From patchwork Mon Oct 12 22:06:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Linus Walleij X-Patchwork-Id: 1381222 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256 header.s=google header.b=TJLs0p8e; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4C9CVt6KS9z9sS8 for ; Tue, 13 Oct 2020 09:08:38 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387726AbgJLWIi (ORCPT ); Mon, 12 Oct 2020 18:08:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732231AbgJLWIh (ORCPT ); Mon, 12 Oct 2020 18:08:37 -0400 Received: from mail-lf1-x144.google.com (mail-lf1-x144.google.com [IPv6:2a00:1450:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42851C0613D1 for ; Mon, 12 Oct 2020 15:08:37 -0700 (PDT) Received: by mail-lf1-x144.google.com with SMTP id l2so19917879lfk.0 for ; Mon, 12 Oct 2020 15:08:37 -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=Er9outiRWHyk/leMtSr3CNlG0IeLWwXg/xMOKQHeA64=; b=TJLs0p8ef4M8/2cD6lB9hj/ouQXXIQ/K0meIiWe4zNhqW2s0ngXyIXQSYlacBFeFlj kAIAmHPxQb1/ujaGBZFb+dfwSePuqxvopJiXkpGgjipwT732nRx+BxQq5xTHYgdGIOAs isyVPJDcayUq1+Kq2+ze6a/bcqxsM1zaKE47QWncvbSgkZIu/P+xBkVlu92rPPdxxhCJ uf6IILkn1+fZNd5nT3ek4QfnUSzfvR1vnFUHYKQRBnDdsyUfUshec2t1/Eul5nz6vq2e iiMoUngpjYSAUATlZWlh89jleNr2DKD+euTyWeVfSZAdLsydM7LuN5j4+86z26nK9/j5 rqWw== 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=Er9outiRWHyk/leMtSr3CNlG0IeLWwXg/xMOKQHeA64=; b=mdxLs5TnCL4XwucrLwy5PLVQAmMDfIYKPF0+HDpO8+GwQX7i4v/EzcFppiNKVDxlsH e7pZBmeQF1aal7r1QZQ3hR+kp1i1Ki2rrI/EK6amZP7W6eYj/OsPp3Bug/803wQ1yLN8 gxFF01zK7GpeNtyR8tAknIwykL9y5r9WMskq+b91c/Hy3DSrm7YrTLXNtmXRCHRbhzhN WQnUimY9sIvtWOBH56gEqd1uMP83vbxCsmTEsoLx0zWSo3FpVPO8sAaXsQLQiAkJx6gS tekISVqfdUwvF7UsmmPg3nXuJ0k+yJYCsV+pAqjgUTJoZq44b0/seWd6HTPu1mn3T9mq ihWw== X-Gm-Message-State: AOAM5318DR51uMCgB7tnKWetNb0TV94nongTnVZL1IrBpv3w5efCsNXc IFsJmVEa8jDx0+K6uhEJChCSGA== X-Google-Smtp-Source: ABdhPJxmiM6IlJtuyaoQ8VZOOBemBYKqhzqgDG6ZrEeg+bRyV1gNNd+WNqR3yadfn3+/FcWbnCxyLA== X-Received: by 2002:a19:824f:: with SMTP id e76mr6874758lfd.572.1602540515605; Mon, 12 Oct 2020 15:08:35 -0700 (PDT) Received: from localhost.localdomain (c-92d7225c.014-348-6c756e10.bbcust.telenor.se. [92.34.215.146]) by smtp.gmail.com with ESMTPSA id a201sm3039261lfd.213.2020.10.12.15.08.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Oct 2020 15:08:34 -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 v3 RESEND] fcntl: Add 32bit filesystem mode Date: Tue, 13 Oct 2020 00:06:20 +0200 Message-Id: <20201012220620.124408-1-linus.walleij@linaro.org> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@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 v3->v3 RESEND 1: - Resending during the v5.10 merge window to get attention. ChangeLog v2->v3: - Realized that I also have to clear the flag correspondingly if someone ask for !FD_32BIT_MODE after setting it the first time. 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 | 7 +++++++ include/uapi/asm-generic/fcntl.h | 8 ++++++++ 2 files changed, 15 insertions(+) diff --git a/fs/fcntl.c b/fs/fcntl.c index 19ac5baad50f..6c32edc4099a 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -335,10 +335,17 @@ 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; + else + 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