From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) (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 CFEB138A72B for ; Fri, 15 May 2026 12:30:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778848254; cv=none; b=f3LHWlt93EQf3I0b5TeqdQJxzIDLzPViOBYtMUt9EopqpkqfqidfCwq4ZrDF7EsD8JLVb/Q55lEy2JggCHK2t//orAbbPnIYppMUIHebAIlbXol4sJRkaT4K51CsJchjBmUzg92Y0CO0UIAPVJnOimO95CoYhJlwxpd8fTBwIqA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778848254; c=relaxed/simple; bh=IQhPw3IiVr6zqqu4CRDJ4j0to08qx8xv/NfQTLHz18Q=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ZjiQxp7uL/J/4ufVgnBMF61/vQIQy3JptnNmps0eV6OTUC01xhd37QU3oD3nP0BNtOWYP4HAFFqp4nxipIAB4slzmIiBkgDqoU0qTmdXOms48IP4bpUL5g6bGtfwHMJAVPV8X8LwIEuuqmcKreSDs8K6BducjGzS7nXw4etg2rU= 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=VmZ5oAa0; arc=none smtp.client-ip=209.85.216.44 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="VmZ5oAa0" Received: by mail-pj1-f44.google.com with SMTP id 98e67ed59e1d1-367cbac9cb1so7014144a91.3 for ; Fri, 15 May 2026 05:30:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778848252; x=1779453052; 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=BjcyuuQLuaEXuRzmmB8Nl+fj/3MjgdhxLsDyrZCPoIc=; b=VmZ5oAa062zttJ9lqGRpazmhleIs+UUxv+Ahb18sePzrK7ie9MsVsMqx2/yYY64FK5 u5t9BOAhUEvL0RHdZEn4shuex1MU7j7qN0/v3R7Hx6rjyApHPUBLCIdMK/SD7KGf4PUD 3mtyBWsXDvRAX/Ufz+2q4zErzQxY5BtSrIffcXSXPfxLTSHbVKY2RYAvOxA/ifecwzde O1W9jEiXFpe5uwxgDUTrOiBRUNmO7D6oEHvcvTs0xMyBPnTNLyxpIOliPxF9nl3R2Lgq DHudh7g3pkCrEDR7DV06IJRiGkZ5EWB7iNT0kSCWtEq176hKeNmEbM6efP8ktA8Wx5Js 3QmA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778848252; x=1779453052; 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=BjcyuuQLuaEXuRzmmB8Nl+fj/3MjgdhxLsDyrZCPoIc=; b=GRT+VwHkzSCd98XoEtCbdIuJXyQd2iloak7uqbmOq/7aBqFAcqU2rA+D/PccZIQuny q168xbQpGcpDnrnhoTdiKnPom0Y1C60z9h2F6rivDSUu0W8GuvtDberT14ATl+kuK47M NZ6xWfGz8KTEB1UG6cW5FWV1jTswhNpVM5VOdf101mcXFFJjnYaUwLW85YtHoqJbFU30 KOcXSA/AuxttZYHwehAm9qp+UGyTHNzBhdAtE0XuTKfkYAeqqqeCcKlO9XQ237UUHU+K Udl3lDuNiFD/QTV1r8FRQmnWBolwbudaRdsXWDB/FXPvre2P/ixw8LHEcu8P55Y0z+tR AKQw== X-Forwarded-Encrypted: i=1; AFNElJ9yiZF9sh7agwysBpqWwOEP0+3ou72AoCYC3yMkaHSi3cJhYD90Py6Odne1AEcXyxg55qE6uH8=@vger.kernel.org X-Gm-Message-State: AOJu0YwwtmoZQgd8SaPm3PQTAg3P1hcVfJZR+jQ88VftZdZU1tk0Rr3Y NCet9lNGzhIpDYsSwWXwVpglksZXLEEoMj7mhShCJx0LIpJAZwqsVXvH X-Gm-Gg: Acq92OG1ST7XV4hsae1MRotOFzl6wjyq0x/U1qg1GUC5xZTRDZmdvz6x8gFIXcjj4DC xHHlGNbvlJiojE5bMeFHgbkjHlxUYXr4mlSwcXpF6HaNTKYYSE1at0jmQ/ZhVoxxgRyUQxsbDUf Y+uZYoCaWrYmp3yJfgxRHhkTsiLdRCdyaHHukxYR9g67X0qsW7i4Rim6Wb8Ap71waXdKQCSr4V3 F8Mn81KSdIzi+OSYLcxE6//gw0G0a3e3tZ/lpXa7CkNepzw8R29klo0v48qGEQVdBbO7CzxscH2 ZHZjX9c0Fox0UGRA7zevObvUQAMVj1S4T6SDUtJrZfxrknH7QI7GAm1jM9ApgcVtbUB0F+kEOS7 rWjvDT63t17qf/cSDqv3ppPQzFb8koj/+k9JBAnAG5+gd+5IGqbsmJDKqYs61DQ7oiqjnhkzvmR u85+kIOWV5XNc0BQ2wRRPLbXTVcEqPqT1Z2/qA9DbGBLt7WYucf3EMrIbM4S/iS7IvUFrTzzVgA tW7NDkHLC7CgObB0ejdrq3e0Kflg50= X-Received: by 2002:a17:902:a515:b0:2bc:7eee:200a with SMTP id d9443c01a7336-2bd7e8c31admr30757915ad.22.1778848251961; Fri, 15 May 2026 05:30:51 -0700 (PDT) Received: from KERNELXING-MC1.tencent.com ([2408:8207:1923:2c20:a48a:1116:aa2d:1122]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2bd5cfe492asm60348885ad.48.2026.05.15.05.30.