From patchwork Tue Sep 11 12:03:04 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Schwab X-Patchwork-Id: 968529 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=suse.de Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 428k8m47GHz9s3Z for ; Tue, 11 Sep 2018 22:03:51 +1000 (AEST) Received: from localhost ([::1]:57349 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fzhOU-0005AC-EG for incoming@patchwork.ozlabs.org; Tue, 11 Sep 2018 08:03:46 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44943) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fzhNv-000585-Mj for qemu-devel@nongnu.org; Tue, 11 Sep 2018 08:03:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fzhNp-00061S-Ut for qemu-devel@nongnu.org; Tue, 11 Sep 2018 08:03:11 -0400 Received: from mx2.suse.de ([195.135.220.15]:54158 helo=mx1.suse.de) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fzhNp-000601-OF for qemu-devel@nongnu.org; Tue, 11 Sep 2018 08:03:05 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id AE247AF7C for ; Tue, 11 Sep 2018 12:03:04 +0000 (UTC) From: Andreas Schwab To: qemu-devel@nongnu.org X-Yow: I smell like a wet reducing clinic on Columbus Day! Date: Tue, 11 Sep 2018 14:03:04 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x (no timestamps) [generic] X-Received-From: 195.135.220.15 Subject: [Qemu-devel] [PATCH] linux-user: don't short-circuit read with zero length X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" A zero-length read still needs to do the usual checks, thus it may return errors like EBADF. Signed-off-by: Andreas Schwab --- linux-user/syscall.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 643b8833de..202d3c287d 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -7930,18 +7930,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, ret = 0; /* avoid warning */ break; case TARGET_NR_read: - if (arg3 == 0) - ret = 0; - else { - if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0))) - goto efault; - ret = get_errno(safe_read(arg1, p, arg3)); - if (ret >= 0 && - fd_trans_host_to_target_data(arg1)) { - ret = fd_trans_host_to_target_data(arg1)(p, ret); - } - unlock_user(p, arg2, ret); + if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0))) + goto efault; + ret = get_errno(safe_read(arg1, p, arg3)); + if (ret >= 0 && + fd_trans_host_to_target_data(arg1)) { + ret = fd_trans_host_to_target_data(arg1)(p, ret); } + unlock_user(p, arg2, ret); break; case TARGET_NR_write: if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))