKTSYz (ORCPT ); Wed, 20 Nov 2019 13:24:55 -0500 Received: by mail-pl1-f196.google.com with SMTP id f9so151004plr.7 for ; Wed, 20 Nov 2019 10:24:53 -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=o2+igEOnCXCoZoiAJpf5HHbPvlBNpJqwdgFjMnknAbY=; b=eK7TtBsTTOswuydlQGQCX2MZgOEiLqA+PiWtbN5oI92q3BbkVN+U1v9tQPxo4a+nA8 qXLloGoiSXBYGYBi1uoMZ9N5DZHRylT68PwWBNEaIUgs7+98Ke7UlxU8LxMTzTtQ4RVF 79dPyl/ktVGqSBYNPDrSk/g29ZW5hl/rqcLDAWdxzeA4jxFWBc4WYKg6O5ya1geXHC2B AmqWoym6YUG0n6A4ZdOF2sm3so8h4uvd0D+vOHQx54Tl5ln2OQLTkjyiq/sHLTm/rH8a AhVHmKQgVa/zVc+Ussn1SSXr0zkUT4E/hsONWHKxEURZP+UKb8GJP0BFqBaHehqb40jK bAHQ== 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=o2+igEOnCXCoZoiAJpf5HHbPvlBNpJqwdgFjMnknAbY=; b=dKgwqEvj2zUtJRWTEtEOlQVi4S5DEzM8uwmva56S5F3vVGj5ZbEzdK2lAUYvRR8BoV BmEgYMyqxp+UMO24qg6CFfrTk51zr+nDQRbLZ/p5a1Jua/h86D+zZEEFnNWn+YQvKhiq H6uo6z0JS1I+NmRmENYNQFu+YcYSIgsGFNUeQrNKUcKRsw3Bf2iaxLgRtYgBMeS03xCp 1bMNv5fyn6LztGl+SUgS0qgQSYKeFXmCWgUDA0juqY20TJ7i5pASnA292DSa9RDuqMmf mEWJTkQ97wdjCm0kQ3yzydhkccUnOjPSXH95NGXKXLsgTtZVrlwwn4UmfquZYBDUbn9D ZxmQ== X-Gm-Message-State: APjAAAVWsKxaJ/WfZWSOsKgWi7GooItv2Boa3JHHRbcseIJ3ncCQ0zQJ 0Csg0r7v6OYhSFL5fYj3Sf6pMSB1pMg= X-Google-Smtp-Source: APXvYqz/nFa1LIb2dXpleNzDUkBRlPW/dFm2GFWU8U4h6SWYn5eD5w9bHRly15ufQHluyuVeanTRjA== X-Received: by 2002:a17:90a:f84:: with SMTP id 4mr5695411pjz.110.1574274292981; Wed, 20 Nov 2019 10:24:52 -0800 (PST) Received: from vader.thefacebook.com ([2620:10d:c090:180::1a46]) by smtp.gmail.com with ESMTPSA id q34sm7937866pjb.15.2019.11.20.10.24.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Nov 2019 10:24:52 -0800 (PST) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org Cc: Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [RFC PATCH v3 02/12] fs: add O_ALLOW_ENCODED open flag Date: Wed, 20 Nov 2019 10:24:22 -0800 Message-Id: X-Mailer: git-send-email 2.24.0 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 3d40771e8e7c..407e663dff4a 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) @@ -1031,7 +1037,7 @@ 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 671c3c1a3425..737d9f05b095 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2978,6 +2978,10 @@ 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 d019df946cb2..0dc6fa93f7cb 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -9,7 +9,7 @@ (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) #ifndef force_o_largefile #define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T)) 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)