From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA7FCC433F5 for ; Thu, 14 Oct 2021 15:02:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A157C6101E for ; Thu, 14 Oct 2021 15:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232985AbhJNPEY (ORCPT ); Thu, 14 Oct 2021 11:04:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:44032 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232773AbhJNPDE (ORCPT ); Thu, 14 Oct 2021 11:03:04 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 17EA861214; Thu, 14 Oct 2021 14:59:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1634223589; bh=QTt2i59o3hcholZQ93IdhnhqzxjeUOjWxaOVPdwi3Rs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dEhAuq06PSufTGLGoxo9yAVXz32FsOILIaRhaWocorq/PJEy2sHVIKDJlpcDxUpun y8dYeDZRSYcPovmgKNrtqi6G4HtgI9G6zXli3bbwJDKqv8j4HXdhWCFpfcCNQ9rrpp u9OJbMNKiZ1Wi2exTsj+0mGXzmhG4sI4CHJeA3Go= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann , Hans de Goede , Linus Torvalds , Sasha Levin Subject: [PATCH 5.10 15/22] vboxfs: fix broken legacy mount signature checking Date: Thu, 14 Oct 2021 16:54:21 +0200 Message-Id: <20211014145208.479447819@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211014145207.979449962@linuxfoundation.org> References: <20211014145207.979449962@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Linus Torvalds [ Upstream commit 9b3b353ef330e20bc2d99bf3165cc044cff26a09 ] Commit 9d682ea6bcc7 ("vboxsf: Fix the check for the old binary mount-arguments struct") was meant to fix a build error due to sign mismatch in 'char' and the use of character constants, but it just moved the error elsewhere, in that on some architectures characters and signed and on others they are unsigned, and that's just how the C standard works. The proper fix is a simple "don't do that then". The code was just being silly and odd, and it should never have cared about signed vs unsigned characters in the first place, since what it is testing is not four "characters", but four bytes. And the way to compare four bytes is by using "memcmp()". Which compilers will know to just turn into a single 32-bit compare with a constant, as long as you don't have crazy debug options enabled. Link: https://lore.kernel.org/lkml/20210927094123.576521-1-arnd@kernel.org/ Cc: Arnd Bergmann Cc: Hans de Goede Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/vboxsf/super.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/fs/vboxsf/super.c b/fs/vboxsf/super.c index d7816c01a4f6..c578e772cbd5 100644 --- a/fs/vboxsf/super.c +++ b/fs/vboxsf/super.c @@ -21,10 +21,7 @@ #define VBOXSF_SUPER_MAGIC 0x786f4256 /* 'VBox' little endian */ -#define VBSF_MOUNT_SIGNATURE_BYTE_0 ('\000') -#define VBSF_MOUNT_SIGNATURE_BYTE_1 ('\377') -#define VBSF_MOUNT_SIGNATURE_BYTE_2 ('\376') -#define VBSF_MOUNT_SIGNATURE_BYTE_3 ('\375') +static const unsigned char VBSF_MOUNT_SIGNATURE[4] = "\000\377\376\375"; static int follow_symlinks; module_param(follow_symlinks, int, 0444); @@ -386,12 +383,7 @@ fail_nomem: static int vboxsf_parse_monolithic(struct fs_context *fc, void *data) { - unsigned char *options = data; - - if (options && options[0] == VBSF_MOUNT_SIGNATURE_BYTE_0 && - options[1] == VBSF_MOUNT_SIGNATURE_BYTE_1 && - options[2] == VBSF_MOUNT_SIGNATURE_BYTE_2 && - options[3] == VBSF_MOUNT_SIGNATURE_BYTE_3) { + if (data && !memcmp(data, VBSF_MOUNT_SIGNATURE, 4)) { vbg_err("vboxsf: Old binary mount data not supported, remove obsolete mount.vboxsf and/or update your VBoxService.\n"); return -EINVAL; } -- 2.33.0