From nobody Wed Nov 5 18:32:09 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1536667482287895.38613097428; Tue, 11 Sep 2018 05:04:42 -0700 (PDT) Received: from localhost ([::1]:57355 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fzhPH-0006Qy-B3 for importer@patchew.org; Tue, 11 Sep 2018 08:04:35 -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 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) X-Virus-Scanned: by amavisd-new at test-mx.suse.de 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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_lon= g arg1, ret =3D 0; /* avoid warning */ break; case TARGET_NR_read: - if (arg3 =3D=3D 0) - ret =3D 0; - else { - if (!(p =3D lock_user(VERIFY_WRITE, arg2, arg3, 0))) - goto efault; - ret =3D get_errno(safe_read(arg1, p, arg3)); - if (ret >=3D 0 && - fd_trans_host_to_target_data(arg1)) { - ret =3D fd_trans_host_to_target_data(arg1)(p, ret); - } - unlock_user(p, arg2, ret); + if (!(p =3D lock_user(VERIFY_WRITE, arg2, arg3, 0))) + goto efault; + ret =3D get_errno(safe_read(arg1, p, arg3)); + if (ret >=3D 0 && + fd_trans_host_to_target_data(arg1)) { + ret =3D fd_trans_host_to_target_data(arg1)(p, ret); } + unlock_user(p, arg2, ret); break; case TARGET_NR_write: if (!(p =3D lock_user(VERIFY_READ, arg2, arg3, 1))) --=20 2.18.0 --=20 Andreas Schwab, SUSE Labs, schwab@suse.de GPG Key fingerprint =3D 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something completely different."