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 7511C3A5442 for ; Wed, 22 Apr 2026 03:37:08 +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=1776829029; cv=none; b=Zd/G2lPiSAeZdv9l8U0OPUdcWVp8r1A+R1D53ihkVwE2cdrigcXSMUIJ0+/QzdOYbAg+ZlIQN5joKuE8CzB8onhMSjdoVIer7mmThceO1vW5rj1APZrs9lNthN2EBCFt3Vle65c/oXh+L/eXHD+2zqZZB0mzBzieuEwN07Upo1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776829029; c=relaxed/simple; bh=TlmfMj0oSjpUNpbiocpFSZqid0mqlfXPvbNwh7NE30k=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=X0O4F7+jQcuRRT2MR08XBrigEjnubQ6YenHl7fvN3k1A420G3tcxh7nTnckbrTAv5Ci1x3l/XCbR0pDWw1S9nc8tYb8+PwAJ/cKE8lUvFYn0bT/bmC9HATdugnT6QkTT+QJgZbgASf1hbt9JoZc4Ku9WHHlcC5OttZrvQ10fSKo= 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=pKlrXjeF; 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="pKlrXjeF" Received: by mail-pf1-f174.google.com with SMTP id d2e1a72fcca58-82cebbdbdccso3012537b3a.1 for ; Tue, 21 Apr 2026 20:37:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776829028; x=1777433828; 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=WUXScEQ9v1TBc9CvHH+nPgE6m6kMqTjtcGXW0lXDNGM=; b=pKlrXjeF5ey5zWVUWiZfOVG/O+T9l8WBMvV0wzLiSfYRrpxeL9P7AcSxRNdzcf5fAq 0WNGnLxwVN95gVPFKbQGIX1kEXwEIQ21LvhMxrkXRyRGXuCnFFlq++F2Tm83vY7nmLZA vQGTUh0yBa+BA5NPeg37iYVZcCaoGaFuuT1MpLq1wm6JbefCIDBuQEAiv2KSuUEtl55v lcomm1YjYv1BzCb2/3gcquRzn5douJs7RGmPtOxp2gEej+lUrOhW3gOibfnZCvmZpIpP 0okmhAMug8Vo552oZR9hzs2W6HfgvHoDf9Sb2h1QAyk9IEu96lsRBCUNsOpJ+3I8UwnP fxSA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776829028; x=1777433828; 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=WUXScEQ9v1TBc9CvHH+nPgE6m6kMqTjtcGXW0lXDNGM=; b=PBlSXTE4OZZQ38L4a4kcKf3wx4f9pkeaychOi1N1H9Y3Zf60vDjKBJj/7h20DMFsE+ ee59wDSY3jiHTXijW0qeyisU0FBlotqfwLZ4T0j8/fobfcc38i4SX8TwJ9NVlt4ErPLS 28GWCJfT900WfQ5bdygZG1h0YxnOvc+ci0wJonmNNBFeGvUtKArvHGKhyLUddbCL9bxq XDcPSlvaK8GSAtXzxPMepIwGf6p1RAnq+Pk0UgiCEqCca/QWiUSrZjjYWB0anC+xitPS lH39FJyWTdCUDCn1KAqxQMHR8gt0Uq/e1kQFYXToMdAANCfMKbBwQAyXt6IXHMDiBIvI mVAA== X-Gm-Message-State: AOJu0YzL0YzIt5PIkuZcjLy3XbbO/pLDa/5oOFrpfu6Hox7GjYrzz3UZ cyrfNwT7/bCJlWJJz0FrYiOtJiSoLo1YBiQsH43G+H982UZ/hfIovL0Y X-Gm-Gg: AeBDiev9oJZ3ZKdykcirpXWP5T2YWVCkcWVdgLHwxh8PwPO09c3CbUsycrqf1h8P/BA z1bs0/o1HDQebLWz+Tvc8O6EnLvg/2CQumSos3yGKAMBSSANfmYBMW2KCgQs4K+FZhegNXviKg+ RIJcTIUrrsQ4Fw3ElXzVpVrig1sDnJMfj6IKZgAkedaLCHg+Y4ryBaGIzDzikEfJx05RUHzNcra KDFSi6ZJBiImES+N5JAhmzOs9QVZ2tjP6q/zjTxXWc8+bAUgtb0JPxZbIb5r8b6hGe+Vmt0K7P0 m8Bt0AVrVxj0+cDrhJWPrYEFQ8iGyEqZjzyFsRULr8aaxu2FzQAU8/y0rf+pz/xPhzgSp4ZsyUy hvk8GFYBHqaIRjZcR83XDxnLi9wKCqxVhHxXY/+f8ioeSFZhswzwVEJlGq3s/0F0fBADxGZZ/eF jy8X+x7EbDbTQPmE0b9RGeD1fNyIkjyJucGXBR00xgoVTWI/SqkXqExsYaGYbKQCSmD5EHnc6+X iGopbek X-Received: by 2002:a05:6a00:3cce:b0:82f:6b70:5a71 with SMTP id d2e1a72fcca58-82f8b507fbfmr16996956b3a.21.1776829027662; Tue, 21 Apr 2026 20:37:07 -0700 (PDT) Received: from KERNELXING-MB0.tencent.com ([43.132.141.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8e981c07sm18355473b3a.1.2026.04.21.20.37.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2026 20:37:07 -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 2/8] xsk: handle NULL dereference of the skb without frags issue Date: Wed, 22 Apr 2026 11:36:44 +0800 Message-Id: <20260422033650.68457-3-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: 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 this series, 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") Acked-by: Stanislav Fomichev 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 6149f6a79897..6521604f8d42 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -893,9 +893,14 @@ 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