From patchwork Tue Mar 16 19:42:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 12143701 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 C22CFC43619 for ; Tue, 16 Mar 2021 19:44:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ABD5D64E33 for ; Tue, 16 Mar 2021 19:44:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240572AbhCPToG (ORCPT ); Tue, 16 Mar 2021 15:44:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240533AbhCPTnh (ORCPT ); Tue, 16 Mar 2021 15:43:37 -0400 Received: from mail-pg1-x52e.google.com (mail-pg1-x52e.google.com [IPv6:2607:f8b0:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FE8EC061756 for ; Tue, 16 Mar 2021 12:43:34 -0700 (PDT) Received: by mail-pg1-x52e.google.com with SMTP id 16so16897288pgo.13 for ; Tue, 16 Mar 2021 12:43:34 -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=KYsaJGAN8p5DrzOlT18b0+bspU/AuNP29xRcOTFt+YA=; b=ct41l0ArdKLSRn1rPxdIi8UJxD2b2oOKdM4M2gxjVbYkowbPJArPqRcIO70sSZjSqN v01xAyaqBqcNz3hkSBoAdqZdz8OgXjBTsMHPqsa2fG3NUKN7o5dBVnvC/MywdSGVR3YQ MhM1HACZxMZlcWgWj7wi/U1MnFXsCly+kHDrYxWFe2/AxQPmJpxWtvh6TXTwF/MN+fBL 73VKQjPgw38uEy9hebnDoQ0qw0B916/SJA0hRV8N6vIrg3WaZRw+y9BvZVxrQHU9NNYD +wVXaMYdB0SCugqA7t+D9ALOAGvst/vcLB74oto4u7Zt1MMF8cKcuCNTYvaKRM6zt93w HhLA== 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=KYsaJGAN8p5DrzOlT18b0+bspU/AuNP29xRcOTFt+YA=; b=fWRZLUB9bMjRpTcpU+mtR9MwfZH5f8R9hEKCqaX+ri1yyuXr4BKp+V+o8lzKpWE+9+ lgLwgvJwJUvhCiIkmFRRW3F/SZij2uXFuLQqgHWTXGD5G0t56CwygOZbhWlNzPwsufnx FTh6xmAOy0pxx/lc5T9x53+2du6D7OzPfuBZIBDBcwc451WZkDp6eG/QdLmYZ153YO+P m49ogyEt7j8pFYZVqcA6dzZAyKfIk/wRc7J6UDqJn5ZtgA1zB7CrogSTxHfDnAoGj6r8 NTNlrGRvh4wgyJIuBjEJ5x8HP8ypMSfz/PNC/CnCVhH2IQqN4Dzr4MxLzhM+1ROVbi5h zofw== X-Gm-Message-State: AOAM531W5EJ/EiyVVcvubxh8ynCMc85XwSQDZNQVwtaBLDlNRQz3zT/P KreFlOPQlHnYylq67TVIU8fYpA== X-Google-Smtp-Source: ABdhPJylx3LpezRDuX8w89UdTXHs/SLHNSzIWCUZil5tHyPEMBpVUq27GCMZoqaYbSZnU91bKKv0aw== X-Received: by 2002:a05:6a00:2b4:b029:1f6:6f37:ef92 with SMTP id q20-20020a056a0002b4b02901f66f37ef92mr930875pfs.56.1615923814156; Tue, 16 Mar 2021 12:43:34 -0700 (PDT) Received: from relinquished.tfbnw.net ([2620:10d:c090:400::5:532]) by smtp.gmail.com with ESMTPSA id gm10sm217264pjb.4.2021.03.16.12.43.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Mar 2021 12:43:33 -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 v8 02/10] fs: add O_ALLOW_ENCODED open flag Date: Tue, 16 Mar 2021 12:42:58 -0700 Message-Id: <09988d880282a6ef0dd04d1fce7db1dbbd2d335c.1615922644.git.osandov@fb.com> X-Mailer: git-send-email 2.30.2 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 --- 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)