From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f178.google.com (mail-pg1-f178.google.com [209.85.215.178]) (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 9A3F538839C for ; Mon, 20 Apr 2026 08:28:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776673703; cv=none; b=WrUblwdIYwP393BZGfaTdw6mSBBz2A/3G080+pKacj4e/WL8KPAz98BO4zOsm7oEkxrPR7y76k2+gXz06MpVSJmldxrmNKXqWoDDW4NdLoJJOHXPQB2MsomxkkW9QO1xTVxwo3JfoMI56wL+IXKS8iEfEGLYU909vP0uLRJKQO4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776673703; c=relaxed/simple; bh=M4+77cOcU68W9THBSjVg8Xbcol4HAaJurQC7Ojwff/Q=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=YcN8jaPPYcpMnFWdJWT8IddG/gE8wlHHkfixYVohX75IuqzZK82Kfs1wcw91DiZRP6ZmroTcvrCeivz7Qkd4Nteu3jVffd9+oajvzTmH/PuBoGKiXANKhuHKGQwNC9mmRoPidXJOK9E0NPFsp0YnYgOTrPY9EWIO+M/UPEc0HgI= 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=kI4qao6R; arc=none smtp.client-ip=209.85.215.178 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="kI4qao6R" Received: by mail-pg1-f178.google.com with SMTP id 41be03b00d2f7-c7358a7a8d1so1724360a12.3 for ; Mon, 20 Apr 2026 01:28:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776673702; x=1777278502; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=I5eoEKPMkgwA6eleJzc6ZMHbLGT+Vc5FYW2VP2CKDVk=; b=kI4qao6RuCvFlgAFnbZcP2xRyvEZWpCy172pXAjRLeXzSHYH8v7xU4cuwy8uJuoQ9Y CRA/bKYfvGvsL0Te6dralKu/WeunTn59NfGU4FsEfuDiIC/6CO4FPHQaf64FGupuSfjz nBhCGr/CpkMngVhD69ceDbq7bURS1SMHRlLh6hWT1ppNbXBQQRBCfClrmSNfoTB06zkW 1yfnz8+P8Rw47GyphpjsEqXC4o3ipnmNfovu5sIbz14aYHqL7ChxLfFkx8G329aooqmE Uw7vnfed5j2zJwMy7tJ2sPKqZlvggHXFmguHz+yjBvTKLAj9D1q8W85I2q6KbztT6Jrj WYwA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776673702; x=1777278502; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=I5eoEKPMkgwA6eleJzc6ZMHbLGT+Vc5FYW2VP2CKDVk=; b=cdL03zDW9j2b6vqIAjQXa0wM6HAy/9JZcsnz/wkePuO+dOqPRSJR2RYpf1NugakcTa nmJ1KtrnsguWF2D38pqzSWz6bDHZVcxXQBpQS2ufnTFDRAJ8UyXpy3vNKPzTJhpuZHUr bPQOnZqa6oRIHlx7IjuAYb0NxOGMQj66IzY747WqRPOGJD5HJCXFrmdCtXxybXCHZfYN DFnv0+Q8zwFjtVDm1I2K4tFyxvpTWjxaj+NUH0Htf7ESmUoAWUt6UQ7sIYoLr0fcW5Vv kwMD1QSp/o+otUYT58mb+KnTpmGRlHY6uq+EMbOMJunzWfZvlFUdSn9ILAiC+OtwB+Nc Vuig== X-Forwarded-Encrypted: i=1; AFNElJ+HxRZsbbiFiXGQkFwfKYA9HqXiwKVfGGogjocVo2le2upay1MVQnht8YCeGZK+Rc9XCmTARcs=@vger.kernel.org X-Gm-Message-State: AOJu0YzYpUpvCimKtyAiitGqgvHklu5UGdsO4x8HJbqckZL87oGl3f4U Hjs9l4taHz2YyVhQTPnNL+3sIy/mSPLtiDeOLc0rTKmvQAPX2XL9fvb1 X-Gm-Gg: AeBDietDsTV8knDWsynvtXM/L/69aquzGyIYG/SAoAVEpmCOOqOtEPHqnq0/vn/fMRd r0e9UWSV6WDQkTbpFz49OLww/uCJT55qRboZ/EkLw9sGSdEWAvs6ckfwiI50i4SEO0yMoA2TfmL vcH5mTl3f5GtEFnvTLJCgNJ0btfum8xWXvT0bPKY5DAizmeRGznKs+LmYAFyngrTlF+qpKkPvsj PE10OGDj2J0ixNpEK8+yr7vLyLAj3dszefRtODH/TESaYN4hhLPq+Zjzu91muDaPbP9cuopPxej 6DpOSWUd9FTbQelkUVsBeIX5BbvmP9I9C8tidAIUT7kRc8PyxD8k19a/wmh6x4LCcx7M7hFEvtC ALVKdG6vw5KTxdB4B0qp+EMYe/jY54FAmev0aDQ5/MJk65EFPw2ulVJRvpPvGp66Xx+EHjXVPOY 9GvjnU2uiwOUqpYlcD6lohPGzeftWfjltM7QNSEcF2D5RbSCeDJWSUao8cDerrzwrhMn3xc5pKA kThZ3FXaUDZZ/rsNzg= X-Received: by 2002:a05:6a20:7d9e:b0:366:2447:6778 with SMTP id adf61e73a8af0-3a08d93e320mr13740453637.53.1776673701880; Mon, 20 Apr 2026 01:28:21 -0700 (PDT) Received: from KERNELXING-MB0.tencent.com ([43.132.141.20]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c798b56a758sm1728010a12.18.2026.04.20.01.28.