From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f6.google.com (mail-pj2-f6.google.com [74.125.227.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 88A4B39E6FD for ; Fri, 25 Sep 2026 19:02:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.134 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790362949; cv=none; b=D/tpMpGxVKUn/wg1J5qQM33OMw0TpmZ2/Cf1cH4CMj0tRNDylsAKbDTcn6Ac585w2w98XfYZtvgVffq/sLg9CxHEFbLbDvHEXA8NbqqrVemLDB1hkY92CSMBE+qCXh/z622nUe4yt+2a6KzXnbvgiSigv7QV6RYvJrKEbFchZAM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790362949; c=relaxed/simple; bh=miYvRcEGFmsRj3R3StAtd5ze/ExutceELLrIDIigKYo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ppXtjEaKcp5YqPSzT6HDstP990218bnvnzmj/9nEECb4XVV/nF05NiBiiGVHizIrrrTX++59oT+/xWViSJ5UHJWBr+4GPVxQHmKccBCJgw6MbtvFlvIeJd5cqAkw18qQUOOGMnoqtT0A+0YvWdLwrC1eO9agxrcgasiav3ub5Jg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=N4Z0c5iH; arc=none smtp.client-ip=74.125.227.134 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="N4Z0c5iH" Received: by mail-pj2-f6.google.com with SMTP id 98e67ed59e1d1-3964e7720afso747607a91.1 for ; Fri, 25 Sep 2026 12:02:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790362948; x=1790967748; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=ZbHzbG6KX4HjmnobdQp+43LfGiR+GIwDBr6SWkkO9VU=; b=N4Z0c5iHeZIAOdlqnWJXQD9W9KmfOn82z65vrzTrFjRMYKFNe2K+RB7I1B2bRudVim 8J6V49/+ciBaFeJIQUBEP34DY8m7hTw/2tGjHH69ZtZB5CVEcBRh316lyqs4BCOv1u/7 QP0qFDo/+Vlz1nJQe5NrIrOMKMCZL4SWCXcSR3tbvbo8H21RD7A0X5TPUVm+VvIOe31w emjqMwaRZFugSNIPyez1xgN3otfi9u7ZvdnOQ31Wl3gS0wPKtWFBzmJg3jIy+javRALB wj6STZ0SJTZa3Pjpgcj40D7W0/NrWe5mrr4Yq3erZtERx8Z6oGVFIUy+cVwtM6dnyc9c 36Yw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790362948; x=1790967748; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ZbHzbG6KX4HjmnobdQp+43LfGiR+GIwDBr6SWkkO9VU=; b=26dktcfS0mCO7Y83FtkpbnURyH0K+o1GFWufmBYWjyNpUv5iRutTOQzceZWcvvdTat 2JTIGrZkpfygMT/Vf7xSZM5DIDAJXb5wP5xEPo/FcKStOMVOHZ98jIMiuv0rRR5KHkOm 5dFY7cGJr5Q3ZOnjn79T2BsH0Y9CcFPwdlFFEaUK5nKEogCT/PlsNqd5/zGPrMjp0TWi tj0s9AEKUlIkqsO5ZWyH2/u/tHRQfWLdHiZraduCzpiNWw2QVZ/tucJdwysaz04TjhYA zdC6YmSIr3g4GeERNzOk0DNZJ32ahRI+aMyIcuUoQKNS3R5+RdoK6IJHjgrREUq8eV1n Q9mw== X-Forwarded-Encrypted: i=1; AKwUvBzQeyhYjVA2JJu0Neu4yp10P+aZwIgJP7sNEojgL6c5XduVU6SYdGHIBCGiX/hOIJiomRA=@vger.kernel.org X-Gm-Message-State: AFuF++njvlENXrTX+BIvi513VJ22CJG7LkZpu5coAg3hyOIaxSGrKzgE CtsjWHuYLF7bn91h721VxOK53lox14hkhu3r0W0N77cf4BmLQnbFxSfl X-Gm-Gg: AYBFou2rE9G5mKp2oHkxk5t/aVpgfCMo5EuVxpF4loZV1h1au96MgHTx/k/J4Cdx/sF FUbrUdIHrGyaHqpHHPmBECnauK8BLTcFXlMsA2RPWOxzpatHpTy+Oi/NrH8vYkA1fRydLYUvgMQ 85ILzEt+fOr4+lZkgmHFrrRoTsW/yPIVdUEbpd896vOWfTAoT5MtnwQrhtK1zQpkXtu5wbGdLmo wy+1tN/RjyCX1jzhlU50m2keOZP1ElItY2Cm+2MQmJ23jM2XKVimUKidP7R6+aDu4XAAvZxsCkf I+kEB9uuKKBQDEL0iWpX0AbyDHc6nyd9RGKynKPGOgf6FSQB/4AwENZRL2jdIg0IM2ORo/o0TLx Mk//U8olT2USIsPu0Y+RNNY5UQl6NJ2z6KCi/l2S4hgWRCFlaAMuiq4VIOceQxSlsOXn5rX9Jpx fejm+ZEauw3HJNC4EHEndjYMpW2RZvsvkfsBVn9GdpR2MxuwE46j48GHcJi8N/Q9hq X-Received: by 2002:a17:90b:1dcd:b0:39e:d36c:ee54 with SMTP id 98e67ed59e1d1-3a0bb55308cmr2493435a91.5.1790362947509; Fri, 25 Sep 2026 12:02:27 -0700 (PDT) Received: from localhost ([2a03:2880:2ff:5e::]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0976c8f8dsm12331068a91.12.2026.09.25.12.02.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Sep 2026 12:02:26 -0700 (PDT) Date: Fri, 25 Sep 2026 12:02:22 -0700 From: Stanislav Fomichev To: Breno Leitao Cc: David Ahern , Ido Schimmel , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , John Fastabend , Stanislav Fomichev , Shuah Khan , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, david.laight.linux@gmail.com, kernel-team@meta.com Subject: Re: [PATCH net-next 1/6] ipv6: reject a negative optlen in do_ipv6_getsockopt() Message-ID: References: <20260925-sockopt_expand_out_v2-v1-0-c3ef2e3bb5c0@debian.org> <20260925-sockopt_expand_out_v2-v1-1-c3ef2e3bb5c0@debian.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260925-sockopt_expand_out_v2-v1-1-c3ef2e3bb5c0@debian.org> On 09/25, Breno Leitao wrote: > IPv4's do_ip_getsockopt() rejects a negative optlen right after reading > it. do_ipv6_getsockopt() never has, and nothing downstream treats it as > an error either: len is an int, but every consumer compares it unsigned, > so -1 behaves as a huge value and each site clamps to its own reply > size. > > len = min_t(unsigned int, sizeof(int), len); > > So getsockopt(fd, SOL_IPV6, IPV6_TCLASS, buf, &len) with len set to -1 > answers 4 bytes and reports 4, rather than failing. > > This is a bug ready to bite us in the near future, let's get this fixed. > > I've found this because testing the rest of the patch was returning > inconsistency when optlen = -1. If I can do getsockopt with len=-1 today and get 4 bytes back, isn't that a uapi and we are gonna break someone?