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 AEE30C54FCB for ; Sat, 25 Apr 2020 21:55:10 +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 6CB6C20714 for ; Sat, 25 Apr 2020 21:55:10 +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 1jSSfJ-0001s4-2L for qemu-devel@nongnu.org; Sat, 25 Apr 2020 17:48:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1587851318; bh=xPRzfUY6UR0+nipgQZDLUXMKknzrpMvhKXjVLROYD5Y=; h=X-UI-Sender-Class:Subject:To:References:From:Date:In-Reply-To; b=QHcy4ChbZg2lJnox0vK69AL3F1Eh5sTrn2Hw0C9wxI0PG0V6jSWnCia/+VOx/1gMj WYb4XIeQxeoPMVkh5WURhxjo6LlUfUQX0EVcc57zZp60FF9ZQKoa1cqPMreAOgB+So RhimWlpE2cl+4UH5ymGiF51dVRcvuHTuKXBOWDbY= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [192.168.20.60] ([92.116.179.136]) by mail.gmx.com (mrgmx104 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MEm6F-1jR2wX2jRD-00GFlo; Sat, 25 Apr 2020 23:48:38 +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> <2703086a-d283-e780-a427-ce84ed31f852@gmx.de> <67496bb6-1734-ff27-c734-aa01a7a670a4@vivier.eu> From: Helge Deller Autocrypt: addr=deller@gmx.de; keydata= mQINBF3Ia3MBEAD3nmWzMgQByYAWnb9cNqspnkb2GLVKzhoH2QD4eRpyDLA/3smlClbeKkWT HLnjgkbPFDmcmCz5V0Wv1mKYRClAHPCIBIJgyICqqUZo2qGmKstUx3pFAiztlXBANpRECgwJ r+8w6mkccOM9GhoPU0vMaD/UVJcJQzvrxVHO8EHS36aUkjKd6cOpdVbCt3qx8cEhCmaFEO6u CL+k5AZQoABbFQEBocZE1/lSYzaHkcHrjn4cQjc3CffXnUVYwlo8EYOtAHgMDC39s9a7S90L 69l6G73lYBD/Br5lnDPlG6dKfGFZZpQ1h8/x+Qz366Ojfq9MuuRJg7ZQpe6foiOtqwKym/zV dVvSdOOc5sHSpfwu5+BVAAyBd6hw4NddlAQUjHSRs3zJ9OfrEx2d3mIfXZ7+pMhZ7qX0Axlq Lq+B5cfLpzkPAgKn11tfXFxP+hcPHIts0bnDz4EEp+HraW+oRCH2m57Y9zhcJTOJaLw4YpTY GRUlF076vZ2Hz/xMEvIJddRGId7UXZgH9a32NDf+BUjWEZvFt1wFSW1r7zb7oGCwZMy2LI/G aHQv/N0NeFMd28z+deyxd0k1CGefHJuJcOJDVtcE1rGQ43aDhWSpXvXKDj42vFD2We6uIo9D 1VNre2+uAxFzqqf026H6cH8hin9Vnx7p3uq3Dka/Y/qmRFnKVQARAQABtBxIZWxnZSBEZWxs ZXIgPGRlbGxlckBnbXguZGU+iQJRBBMBCAA7AhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheA FiEERUSCKCzZENvvPSX4Pl89BKeiRgMFAl3J1zsCGQEACgkQPl89BKeiRgNK7xAAg6kJTPje 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qkHEXP5kPSmIscWt79XP+cko1y3xRZhl+w8zQXEmKhtNx1XVuQKL4rhKq6v8+WmzVcU9HYF7w TopImAtNZqOpImNmfelCS0jS4GNqSzpo+TNlDylDL8iIRp6u36DwSiCtgk0hm7MOTeucBx8Iq 49UyUqohHQcMrwDyHaY9lNMa4ZOdheX/JKxwdiP7B/u3gAmTrAWL8Eq3HadSEqtPUnhsfT3IF 0UokVH5HlPDbbLkkiDVV1nZpEUQ5kXQ+MJpz1IX3Bjl371saVj/iTisBjGfbpwIBl56BDGc6w evSk+gS1EquYlC/3OPIZ/Tr/7vqiB7tDlka3HlDuJ7yLPaX+8KEDOW6P2D1D2L6sCMFfn1N8g zhnsS0wEp7KVYB+lrd1KgQDHKcYRqLEWx0y/hWCSIjymJX+IloLaY29yt/+oJvmY+V02MWYGR t4rUg84FWiMybBD7jUv216vCCS4spswKx0Sh2FuggBjEdzK3lRyDEbHQYIeJ3j9QKPkAISwyY eFlfgkkbyxbKcO+igRuHMzdwGbnQZl/N4kOw8eZmXtWTqiMJvhgH+1gK3ayU/HsB5/x/uJf12 MVni8UQUNwnLTdZhpLJMtiHhWA/fIbdusp8o0lvalkBAIQuTwFZjdouAkxFJDlyTTd3J6e0xY iWHvCjYFX789HCWc1VGTK8bil75JB3BblHIjyR6h685/X05809pu/MPPd2J6NVqZKqyPlaCQa M7udWWttfkHTRbh6Jejj2QnyKFI1oB1ytL8XdgDosTEqTyI1G81chdNphN7TnhndD3sLBdZYq NFmOPVkYurJXXg+A/7ED85mFselgqCAcuKICymSgLesfvYvL2xRa97kqbB6UsLLPzcAvvVToC 1JH3IZ/vlgKoPa314sN4FTgFgDstuix5Hx2oPLIdCrobp6hTtkx/0g7TZwUBoOvxZ8nNOIuMQ rE/j994YR8S3w0mcotiIaVt2xDcAo2DB2vRMCHegnXjw5ObBmcjRvKmTW5b+1P+4afN3ldF/m Pog3vOnXcjBiFcXNqBCtqfG0SJ5b9/PTNqFtCBddCZY9fR6NuUgni2byt5EPBMCDZGiUCxhMf 1HnvXTDA8alKhZXPvcUwoxw3sUKmAvDrdvfFG7vltUjtgsO/WLcdgmqx0Smbgyj3vZlisWtRZ LTM7AVcP/0000HPxfGog6pzHnOTO/D4tikMmPXiOAydEYe7c5TLIe8iAPQc8R7tYlivtZHF4E 1HJxh9aCkOp7JKRZi Received-SPF: pass client-ip=212.227.17.21; envelope-from=deller@gmx.de; helo=mout.gmx.net X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/25 17:48:46 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 212.227.17.21 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 12:03, Laurent Vivier wrote: > Le 25/04/2020 =C3=A0 11:24, Helge Deller a =C3=A9crit=C2=A0: >> 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 wi= ll >>>> 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 m= ask, 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 correct= ly >> 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_EFAU= LT >>> by TARGET_EINVAL. >> >> According to the different behaviour of the kernel mentioned above >> you won't get it correct either way. > > If we refer to manpage, EFAULT is not one of possible errors. The manpage doesn't mention any error code for a bad mask address, and IMHO the manpage should reflect the real coding, not vice versa. I've just sent a RFC patch to the kernel mailing list. It's not a critical problem, but it would be nice to be at least consisten= t across the implementations. Either both should return always EINVAL, or both should return EFAULT. If it gets accepted I'll send a patch to correct the manpage accordingly afterwards, and then we can adjust qemu. Helge