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2026 01:28:20 -0700 (PDT) From: Jason Xing To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, bjorn@kernel.org, magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com, sdf@fomichev.me, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing Subject: [PATCH net v2 1/8] xsk: reject sw-csum UMEM binding to IFF_TX_SKB_NO_LINEAR devices Date: Mon, 20 Apr 2026 16:27:58 +0800 Message-Id: <20260420082805.14844-2-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260420082805.14844-1-kerneljasonxing@gmail.com> References: <20260420082805.14844-1-kerneljasonxing@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jason Xing skb_checksum_help() is a common helper that writes the folded 16-bit checksum back via skb->data + csum_start + csum_offset, i.e. it relies on the skb's linear head and fails (with WARN_ONCE and -EINVAL) when skb_headlen() is 0. AF_XDP generic xmit takes two very different paths depending on the netdev. Drivers that advertise IFF_TX_SKB_NO_LINEAR (e.g. virtio_net) skip the "copy payload into a linear head" step on purpose as a performance optimisation: xsk_build_skb_zerocopy() only attaches UMEM pages as frags and never calls skb_put(), so skb_headlen() stays 0 for the whole skb. For these skbs there is simply no linear area for skb_checksum_help() to write the csum into - the sw-csum fallback is structurally inapplicable. The patch tries to catch this and reject the combination with error at setup time. Rejecting at bind() converts this silent per-packet failure into a synchronous, actionable -EOPNOTSUPP at setup time. HW csum and launch_time metadata on IFF_TX_SKB_NO_LINEAR drivers are unaffected because they do not call skb_checksum_help(). Without the patch, every descriptor carrying 'XDP_TX_METADATA | XDP_TXMD_FLAGS_CHECKSUM' produces: 1) a WARN_ONCE "offset (N) >= skb_headlen() (0)" from skb_checksum_help(), 2) sendmsg() returning -EINVAL without consuming the descriptor (invalid_descs is not incremented), 3) a wedged TX ring: __xsk_generic_xmit() does not advance the consumer on non-EOVERFLOW errors, so the next sendmsg() re-reads the same descriptor and re-hits the same WARN until the socket is closed. Closes: https://lore.kernel.org/all/20260419045822.843BFC2BCAF@smtp.kernel.org/#t Fixes: 30c3055f9c0d ("xsk: wrap generic metadata handling onto separate function") Signed-off-by: Jason Xing --- net/xdp/xsk_buff_pool.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c index 37b7a68b89b3..c2521b6547e3 100644 --- a/net/xdp/xsk_buff_pool.c +++ b/net/xdp/xsk_buff_pool.c @@ -169,6 +169,9 @@ int xp_assign_dev(struct xsk_buff_pool *pool, if (force_zc && force_copy) return -EINVAL; + if (pool->tx_sw_csum && (netdev->priv_flags & IFF_TX_SKB_NO_LINEAR)) + return -EOPNOTSUPP; + if (xsk_get_pool_from_qid(netdev, queue_id)) return -EBUSY; -- 2.41.3