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 May 2026 05:30:51 -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, horms@kernel.org, andrew+netdev@lunn.ch Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing Subject: [PATCH net v2 3/5] xsk: drain continuation descs after overflow in xsk_build_skb() Date: Fri, 15 May 2026 20:30:16 +0800 Message-Id: <20260515123018.80147-4-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260515123018.80147-1-kerneljasonxing@gmail.com> References: <20260515123018.80147-1-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 When a multi-buffer packet exceeds MAX_SKB_FRAGS and triggers -EOVERFLOW, only the current descriptor is released from the TX ring. The remaining continuation descriptors of the same packet stay in the ring. Since xs->skb is set to NULL after the drop, the TX loop picks up these leftover frags and misinterprets each one as the beginning of a new packet, corrupting the packet stream. Fix this by adding a drain_cont flag to xdp_sock. When overflow occurs and the dropped descriptor has XDP_PKT_CONTD set, the flag is raised. The main TX loop in __xsk_generic_xmit() then handles continuation descriptors one at a time: each gets a normal CQ reservation (with backpressure), its address is submitted to the completion queue, and the descriptor is released from the TX ring. When the last fragment (without XDP_PKT_CONTD) is processed, the flag is cleared and the function returns -EOVERFLOW so the next call starts with a fresh budget for normal packets. This reuses the existing CQ backpressure and budget mechanisms, so if the CQ is full the function returns -EAGAIN and userspace drains the CQ before retrying. Zero buffer leakage, zero packet stream corruption. Closes: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/ Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path") Signed-off-by: Jason Xing --- include/net/xdp_sock.h | 1 + net/xdp/xsk.c | 22 ++++++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h index 23e8861e8b25..1958d19d9925 100644 --- a/include/net/xdp_sock.h +++ b/include/net/xdp_sock.h @@ -80,6 +80,7 @@ struct xdp_sock { * call of __xsk_generic_xmit(). */ struct sk_buff *skb; + bool drain_cont; struct list_head map_list; /* Protects map_list */ diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 1cc14cb415f3..f98a9553e536 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -936,6 +936,8 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, xs->tx->invalid_descs++; } xskq_cons_release(xs->tx); + if (xp_mb_desc(desc)) + xs->drain_cont = true; } else { /* Let application retry */ xsk_cq_cancel_locked(xs->pool, 1); @@ -982,6 +984,26 @@ static int __xsk_generic_xmit(struct sock *sk) goto out; } + if (unlikely(xs->drain_cont)) { + unsigned long flags; + u32 idx; + + spin_lock_irqsave(&xs->pool->cq_prod_lock, flags); + idx = xskq_get_prod(xs->pool->cq); + xskq_prod_write_addr(xs->pool->cq, idx, desc.addr); + xskq_prod_submit_n(xs->pool->cq, 1); + spin_unlock_irqrestore(&xs->pool->cq_prod_lock, flags); + + xs->tx->invalid_descs++; + xskq_cons_release(xs->tx); + if (!xp_mb_desc(&desc)) { + xs->drain_cont = false; + err = -EOVERFLOW; + goto out; + } + continue; + } + skb = xsk_build_skb(xs, &desc); if (IS_ERR(skb)) { err = PTR_ERR(skb); -- 2.41.3