From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.160.49 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792428713; b=A/KC/qDDtLcoiqvQVutreYaPei5nECNglXF2nnufQnIhNCBt5Z5A+gH4JVtkl2lpaSJt lmVOO9Sudg/kAABMQ+KMQ4SHwxclqYv2OisheeIcXisMwQqzKdtWoAb1sRngSXuXXXT7+ H49BwgMiStuzkhZkYy2ymATGU6D+GNYe0tW1ueg/plk+e8QWh463Wen6MTfOzl6rTLndf 3yubA+YZaFyCip010OqJX/kZVIwINsfl9A/NlgYidt/oDIrhICdnsZkNwuSipZlHCAx+S x7SlERrZ+IcKHMn2HW2USofZSphLHp6v3Xux2TAZho0l4kd4KnngktG8EnquMDDC+AQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792428713; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:Content-Transfer-Encoding: In-Reply-To; bh=GGZr1o3aGctzMnwygsbHm91Fqbk3LTUuMaHfiMRf6n8=; b=3LeHBxaA6Q5CgeJVtrUQCEphDyS5TAm/GBcv3CYXKIB8Tm4DN9FiTW1QIxtyVKdb8u/0 fHgjgthHPvAG7V6T6ayzI6HFWkCAiAVkVsItGYSmpyIZixmeM3CoE7CKpcq9mGTUveS4f q40+mE/hKGjOcJ2okMr22/1Ag0Eyzhfd20BULsS2mdTFN0auf3Z9OmxSM7P0pmxCstx9D LJJUVpNgmY9yAazW16FgEmiSq0HvDuaOeSXT/LXvd/wFMjQjR6SnW3Xmn58dc8J8EgtNy 78dF8M7AtDJvnyxoaj4bA0hFGZjvHKa7Mz5VvgexnDgiGHar71OgbIWYuR3SNn4dabQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=cloudflare.com; spf=pass smtp.mailfrom=cloudflare.com; dkim=pass header.d=cloudflare.com header.i=@cloudflare.com header.a=rsa-sha256 header.s=google09082023 header.b=CAOOROj6; arc=none smtp.remote-ip=209.85.160.49 Received: from mail-oa1-f49.google.com (mail-oa1-f49.google.com [209.85.160.49]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8767F606A31C for ; Mon, 19 Oct 2026 16:51:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 8767F606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cloudflare.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cloudflare.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=cloudflare.com header.i=@cloudflare.com header.a=rsa-sha256 header.s=google09082023 header.b=CAOOROj6 Received: by mail-oa1-f49.google.com with SMTP id 586e51a60fabf-4877837890fso1132871fac.2 for ; Mon, 19 Oct 2026 09:51:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google09082023; t=1792428711; x=1793033511; darn=lists.linux.dev; h=in-reply-to:content-transfer-encoding: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=GGZr1o3aGctzMnwygsbHm91Fqbk3LTUuMaHfiMRf6n8=; b=CAOOROj6KwPYxU1HNVqx01Rm+1GHe5qarE0nM+OxB4psSKfaeaiK3JxdaLqT91pq04 QDzM0kh3oWH4kjeGije6FoIGkqSbKzQajTl9ABUnsm8a2uRjXR2E3YVrp31mqsNYWDKn eHbbhhgfxcoC1oerbqc7AItpM2kcXKB2v4VuB7ChUqd15U8B3e1s0j7r6aHAJj2Yt74g t9V6xhRF9kngpKYZ/lvd+SOeqk8/SMGZQ+3F7OrnKlwueuqXvSuFs6HlmLjxYBNONovo 31f+0FedTlyrHTnZ2PayofSpdUvrUTB+V0Yi2ijWmVn+T2Y31dLn1bBrumTelJWI/L7s U0UQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792428711; x=1793033511; h=in-reply-to:content-transfer-encoding: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=GGZr1o3aGctzMnwygsbHm91Fqbk3LTUuMaHfiMRf6n8=; b=T46wv628FcjWDtMDUhPiFNOPWQPYhrgozml3SYUlJd0MCP9JKihY6Shb+FP8mX5bZ1 MH3Yl60SqdOAVU5sYlGPLvUlAohBKMliCJDltBZK/ZGVGiRP0wHstyf726HQLp1NHk7l uLdWOQwWv1AnaGMc63Q9qi+lpGLBecXaWh4rS/edVnc1iPs6upsHzd0ye4WUekntGZPB mUZkuyitEhQPnksxo/MUJ4Vz1Lh25penfLmmDkrVkvOn033ZUHoLo852HM91JPpW/g3Y 4d9g6oGgwO9/kkqG+csSC/LoiGIspIYp2GrJloRFuU9cgOzIIOK8AMkEuHkIxRpTmRxg