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 X-Spam-Level: X-Spam-Status: No, score=-8.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A03C1C55185 for ; Sat, 25 Apr 2020 09:31:05 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A7D3320700 for ; Sat, 25 Apr 2020 09:31:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=gmx.net header.i=@gmx.net 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4.90_1) (envelope-from ) id 1jSH2e-0002Ju-Er for qemu-devel@nongnu.org; Sat, 25 Apr 2020 05:24:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1587806645; bh=xytjJRSjIfdjxNKXlPzGzgoyxTH05XpuKItKJeKQuJs=; h=X-UI-Sender-Class:Subject:To:References:From:Date:In-Reply-To; b=NRxxAfxxsibNgXBJtoAWS7dUHVHt1sM7itVng2E3gGR8suXDLwzRsiUIZ7acOLmRb pLVQXE7Xm0JmVIyhupPj25ayUzvxhzHFTRYWmDzlicf6vDoPPxznpVGEcuNya9amED gW/X+qNUYm+kp+HmqtIFdXdt434izJatAJ+GgtLE= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [192.168.20.60] ([92.116.179.136]) by mail.gmx.com (mrgmx005 [212.227.17.190]) with ESMTPSA (Nemesis) id 1M8QWA-1jWgsu47Gq-004WsG; Sat, 25 Apr 2020 11:24:05 +0200 Subject: Re: [PATCH] linux-user: Drop unnecessary check in signalfd4 syscall To: Laurent Vivier , Riku Voipio , qemu-devel@nongnu.org References: <20200424210422.GB26282@ls3530.fritz.box> From: Helge Deller Autocrypt: addr=deller@gmx.de; keydata= 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fcrmRKjlaMO/pZh79cu+g6sjhOEAs8gUNmoOz1/ZtPkI+2+nGfFhNQ2Jj8Vcj8nAhqCZaoRXi YqPgvLxGAgeWm1GhMIXpsRDgd84x8wLghxq/B2Ma0KLLcntdtm65LLBeSDF0viKgZGZBV/M8t wJd1NK7wMnF4r6yT+9mJm1+x2Wq+3F5pfNqye4bXsvZHFmJszH8RywU3JgebmscHDAkSYmRpH CuA03UsIZWe5FDntz Received-SPF: pass client-ip=212.227.15.18; envelope-from=deller@gmx.de; helo=mout.gmx.net X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/25 05:24:06 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 212.227.15.18 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 25.04.20 10:39, Laurent Vivier wrote: > Le 24/04/2020 =C3=A0 23:04, Helge Deller a =C3=A9crit=C2=A0: >> The signalfd4() syscall takes optional O_NONBLOCK and O_CLOEXEC fcntl >> flags. If the user gave any other invalid flags, the host syscall will >> return correct error codes, so simply drop the extra check here. >> >> Signed-off-by: Helge Deller >> >> diff --git a/linux-user/syscall.c b/linux-user/syscall.c >> index 05f03919ff..ebf0d38321 100644 >> --- a/linux-user/syscall.c >> +++ b/linux-user/syscall.c >> @@ -7176,9 +7176,6 @@ static abi_long do_signalfd4(int fd, abi_long mas= k, int flags) >> sigset_t host_mask; >> abi_long ret; >> >> - if (flags & ~(TARGET_O_NONBLOCK | TARGET_O_CLOEXEC)) { >> - return -TARGET_EINVAL; >> - } >> if (!lock_user_struct(VERIFY_READ, target_mask, mask, 1)) { >> return -TARGET_EFAULT; >> } >> > > Perhaps we want to trigger the TARGET_EINVAL before the TARGET_EFAULT if > we have both cases? > > But I've checked the kernel, and the kernel does a copy_from_user() > before checking the flags, but it returns EINVAL rather than EFAULT. That's not the full picture, since the kernel is not consistent here! In the compat-case (32bit userspace on 64bit kernel) it returns correctly EINVAL and EFAULT: if (sigsetsize !=3D sizeof(compat_sigset_t)) return -EINVAL; if (get_compat_sigset(&mask, user_mask)) return -EFAULT; while in the non-compat case it returns EINVAL only: if (sizemask !=3D sizeof(sigset_t) || copy_from_user(&mask, user_mask, sizeof(mask))) return -EINVAL; I think the kernel should be fixed here... > We can remove the flags checking but we should also change TARGET_EFAULT > by TARGET_EINVAL. According to the different behaviour of the kernel mentioned above you won't get it correct either way. Helge