From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f174.google.com (mail-pf1-f174.google.com [209.85.210.174]) (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 4E2693A451E for ; Wed, 22 Apr 2026 03:37:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776829038; cv=none; b=OKgEq9K+uZVqQkoVjzssbCk4TUCSRWYvRhj4LF8Eh76kZpfianYieZXDGcHFfi6TT3xTXQYhMzCUb/B3+TNylYSDDLzXZyjkmYXNusF4d9S3wusuV3OS3oII+ACPiR5MSpvjDx+Q4jvVad3FyVTfzXmSNQEvCzwU5zX3hSthUcM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776829038; c=relaxed/simple; bh=iptCJ/bHKRj1fMFQE+A5aKdO5Z99CRwurcu7O1XGAlw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=jBazccuwkGvo2oyW50WSZkLCP7fOYsfSiFq/B/OXiwo8Rqa5iXCOaUV1H4zDCVQ0e0gEsuEBxv8owFnCAnttpCN7u5hyKpCoyuT3WTIteiKfh4rYRyjFpAIBk40Sp+7ss+oAWOjwdA9PBoNoLIykZ9OCNnfFQEm5vf+Nh1au3Fk= 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=aBKVPhoc; arc=none smtp.client-ip=209.85.210.174 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="aBKVPhoc" Received: by mail-pf1-f174.google.com with SMTP id d2e1a72fcca58-82fa8d6425bso1509183b3a.0 for ; Tue, 21 Apr 2026 20:37:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776829037; x=1777433837; 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=l5FNK2dMAt1AUCbwembDz3q9hbJSbopjTGmkhaK/v7M=; b=aBKVPhocvp/3B/zZFwdh3D7S11kDoao5ILRc/A+cbTjyFo45Rb7YlkB+oj4PLxiLPj 9Ra6uVx5KI7mrExvJTvv5f+90Dmj90ZSUqSEpfiZBEVxKfN2drL16dx20OfPEXE6Yu3I WuRNZfYkcecQpYKIUR1caTG+9fE+bpMz8auLFEFkQOZRdm3uudWcHfYyU5CosDgIc91+ Y53WUbYRJPjpf+WtKTEUapqyxzTuoU6hHtIn4mxPMozuj4fVr96rWIkPeSAn2qeIyfYh W4YH28uVrHv9ClmeHv+GMGOJ70BmQt741ANwBXBHE6nJX7D/BpcEeIxw2+RfuyIRbcAY dhrg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776829037; x=1777433837; 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=l5FNK2dMAt1AUCbwembDz3q9hbJSbopjTGmkhaK/v7M=; b=Tcaqg4s+nbeMf0uWwlvqJM3YyWp1lTvzqWmqmNvtSE2BN4NVWr6IfN1uCMpDnsUO1T gGLblWOcLRDivbgjK5B3jMJo/PEilJvppYR4CuvDOvPAZiUvxjjVrBPQWxYrRtP1pzaZ a7CFSI8CNgnmHuaSoSjVJSYjmVeQXUUzwoALd6BRT/QS6ucOwqlAxnMKz0XFn5CjGVkH CQYdJ9LVXrhQHsenKHVLBRRuaFaj0OP7kOVZcSANoXM2RCEk7B0EBSV4Oy6FECxlnuck 3QQPlRHSfVRzqCnlGN3UhOFv/3Rukuj/Kzh/VFMfiFf35NlD4RXUl4bvQw6E69ImUFVi kxLg== X-Forwarded-Encrypted: i=1; AFNElJ9cRl9vHztQIRqGvCPURq2KWPYTWPRAQrh2MHRzq5U6GSa3quwfRXvb7reVfTQtXGcrj6+cufk=@vger.kernel.org X-Gm-Message-State: AOJu0Yy2Yygpd88ck8Zdhp4y3kMheljGW4mHI9gMJ17VvB4C6bEezEeI 24AcKP8CHroqHeV5KumrK75wBdWkqvyomUTNhQEvkp8EI2FgOHdtanbu X-Gm-Gg: AeBDietx6AJmLoQaO4D/jVas0IlSoYi/aQStRMIii7gCi7UXik3ymPZQkmmqTKhertK CFeoNdc7hdLokbxdpvjvmbi4z00cDmp/On0KxIKM+1yJ8/CrQ1Wpnbih3aDAmwuCyfzDeN4iqK2 DBlMRJbzRoHSmKWSBGBfq8mbwxphXwUt9A6W03FjHa8XX0u1xPsDxmA2yKdFyYEGuYm1P3PT2I2 dJGS3JZEgGmvNZdPpx1E9ox9hsh+zE1ziUDvKkk1UsvwEi2cqeniqd676mAlitK/rJwVQCthsQ1 mwh2LDN8n4RO1uqTaP5qEEKjSSiiQla95oX5FiYEfOIFMNw2bQhcDIfIULxKcpFaONP1hDUCkG5 70QFdlyXCl6YAFHWBbzxcKHx2D4UQzY7DCHy7Zcd9PsKmLcjVXUYoMzI2vkxWi2v6gutS05X2PD HHbVytNZDlgwQgjHs4C54gSNd+7nD2MBSSK7nEbJeviHYodWqcgj0tYavXnwTv2tg2pAUBnE8jC u+aR66EyOeI7MPszZg= X-Received: by 2002:a05:6a00:2311:b0:82c:dd31:b83d with SMTP id d2e1a72fcca58-82f8c936e47mr22442349b3a.38.1776829036722; Tue, 21 Apr 2026 20:37:16 -0700 (PDT) Received: from KERNELXING-MB0.tencent.com ([43.132.141.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8e981c07sm18355473b3a.1.2026.04.21.20.37.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2026 20:37:16 -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 v3 4/8] xsk: prevent CQ desync when freeing half-built skbs in xsk_build_skb() Date: Wed, 22 Apr 2026 11:36:46 +0800 Message-Id: <20260422033650.68457-5-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260422033650.68457-1-kerneljasonxing@gmail.com> References: <20260422033650.68457-1-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 Once xsk_skb_init_misc() has been called on an skb, its destructor is set to xsk_destruct_skb(), which submits the descriptor address(es) to the completion queue and advances the CQ producer. If such an skb is subsequently freed via kfree_skb() along an error path - before the skb has ever been handed to the driver - the destructor still runs and submits a bogus, half-initialized address to the CQ. Postpone the init phase when we believe the allocation of first frag is successfully completed. Before this init, skb can be safely freed by kfree_skb(). Closes: https://lore.kernel.org/all/20260419045822.843BFC2BCAF@smtp.kernel.org/ Fixes: c30d084960cf ("xsk: avoid overwriting skb fields for multi-buffer traffic") Signed-off-by: Jason Xing --- net/xdp/xsk.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index d23d1b14b8b4..88ec6d2cbbcf 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -739,8 +739,6 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, return ERR_PTR(err); skb_reserve(skb, hr); - - xsk_skb_init_misc(skb, xs, desc->addr); if (desc->options & XDP_TX_METADATA) { err = xsk_skb_metadata(skb, buffer, desc, pool, hr); if (unlikely(err)) @@ -834,7 +832,6 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, if (unlikely(err)) goto free_err; - xsk_skb_init_misc(skb, xs, desc->addr); if (desc->options & XDP_TX_METADATA) { err = xsk_skb_metadata(skb, buffer, desc, xs->pool, hr); @@ -884,6 +881,8 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, } } + if (!xs->skb) + xsk_skb_init_misc(skb, xs, desc->addr); xsk_inc_num_desc(skb); return skb; -- 2.41.3