From patchwork Fri May 29 07:20:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Linus Walleij X-Patchwork-Id: 11577851 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 264CD1392 for ; Fri, 29 May 2020 07:22:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B0BC207F9 for ; Fri, 29 May 2020 07:22:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="hswH03OE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725854AbgE2HW1 (ORCPT ); Fri, 29 May 2020 03:22:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58740 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725808AbgE2HW0 (ORCPT ); Fri, 29 May 2020 03:22:26 -0400 Received: from mail-lj1-x243.google.com (mail-lj1-x243.google.com [IPv6:2a00:1450:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C77BC08C5C8 for ; Fri, 29 May 2020 00:22:25 -0700 (PDT) Received: by mail-lj1-x243.google.com with SMTP id c11so1360169ljn.2 for ; Fri, 29 May 2020 00:22:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=dl25yjAmJuE5AxkRwc5qz4dWHRUh+gkJVzHXFvs+rfg=; b=hswH03OEBTEgok3PtkSVa8NSZO20xTjVRoaF6RX18g3v51a3hFRNQq1utdUpGr9Z+q X0d8OiqCQkSgY7tBpDOoibOwLHpXeCKtZIfzhxr6OXnsSFPaccLBqztx6eRQDL6nQA96 R7Gh7KWcHd0rcO+5eyuklKCsu2JYny3gaHcv7QnG5kdWnIe1mi12m0EC/ShEZa9D/27y Wt8TPxDCkKvjnK61EJeBc1ygn05qOqGBeSquohq7VPUR0fRff9mPKPVyr5aK7UVkIGkj xH5lh580rUwSSMLJCkZZM8WZLHeb5HXjjF5A/8ck/w7RyZP/fxxukcleq03s9CqprG8h JUzQ== 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:mime-version :content-transfer-encoding; bh=dl25yjAmJuE5AxkRwc5qz4dWHRUh+gkJVzHXFvs+rfg=; b=gXSThJ90s4r0nweIU9lCtysytGEj774EjtslSKriQnG0BstG65NnHTydWsBiX27nCE R2BFVaJR29btmETN8dzUQ/TrXdva6v/p1MTOs8z+napUoWdMNE8ci8Q7q7tvLyp1bMYK CKSiq7kHnfeyXsYqCODnxyh6+Ut4lBXBZhb3muEx2sLQ+/SjVCXP3KqJw8o5CJ/XSbhg sVTH7lnM3YCeDZXj/rLRhtcKw+LA69McLu5BSnFEycClsyctTJqyu6q4FM0srr/cbDBz VRrsQom95ONEWRf3xkbg2R6OgMdt/5kynPB/jbLs+sGvdHdilhEfh/7uid1srm7B9jQg 3Dkg== X-Gm-Message-State: AOAM531gBVuaLYu5FWu3Qiaqu8UHo9qnMEY5MUf2cDUaNc1qTpui0n/7 qo9tb19WBO0qpuo87FBcEoANfQ== X-Google-Smtp-Source: ABdhPJw41qmTFNR1CsfUZRyTyoeD0cdsQ+X861XvpuY9BXFNpuN+0C0bxdkiKXtLjIsMiCEHv54kPQ== X-Received: by 2002:a2e:870b:: with SMTP id m11mr3122624lji.315.1590736943242; Fri, 29 May 2020 00:22:23 -0700 (PDT) Received: from localhost.localdomain ([92.34.219.140]) by smtp.gmail.com with ESMTPSA id k27sm2068399lfe.88.2020.05.29.00.22.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 May 2020 00:22:22 -0700 (PDT) From: Linus Walleij To: Theodore Ts'o , Andreas Dilger Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, qemu-devel@nongnu.org, Linus Walleij , Florian Weimer , Peter Maydell , Andy Lutomirski Subject: [PATCH v2] fcntl: Add 32bit filesystem mode Date: Fri, 29 May 2020 09:20:17 +0200 Message-Id: <20200529072017.2906-1-linus.walleij@linaro.org> X-Mailer: git-send-email 2.25.4 MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org It was brought to my attention that this bug from 2018 was still unresolved: 32 bit emulators like QEMU were given 64 bit hashes when running 32 bit emulation on 64 bit systems. This adds a flag to the fcntl() F_GETFD and F_SETFD operations to set the underlying filesystem into 32bit mode even if the file handle was opened using 64bit mode without the compat syscalls. Programs that need the 32 bit file system behavior need to issue a fcntl() system call such as in this example: #define FD_32BIT_MODE 2 int main(int argc, char** argv) { DIR* dir; int err; int fd; dir = opendir("/boot"); fd = dirfd(dir); err = fcntl(fd, F_SETFD, FD_32BIT_MODE); if (err) { printf("fcntl() failed! err=%d\n", err); return 1; } printf("dir=%p\n", dir); printf("readdir(dir)=%p\n", readdir(dir)); printf("errno=%d: %s\n", errno, strerror(errno)); return 0; } This can be pretty hard to test since C libraries and linux userspace security extensions aggressively filter the parameters that are passed down and allowed to commit into actual system calls. Cc: Florian Weimer Cc: Peter Maydell Cc: Andy Lutomirski Suggested-by: Theodore Ts'o Link: https://bugs.launchpad.net/qemu/+bug/1805913 Link: https://lore.kernel.org/lkml/87bm56vqg4.fsf@mid.deneb.enyo.de/ Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=205957 Signed-off-by: Linus Walleij --- ChangeLog v1->v2: - Use a new flag FD_32BIT_MODE to F_GETFD and F_SETFD instead of a new fcntl operation, there is already a fcntl operation to set random flags. - Sorry for taking forever to respin this patch :( --- fs/fcntl.c | 5 +++++ include/uapi/asm-generic/fcntl.h | 8 ++++++++ 2 files changed, 13 insertions(+) diff --git a/fs/fcntl.c b/fs/fcntl.c index 2e4c0fa2074b..10a6b712d3a7 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -335,10 +335,15 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, break; case F_GETFD: err = get_close_on_exec(fd) ? FD_CLOEXEC : 0; + /* Report 32bit file system mode */ + if (filp->f_mode & FMODE_32BITHASH) + err |= FD_32BIT_MODE; break; case F_SETFD: err = 0; set_close_on_exec(fd, arg & FD_CLOEXEC); + if (arg & FD_32BIT_MODE) + filp->f_mode |= FMODE_32BITHASH; break; case F_GETFL: err = filp->f_flags; diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index 9dc0bf0c5a6e..edd3573cb7ef 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -160,6 +160,14 @@ struct f_owner_ex { /* for F_[GET|SET]FL */ #define FD_CLOEXEC 1 /* actually anything with low bit set goes */ +/* + * This instructs the kernel to provide 32bit semantics (such as hashes) from + * the file system layer, when running a userland that depend on 32bit + * semantics on a kernel that supports 64bit userland, but does not use the + * compat ioctl() for e.g. open(), so that the kernel would otherwise assume + * that the userland process is capable of dealing with 64bit semantics. + */ +#define FD_32BIT_MODE 2 /* for posix fcntl() and lockf() */ #ifndef F_RDLCK