From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm2-f9.google.com (mail-wm2-f9.google.com [74.125.225.137]) (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 ABF3B3DEAD6 for ; Mon, 10 Aug 2026 18:55:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.225.137 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786388132; cv=none; b=GspCDPxnVFY5OwgOcEKQBeJ3ZL2DoD6ciCrZYUTAoUrbCm/ZCXVfOa5OO8WdIdRmrRj9yPGSsq5DhNPJP3WCjYcee5Z6REKRj/ND+QGLgBPVbfLjXFrTiOn5RVyR43EuvPA9FqANQAoA10qdQnSvGU7PZGYUtQmTbyxTNsSnq2w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786388132; c=relaxed/simple; bh=e6eOL0FJC5ket9uPlrfy/upR4VpR9UnwvB9RfL7zehw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lcfcrazgG+FhXwFECyaOStHvHPfTLuQbY8DdbIIZS2ZROCT19azEZJL55s8uF6w3hY6s20hE5Z/qCnDa2tCNvRq6cn3uKrNRtjdHkkkT1a6a1CQw1bTta5W3km6HnQR0SVgfZUsbqD+AZKsMb/IvnjgzWQhoWKtwcoSunuwRinI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ovn.org; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=74.125.225.137 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ovn.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wm2-f9.google.com with SMTP id 5b1f17b1804b1-49556ce3549so8496475e9.0 for ; Mon, 10 Aug 2026 11:55:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786388129; x=1786992929; h=content-transfer-encoding:content-type:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=eDPDzOSNgjKp5sZX+BjdxXLjvfDLRA/UmcvVnE0yrDg=; b=USRtd4vaY307ZCrbjsXjh5flNSnmz4dh79Uk/zX3m2PgcJTjPkU5EsaiFQWSb1EVVJ 7yBL2k9CHiwwEmE2V+oJojPmMzT5rF0O1Kxbdt9x/uB7JVtQVpn0dx3NO723IyxWJ8YO fj58vt7YnTrTyhvKIqR/yvykCcnkPfMiB6eg1ozGWsuE6YsLolWPGQ4/7zKhoHNfSfG9 Tl6T9ElAZHwkf068SaL/xbwxFRM2Jsl14Vd5d7p1vO2CUmd1z/On3QasCCbTaczcNEEM 48Fs77GIU2JaErx+Yk8a26k0cBN0haA3u5gyj5v6q0TQ6kMO7cXZt1v8UV9n8KP0ZvAL 8JwQ== X-Forwarded-Encrypted: i=1; AHgh+RrN8xpsroh7W3xIOFIURTQY4ZCPEmzBGTVuvkp86PZGxF8fXYaA8TbkEe/2UsOBAnUHoqNP41I=@vger.kernel.org X-Gm-Message-State: AOJu0YxVyo53dyGhCi6jmcch0Tgzs4Gddc0LQYMa8GHgYUOLRBedIRIW 4Ej8Yr0lc1LJq1GjeXif7O6xcdsxwZ9qKBC5SpyhPjgphTI3AnOG4uEi X-Gm-Gg: AR+sD12+y64jkvBtIglKRqQi5zPxAwLkHlW3b9LUKm++gNyEO3cGYZs7BL7m+BN+9Nt j8WSatZ+MxYZqF6XIUck1xJ5bDv8y9KtQH6PI0lsMUzykb52Nm5niDWjkurQEvcRYpSQ8wZuf27 mPhYRxd9ETXetw2fGP3lopLkLBPgY+E0TxU7zm9RP9KA/mlXt1PZnhpeI93ybHTxO0RWV/NCL53 33o/PhEb59wdpqNQRTiE9X3SzQAqo8eiQnXa1pRW6bj2eb7BrE5s10ziH4w2dLRBhWgrZhZkBMr yLONEqyh/pm+EeZsCqWGarZ8gGjYpVRjZGdkqjfFAg1pZMSAgxtWTe+8YT/CjE03pCTpkZ9O6ue NcGEMdEuUDt9I+drFbjinOpKhmFUl7w0+2ySULHHVL9GiYnsGNRvi9hmYFFNumlJmtLEG9qIfB4 fZEEgDTRYHp/I3uZQPf2PBLT9crnRLyhbn/1BaXul8kAFTKpksygXlzy0ZviiIP+86P4ovXkVUT PHs02ISz4DIYWPJYQ== X-Received: by 2002:a05:600c:6d90:b0:495:4a22:d684 with SMTP id 5b1f17b1804b1-49959e2f00emr346681905e9.10.1786388128609; Mon, 10 Aug 2026 11:55:28 -0700 (PDT) Received: from [192.168.88.241] (89-24-57-65.nat.epc.tmcz.cz. [89.24.57.65]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-499740db139sm11106045e9.7.2026.08.10.11.55.