From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f48.google.com (mail-pj1-f48.google.com [209.85.216.48]) (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 BE21433557B for ; Sat, 18 Apr 2026 04:57:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776488247; cv=none; b=qsiuviap9ti3uUexAqYU23JgzRUEAJT1TbQMgnGuCW9WWspiEDnxwew3HtM+BwxBzCz/6l2XZ/OEcZN1ZJ7lrblcguu0Q7v5pBf3qKeOoj9g90EKCq+hcMmhsFoUjiF3V9T0srxXrk+X2S19YjjzXrFa7OxR35YTvpnMwYW9S8w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776488247; c=relaxed/simple; bh=noCuVUbIZS87iKo2soZQK++66nTPA97Hb0ZZSl1yh4c=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=lLqF0jsDekIOF9f8hAMYGyUjH0lDfdeodimROAivqVD+ZojE56M2CmbCD1JlbeA/XyubJhnjerbvV5P6PDrzVZnDlCB0/pI6Zv0qNFBBaYQebbbUj9X0Vso6STy1ZrIm8zyoip7ZZ7Qq+W9bGUtLX+Onzs9668KITiQ3Ja10g08= 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=HV+oVsiS; arc=none smtp.client-ip=209.85.216.48 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="HV+oVsiS" Received: by mail-pj1-f48.google.com with SMTP id 98e67ed59e1d1-356337f058aso891076a91.2 for ; Fri, 17 Apr 2026 21:57:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776488245; x=1777093045; 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=M7fYuN5x2Np/CFxQoQV61Iy8WpLzu2WAC3PFJmjW8IU=; b=HV+oVsiSFw0VpyRxOcDe5TSVvWFCqV3+uGtt1fJi0vFJUOuSgiWRl+7jpG/yIA9dtY CPkfycJpaaD7Uh3z9X6x9durrJszTxyObZeETNPAt5OMpcynZlHk+w02qbdrVNn93UH+ yKwHnfuXOpK2cElsTG1s58RJe/I3sAczToB9jEsDY2vUTXcG5g3dCdKiS2HjSdYORpPc e9hjpE68MIKKILL7bPSKywwiU6Bz9c/r+CpsifsJlVNu95WJr8LZ9/Cy/D5nnSe2MrkY 4uHvy422SduGbVJaQzERV5HbhguKa6unCOKuLTPk0qLsEXw/RrRIJaVQ8RwXKwvMzOsZ GDGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776488245; x=1777093045; 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=M7fYuN5x2Np/CFxQoQV61Iy8WpLzu2WAC3PFJmjW8IU=; b=O5qetoFTCkymdRMUxotCA0SECs1+QTDB6+nN282da4aF0GPI/8cdaAwe6bHfXWkmKq EkSNmni9w8ZCOBJIFGCtvty2vDDfkKV59ZM5l7CgBjiFFOBmRmuijfbml215uz0/keOO /3CLmBcx1KOcm2Axe/sZj0y3o1MwfW/XP9+RpgTpRKCTCYI4pcEmUmO2e0bBcT4XMLfO xRRGUFFKQyr+hQ/sy1SYcaoEm+h2o6byDnDkw0F9r732AvKLnLOapCAeD14P3CSw1KRV N7DhiS5RstiGdk/i5peuvc5A9MomM2ZwdTD4sFyNqV4xJZE3f5chzKa2/RqEvZ+00jAY ulTw== X-Gm-Message-State: AOJu0YzEsYU2i7ZAaL7AQz42/W85lwDP7mN/2vQrjduAMXidZa94FmQS 31nOMX8eR0wNl8GPWDJNNxAewF9bmvYCdmCFcZ8RKAwfZ/dwd/GiocVh X-Gm-Gg: AeBDieu6NQwgHDnJVAJzGQdxUHJsTvSeryjH+MnCV+QwEjQ2Wevcol053cyGlpzjaGt cHiS+08vMfQnPzynOE43TslzKg8jXHoZBJ9+oZfHu7qhXgu5lkNLUitQfZFD/3Yd/AY8gIumIyH pQJmhotcVBcCPeRB4eP9hQdiTHit4zXQtxMkbFvbyL937qQjdxIpnu3FfaDAxvhZhAK495xVeNa NDIqe7fPHUjY3gCcbO2GXmsefznw9enPojg6EBzkQ1A9ZdW6IQsF3Qe3IzbEPTcseXNJqBu9pMa VLOAS/CYx1p+uY44xNWICttWj/GSXLiVWUI1smKeft8tCSCbsKqjAtBjPTN2AkRQR+tuR07BhNz wZiJKD1CYe7ilgc7BqeQZYNk1biKKl8zw2PLQJdMZktTIpj+yqxH+ZvejZ4zPo4jmbQcEAlIV06 bJtf3zoIhr7E9fW3ridnxLBThCqQf2QgOMS9riNPy1CMVJKzWRAe7pf+t88LDmXofc+a1e/KnEW XYD52g8FQ== X-Received: by 2002:a17:90b:4c52:b0:35f:b647:d98a with SMTP id 98e67ed59e1d1-361403c3412mr6182207a91.5.1776488245131; Fri, 17 Apr 2026 21:57:25 -0700 (PDT) Received: from KERNELXING-MC1.tencent.com ([2408:8207:1924:8520:35f1:286f:2ada:eed0]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3614195a92asm3502377a91.10.2026.04.17.21.57.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2026 21:57:24 -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 3/4] xsk: handle NULL dereference of the skb without frags issue Date: Sat, 18 Apr 2026 12:56:43 +0800 Message-Id: <20260418045644.28612-4-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260418045644.28612-1-kerneljasonxing@gmail.com> References: <20260418045644.28612-1-kerneljasonxing@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jason Xing When a first descriptor (xs->skb == NULL) triggers -EOVERFLOW in xsk_build_skb_zerocopy (e.g., MAX_SKB_FRAGS exceeded), the free_err EOVERFLOW handler unconditionally dereferences xs->skb via xsk_inc_num_desc(xs->skb) and xsk_drop_skb(xs->skb), causing a NULL pointer dereference. In the patch 2/4, the skb is already freed by kfree_skb() inside xsk_build_skb_zerocopy for the first-descriptor case, so we only need to do the bookkeeping: cancel the one reserved CQ slot and account for the single invalid descriptor. Guard the existing xsk_inc_num_desc/xsk_drop_skb calls with an xs->skb check (for the continuation case), and add an else branch for the first-descriptor case that manually cancels the CQ slot and increments invalid_descs by one. Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path") Signed-off-by: Jason Xing --- net/xdp/xsk.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 5d3dbb118730..2918b773aa84 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -898,9 +898,14 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, kfree_skb(skb); if (err == -EOVERFLOW) { - /* Drop the packet */ - xsk_inc_num_desc(xs->skb); - xsk_drop_skb(xs->skb); + if (xs->skb) { + /* Drop the packet */ + xsk_inc_num_desc(xs->skb); + xsk_drop_skb(xs->skb); + } else { + xsk_cq_cancel_locked(xs->pool, 1); + xs->tx->invalid_descs++; + } xskq_cons_release(xs->tx); } else { /* Let application retry */ -- 2.41.3