From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) (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 4B0992DB7BA for ; Fri, 24 Apr 2026 05:38:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777009112; cv=none; b=M4tauL5oYw3cH7E7gF+h4dbcRAcUWCiBvqQjZ1cHWRl4AEdeTQxcT8KvdG+Ha6fWb2yiAhDTKv4qoCetoks5Uzco6kZ/ySH63IZE2n3mFPJl2v/BFgSYoJK9N/hCcgHQy+/5VuVujuBuSb+LneSZqQqCwv0zIeTP0beh0U/beZo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777009112; c=relaxed/simple; bh=fctOOu8ihanad4KwnadnhQVcL0yq7+8B+O+aK7WYNr0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=DRXtx/Jm0eCfGkURthDghj2+NQnANyi8QIieaNJIqRTzD2ES/tfXe8gUNppH5lzkqrZI/3MabxNeXnTw/BHj+6xvMkGJSW3YpGtXHjp6L0JzpB6Lvu5cSHn7QpCmq6a5m26WjW2HHlOkJI5qLT78BelxAAWmP2oCW/Oxf2ptgGI= 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=Q9CRg717; arc=none smtp.client-ip=209.85.214.178 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="Q9CRg717" Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-2b458ca2296so47566675ad.0 for ; Thu, 23 Apr 2026 22:38:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777009111; x=1777613911; 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=i0ej40ghKn8TLZMMNc2ToDzMeEQCp4B7994Wm2iXNOY=; b=Q9CRg717t7I19+981t/+Nqu1X1tYncjidgdVL6rRcdCjg7iz+MhYt84VgWyHZo+H9W xifiwBM8yHMaksoth/4TeDOwCkZ/fzdzygN5U2v5j6kxyyHANcoLyEhzcY7+mZXgCL/w kcgK3nP/YNBFULoVvQZ4MjscUTzdfgzhi1+U8puQCCJlXROup2IEHAaEY+C59+DL0I3p lsRVwtzaSLdxNwBnDzcsDu9qojE/So7X8CcbTEihbVOoDUl9ESK+fIncfbmBz+PP0men k+U5WjMtejKqMwBAuGEbnoGaqg/FgQ43Nyf0mPcJN9ILMR79by3OCoNvDEkEvLLnmJBV o2Sw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777009111; x=1777613911; 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=i0ej40ghKn8TLZMMNc2ToDzMeEQCp4B7994Wm2iXNOY=; b=QNCDTHDIj5HZqubvTiMkINcvcmuh5ZSH5stdCfmhEpxRkYMR/TeIyBzy//Qul3RrsN dPwSBt9xPzCXAZhtX/1iZVdb6RFop9iV3IZO3Ds7Px65Wwt5VbOSSdTf0x98IWgSgEpy PYGuPAnkhCms6EGTegurHQTaXIcal4rCXcbGPVxcZ1aSrpwoZaSpbR8nrYrS8EGpQb6Z HX+nPKonIio72UWYTrHo6Ghjh7uOtLEgpDWjBUDZee6QXAHpNdxSag9mlI3AnOc5EY9j op+lh+WN+akJKfJdaWP3XheMKpZzcFksCVnePVmSH9mQFBv7boz/EmM0TTGPIZzGeJk5 duzw== X-Forwarded-Encrypted: i=1; AFNElJ8YL1XAhVLXBOMB9+LHoB2KmP1+gaT3Y2ydk7r8DHomxln8r6ExBliM4ZuYAI9jFHgyoxLkvfs=@vger.kernel.org X-Gm-Message-State: AOJu0YwjBtn7fP+0WVmBHMyxVdDKeaUTlgKoHXu9ePMwre17AFyMLmf+ 3hzajmxfBvXqASHhqACvUFW7hu0LdpdsbgQ3IKges63cKEOIqCDgtImg X-Gm-Gg: AeBDies81T4iAFnNb5YqaKhJRoxwYWTJ9DoEaALbZYNGPGPQYoLI1HLgrA/ZPMPyyhu IGx2ZZUUdgz8rnV+Nyt69aoL8pgB4nPHUpmVon0CAgJ9cxG4H7sp/gp7j1L7VHpeKcoW5lDhq2R 8hv6X00ZL5OAhNIEiaDXf/DA1X0+XozzISYa35IKi/GpWuSNXfOj5Yjyfz+lr9ZqfpMCRGoHH7A 6NlM2GXxKrhqUBq9DIz4X/9qvZXw050vQTUB6elMzuJ5dCa5bcFMwv1UvD4KIoUZoDpK/zBejL7 8GMw+z+nzeHjzCQQil4haYrRQjV+QZn/J0SLIHp5kF7j+hMGPE9Z9ZorqXOyR9MopTq+n1x6LTI NxHxh6k9sKkm12lij2gdZA7PZGgC4GsVPykPjajb0sdlJzm4VAoFKPUWV1pSRDJD2G5J3hcpS/p 410orQG64X6dZcb0TPNNYSV7pBCsoZ8cjisqY6uCQcygXqg2kWiWNxRk25utLXO76PeA7Q3Q/e/ HTR3AqITsOXOrC9nsLEDD1ILgUW78VtngSn6KYo X-Received: by 2002:a17:902:f645:b0:2b4:5ff5:e51a with SMTP id d9443c01a7336-2b5f9f51abcmr301815925ad.19.1777009110586; Thu, 23 Apr 2026 22:38:30 -0700 (PDT) Received: from KERNELXING-MB0.tencent.com ([43.132.141.25]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b5fab405f3sm209444725ad.78.2026.04.23.22.38.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Apr 2026 22:38:29 -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, aleksander.lobakin@intel.com Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing Subject: [PATCH net v4 1/8] xsk: reject sw-csum UMEM binding to IFF_TX_SKB_NO_LINEAR devices Date: Fri, 24 Apr 2026 13:38:09 +0800 Message-Id: <20260424053816.27965-2-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260424053816.27965-1-kerneljasonxing@gmail.com> References: <20260424053816.27965-1-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") Acked-by: Stanislav Fomichev 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