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Aug 2026 11:55:28 -0700 (PDT) Message-ID: Date: Mon, 10 Aug 2026 20:55:26 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2 1/2] net: core: propagate unreadable flag in skb_zerocopy To: Mina Almasry , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dev@openvswitch.org Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Neal Cardwell , Kuniyuki Iwashima , Aaron Conole , Eelco Chaudron , Ilya Maximets , Jason Xing , Pavel Begunkov , Stanislav Fomichev , Bobby Eshleman , Florian Westphal References: <20260810180956.2348280-1-almasrymina@google.com> Content-Language: en-US From: Ilya Maximets Autocrypt: addr=i.maximets@ovn.org; keydata= xsFNBF77bOMBEADVZQ4iajIECGfH3hpQMQjhIQlyKX4hIB3OccKl5XvB/JqVPJWuZQRuqNQG /B70MP6km95KnWLZ4H1/5YOJK2l7VN7nO+tyF+I+srcKq8Ai6S3vyiP9zPCrZkYvhqChNOCF pNqdWBEmTvLZeVPmfdrjmzCLXVLi5De9HpIZQFg/Ztgj1AZENNQjYjtDdObMHuJQNJ6ubPIW cvOOn4WBr8NsP4a2OuHSTdVyAJwcDhu+WrS/Bj3KlQXIdPv3Zm5x9u/56NmCn1tSkLrEgi0i /nJNeH5QhPdYGtNzPixKgPmCKz54/LDxU61AmBvyRve+U80ukS+5vWk8zvnCGvL0ms7kx5sA tETpbKEV3d7CB3sQEym8B8gl0Ux9KzGp5lbhxxO995KWzZWWokVUcevGBKsAx4a/C0wTVOpP FbQsq6xEpTKBZwlCpxyJi3/PbZQJ95T8Uw6tlJkPmNx8CasiqNy2872gD1nN/WOP8m+cIQNu o6NOiz6VzNcowhEihE8Nkw9V+zfCxC8SzSBuYCiVX6FpgKzY/Tx+v2uO4f/8FoZj2trzXdLk BaIiyqnE0mtmTQE8jRa29qdh+s5DNArYAchJdeKuLQYnxy+9U1SMMzJoNUX5uRy6/3KrMoC/ 7zhn44x77gSoe7XVM6mr/mK+ViVB7v9JfqlZuiHDkJnS3yxKPwARAQABzSJJbHlhIE1heGlt ZXRzIDxpLm1heGltZXRzQG92bi5vcmc+wsGUBBMBCAA+AhsDBQsJCAcCBhUKCQgLAgQWAgMB Ah4BAheAFiEEh+ma1RKWrHCY821auffsd8gpv5YFAmfB9JAFCQyI7q0ACgkQuffsd8gpv5YQ og/8DXt1UOznvjdXRHVydbU6Ws+1iUrxlwnFH4WckoFgH4jAabt25yTa1Z4YX8Vz0mbRhTPX M/j1uORyObLem3of4YCd4ymh7nSu++KdKnNsZVHxMcoiic9ILPIaWYa8kTvyIDT2AEVfn9M+ vskM0yDbKa6TAHgr/0jCxbS+mvN0ZzDuR/LHTgy3e58097SWJohj0h3Dpu+XfuNiZCLCZ1/G AbBCPMw+r7baH/0evkX33RCBZwvh6tKu+rCatVGk72qRYNLCwF0YcGuNBsJiN9Aa/7ipkrA7 Xp7YvY3Y1OrKnQfdjp3mSXmknqPtwqnWzXvdfkWkZKShu0xSk+AjdFWCV3NOzQaH3CJ67NXm aPjJCIykoTOoQ7eEP6+m3WcgpRVkn9bGK9ng03MLSymTPmdINhC5pjOqBP7hLqYi89GN0MIT Ly2zD4m/8T8wPV9yo7GRk4kkwD0yN05PV2IzJECdOXSSStsf5JWObTwzhKyXJxQE+Kb67Wwa LYJgltFjpByF5GEO4Xe7iYTjwEoSSOfaR0kokUVM9pxIkZlzG1mwiytPadBt+VcmPQWcO5pi WxUI7biRYt4aLriuKeRpk94ai9+52KAk7Lz3KUWoyRwdZINqkI/aDZL6meWmcrOJWCUMW73e 4cMqK5XFnGqolhK4RQu+8IHkSXtmWui7LUeEvO/OwU0EXvts4wEQANCXyDOic0j2QKeyj/ga OD1oKl44JQfOgcyLVDZGYyEnyl6b/tV1mNb57y/YQYr33fwMS1hMj9eqY6tlMTNz+ciGZZWV YkPNHA+aFuPTzCLrapLiz829M5LctB2448bsgxFq0TPrr5KYx6AkuWzOVq/X5wYEM6djbWLc VWgJ3o0QBOI4/uB89xTf7mgcIcbwEf6yb/86Cs+jaHcUtJcLsVuzW5RVMVf9F+Sf/b98Lzrr 2/mIB7clOXZJSgtV79Alxym4H0cEZabwiXnigjjsLsp4ojhGgakgCwftLkhAnQT3oBLH/6ix 87ahawG3qlyIB8ZZKHsvTxbWte6c6xE5dmmLIDN44SajAdmjt1i7SbAwFIFjuFJGpsnfdQv1 OiIVzJ44kdRJG8kQWPPua/k+AtwJt/gjCxv5p8sKVXTNtIP/sd3EMs2xwbF8McebLE9JCDQ1 RXVHceAmPWVCq3WrFuX9dSlgf3RWTqNiWZC0a8Hn6fNDp26TzLbdo9mnxbU4I/3BbcAJZI9p 9ELaE9rw3LU8esKqRIfaZqPtrdm1C+e5gZa2gkmEzG+WEsS0MKtJyOFnuglGl1ZBxR1uFvbU VXhewCNoviXxkkPk/DanIgYB1nUtkPC+BHkJJYCyf9Kfl33s/bai34aaxkGXqpKv+CInARg3 fCikcHzYYWKaXS6HABEBAAHCwXwEGAEIACYCGwwWIQSH6ZrVEpascJjzbVq59+x3yCm/lgUC Z8H0qQUJDIjuxgAKCRC59+x3yCm/loAdD/wJCOhPp9711J18B9c4f+eNAk5vrC9Cj3RyOusH Hebb9HtSFm155Zz3xiizw70MSyOVikjbTocFAJo5VhkyuN0QJIP678SWzriwym+EG0B5P97h