KBCQ== X-Forwarded-Encrypted: i=1; AKwUvBzIgdjWtADFPcfLao4kbnqa04R6H9BBEcXSeJx4u2kjOlSlMK91kCkX0eoAOEANLmTPFG+TuJ/pDk1agIZSZw==@lists.linux.dev X-Gm-Message-State: AFq9FYIeOYBsRDnybsQgDRfn5GNbNMOGM6dFMlBbIxZoXkiBww25rNrJ Nqt5rsSTbtca92YRQzah83toiR9Tcct7qGhdaBgrpqpULRLtQQxFjy7ZI2VdVrn+jJE= X-Gm-Gg: AYBFou3gbItmWOyjauu7qrh4LQSpCUGd9hSyrHMJRi1dVmaRBBAQZapSUQUjtlkcVPZ UR/wKrbuiK39EESDIinArNm9zQizx3hK7NJM2z3VYFT3YPPkvI386Gx0yMUVbPo1nNbG/CBgVUQ nTnHcLxyusPnvK9OvjzfXvl58AC8PBtXQAn4qsgBMliUHzwgg5V4nArLUuH8noQ5a0L59KQLOK5 avgRD4scqYGtDe+qTdwo7jxF2o+wHzR1dE8k8dXFebJqOCgR1CmjaCFtNPIz96djSDUcMd5vBvT gRLcNONFzB2uM6vwnBxmE5US3136kMK+Sw/zfRn/TLElyfQ2qwVvQbKz0A4mibxjh/nEeKY8pCA VnNig5npB3gZxi7qQ9y5vPbEsp5/kzG0bV74ZPVjkWMXD+kkUIU3VP1BuzB9mnx3JFFWXlgttgA iOvhD25xaxotDHq82tDCoN0TIx1gt432eWnA5AKgxn1G4ALSY39MBDn9RyIBZ1ol8ygibVGa+5u 5BeKBUrATu2FhZAeZsirjgUZ5ASvXShi73x9Sk= X-Received: by 2002:a05:6870:3c13:b0:494:b8f4:9a22 with SMTP id 586e51a60fabf-4a757917efemr6305805fac.28.1792428710995; Mon, 19 Oct 2026 09:51:50 -0700 (PDT) Received: from 20HS2G4 ([2a09:bac6:bf21:1c64::2d4:c2]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4a73b640adesm8785424fac.10.2026.10.19.09.51.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Oct 2026 09:51:49 -0700 (PDT) Date: Mon, 19 Oct 2026 11:51:46 -0500 From: Chris Arges To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Willem de Bruijn , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Phil Sutter , Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Xuan Zhuo , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, virtualization@lists.linux.dev, Max Krasnyansky , Rusty Russell Subject: Re: [PATCH net v3 0/8] more virtio-net csum hardening Message-ID: References: X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 2026-10-19 08:03:00, Michael S. Tsirkin wrote: > > As reported first by Paulos Yibelo (after which > others, credited below, found more ways the bug can affect users): > > allowing untrusted hardware to specify csum start/offset for > CHECKSUM_PARTIAL was not a good idea, because, if it edits the packet > outside the actual checksum, and depending on the setup, the networking > stack could be looking at the packet both before and after the edit, and > seeing different results. > > Previously, commit 6785011f8b16 ("ipv4: validate checksum_start before > completing checksum") validated all known instances where this > causes the most grief, but the real fix is to make sure > that either only actual checksum fields are ever edited, > or the checksum is completed before the net stack looks at it, > so it is always consistent. > > > This basically goes back to > what we did before f43798c27684 ("tun: Allow GSO using virtio_net_hdr"), > except in a narrow list of specified known good cases. > > > Summary of the patchset: > > These are definitely net material (and seem to be too big for stable, > or I would recommend backporting there, too): > > net: account for ingress-resolved virtio net hdr state > - accounting, not the fix itself, dependency of the next one > net: resolve uncommon