FSLBlRsTi4KD8f1Ll3OT03lD3o/5Qt37zFgD4mCD6OxAShPxhI3gkVHBuA0GxF01MadJEjMu jWgZoj75rCLG9sC6L4r28GEGqUFlTKjseYehLw0s3iR53LxS7HfJVHcFBX3rUcKFJBhuO6Ha /GggRvTbn3PXxR5UIgiBMjUlqxzYH4fe7pYR7z1m4nQcaFWW+JhY/BYHJyMGLfnqTn1FsIwP dbhEjYbFnJE9Vzvf+RJcRQVyLDn/TfWbETf0bLGHeF2GUPvNXYEu7oKddvnUvJK5U/BuwQXy TRFbae4Ie96QMcPBL9ZLX8M2K4XUydZBeHw+9lP1J6NJrQiX7MzexpkKNy4ukDzPrRE/ruui yWOKeCw9bCZX4a/uFw77TZMEq3upjeq21oi6NMTwvvWWMYuEKNi0340yZRrBdcDhbXkl9x/o skB2IbnvSB8iikbPng1ihCTXpA2yxioUQ96Akb+WEGopPWzlxTTK+T03G2ljOtspjZXKuywV Wu/eHyqHMyTu8UVcMRR44ki8wam0LMs+fH4dRxw5ck69AkV+JsYQVfI7tdOu7+r465LUfg== In-Reply-To: <20260810180956.2348280-1-almasrymina@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/10/26 8:09 PM, Mina Almasry wrote: > skb_zerocopy() fails to propagate the unreadable flag when copying > devmem fragments, causing target skbs to appear as readable memory. > > This patch fixes the flag propagation. Additionally, it returns -EFAULT > if standard payload is mixed with unreadable devmem fragments during > extraction, and clamps unreadable skb lengths in openvswitch > queue_userspace_packet() to avert truncated invalid payloads. > > Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags") > Cc: Pavel Begunkov > Cc: Stanislav Fomichev > Cc: Bobby Eshleman > Cc: Florian Westphal > Cc: Aaron Conole > Cc: Eelco Chaudron > Cc: Ilya Maximets > Signed-off-by: Mina Almasry > Reviewed-by: Pavel Begunkov > > --- > v2: > - Return -EFAULT when mixing unreadable and readable frags (Pavel). > - Clamp unreadable skb lengths for openvswitch queue drops (sashiko). > v1: https://lore.kernel.org/r/20260801125308.1342897-1-almasrymina@google.com > > Openvswitch maintainers: PTAL at the openvswitch changes closely. They > are reported by sashiko as an also-need part of this fix: > https://sashiko.dev/#/patchset/20260706155219.23757-1-fw%40strlen.de Hmm. FWIW, I do not see anything about openvswitch at that page. > diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c > index ae69b2cabab9e..7c663d7846174 100644 > --- a/net/openvswitch/datapath.c > +++ b/net/openvswitch/datapath.c > @@ -480,6 +480,8 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb, > } > > skb_len = min(skb->len, cutlen); > + if (!skb_frags_readable(skb)) > + skb_len = min_t(size_t, skb_len, skb_headlen(skb)); I'm not very familiar with the devmem and the unreadable frags, but if there is really no way to read 'skb_len' bytes of the packet, it must not be delivered to userspace. Delivering truncated packet will confuse ovs-vswitchd and the packet will be dropped or delivered truncated to the destination. We should return something like -EFAULT here and the caller will drop the packet (MISS upcall) or continue processing if the failure is not fatal (ACTION upcall). This practically makes devmem incompatible with OVS, I suppose, as upcalls are the primary mechanism for initial packet processing, before the datapath flows are installed. If there is a way to read this memory, we should make a full copy here. Best regards, Ilya Maximets.