partial checksums at ingress > - fix itself > net: add a sysctl to opt out of virtio net hdr checksum validation > - reducing risk of the fix by adding a sysctl to disable it > > These are cleanups, can be deferred to net-next, too: > > net: add ip4_parse() > virtio_net: cleanup protocol calculation > - cleanup resulting code duplication > (kept separate to simplify backporting) > > Fixes: f43798c27684 ("tun: Allow GSO using virtio_net_hdr") > > Changes since v1: > - reorder patches to fix bisectability, addressing > a comment by Björn Töpel. > - code refactoring, different patch splitup, > a sysctl knob to disable as suggested by Willem de Bruijn. > - fix a bunch of minor issues spotted by LLMs > > > Changes since v2: > > virtio_net: parse tunnel csum_start little-endian > - new patch. correctly parsing the header is a dependency > of validating it, otherwise i do not know what to validate > > net: account for ingress-resolved virtio net hdr state > - make rx_csum_sw counter 64 bit so it won't wrap > (spotted by LLM review) > > net: resolve uncommon partial checksums at ingress > - tunnel fixes to bugs noticed by Willem de Bruijn and > Chris Arges > - restore the csum_offset checks as suggested by Willem > - parse csum_start in the tunnel header little-endian like > the rest of it (spotted by LLM review) > > net: add a sysctl to opt out of virtio net hdr checksum validation > - the knob is no longer writable by root inside a user > namespace: changing it now requires capable(CAP_NET_ADMIN) > suggested by Willem de Bruijn > > net: add ip4_parse() > - comment converted to kernel-doc format (Willem de Bruijn) > > um: vector: honor virtio net hdr conversion failures > - commit log tweaks > > New patch: > um: vector: trim skbs before verifying the header > found by code review > > Somewhat tested, tunnel also tested now, um part compiled only > I was able to run my tests and can confirm no more KASAN errors. I did not test the um patches. Tested-by: Chris Arges > > Michael S. Tsirkin (8): > net: account for ingress-resolved virtio net hdr state > um: vector: honor virtio net hdr conversion failures > um: vector: trim skbs before verifying the header > virtio_net: parse tunnel csum_start little-endian > net: resolve uncommon partial checksums at ingress > net: add a sysctl to opt out of virtio net hdr checksum validation > net: add ip4_parse() > virtio_net: cleanup protocol calculation > > Documentation/admin-guide/sysctl/net.rst | 19 ++ > arch/um/drivers/vector_kern.c | 6 +- > arch/um/drivers/vector_transports.c | 4 +- > drivers/net/tap.c | 4 +- > drivers/net/tun.c | 41 +++- > drivers/net/virtio_net.c | 2 +- > include/linux/ip.h | 27 +++ > include/linux/virtio_net.h | 272 ++++++++++++++++++++++- > include/net/netns/core.h | 1 + > net/bridge/br_netfilter_hooks.c | 15 +- > net/core/dev.c | 6 + > net/core/net_namespace.c | 1 + > net/core/sysctl_net_core.c | 60 +++++ > net/ipv4/ip_input.c | 13 +- > net/ipv4/netfilter/nf_reject_ipv4.c | 13 +- > net/packet/af_packet.c | 4 +- > 16 files changed, 445 insertions(+), 43 deletions(-) > > -- > MST >