From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C8B1429CCA for ; Tue, 14 Jul 2026 20:58:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784062695; cv=none; b=k27Ot+Ifu2bqGKLuRJAWksHajqsVpjtfHSUreRmCe47En5bTjVpo62HW32JJKYcdNYz4APx+IbQjyoTC4JkCoXkDqK4krsrBhvynzBba/51Kegy4snLV/33UeTqdRf3vhOT4qK24FkMiqx2NVuyT2yniMwc9lSRjG0xe4Os4eug= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784062695; c=relaxed/simple; bh=ugFocKQNvJq5suQ2bGHSV0nqJNZHbZnZeHUn8h4L41k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RiHMmoYFQ3ib8Z/j4ygUFi+tphHciUwska/IIzBYtxHP+VtZ6fUoZ7zzhPW7u8j8pE4kHEuQ79Jl10iFff9XONnAgN6yn8K9J9SB9swHhdf7hHcOGHxhSk9cZrsWicffd1cE3cZH3U2SoQelcQAGmdtOcjLpVsgKoph6q73a1h4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=kWKn33aL; arc=none smtp.client-ip=91.218.175.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="kWKn33aL" Message-ID: <1fc10768-18c7-40f4-9287-250415c3e7a7@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784062680; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TdayDcoevcw1swGHvcsiPGuw7O5eij5Cwke7HcSMW9g=; b=kWKn33aLNzr3sotFHz5u2DOaBFLv4KJNytljEJAtWGkpmO//huga3KVLdteyIubYWCnn5I NYfCA+jPzEtAmwz6YaOvvRGJE81y6p7aEyYv2wTcfOeoPdixo88cWva/qxyesFtDzfua7i YEVaob3fpt7gp8wI97m5QXnyosKVcXQ= Date: Tue, 14 Jul 2026 21:57:47 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net v3] nfc: llcp: reject PDUs shorter than the LLCP header To: Doruk Tan Ozturk , david@ixit.cz Cc: horms@kernel.org, david.laight.linux@gmail.com, oe-linux-nfc@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260714164631.75068-1-doruk@0sec.ai> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Vadim Fedorenko In-Reply-To: <20260714164631.75068-1-doruk@0sec.ai> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 14.07.2026 17:46, Doruk Tan Ozturk wrote: > Every LLCP PDU begins with a two-byte header (DSAP/SSAP + PTYPE), but the > receive path never checked that a frame is at least LLCP_HEADER_SIZE bytes > before parsing it. > > nfc_llcp_rx_skb() reads the header via nfc_llcp_ptype()/nfc_llcp_dsap()/ > nfc_llcp_ssap(), which dereference pdu->data[0] and pdu->data[1], and a > CONNECT or CC PDU then computes > > tlv_array_len = skb->len - LLCP_HEADER_SIZE; > > as a size_t and hands it to the TLV walk. When the frame is shorter than > the header the subtraction wraps to a huge value and the walk runs far > past the buffer, an out-of-bounds read. > > A nearby NFC device can reach this without authentication; LLCP link > activation happens automatically after NFC-DEP. > > Guard the common receive choke point __nfc_llcp_recv(), shared by both the > target (nfc_llcp_data_received()) and initiator (nfc_llcp_recv()) paths, so > a short skb is dropped before the rx_work worker parses it. Use > pskb_may_pull() rather than a skb->len test so the two header bytes are > guaranteed to sit in the skb linear area even for a non-linear skb, > matching how the sibling NCI and HCI receive paths validate their headers. > > Reproduced with a KFENCE out-of-bounds read via /dev/virtual_nci on > linux-next. > > Found by 0sec automated security-research tooling (https://0sec.ai). > > Fixes: d646960f7986 ("NFC: Initial LLCP support") > Cc: stable@vger.kernel.org > Suggested-by: David Laight > Signed-off-by: Doruk Tan Ozturk > --- > v3: use pskb_may_pull() so the guard also covers non-linear skbs and > guarantees the header bytes are in the linear area (David Laight). > v2: move the guard into __nfc_llcp_recv() so both the target and > initiator receive paths are covered by a single check. > > diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c > index aed5fe1afef0..e3b2627cb089 100644 > --- a/net/nfc/llcp_core.c > +++ b/net/nfc/llcp_core.c > @@ -1565,6 +1565,11 @@ static void nfc_llcp_rx_work(struct work_struct *work) > > static void __nfc_llcp_recv(struct nfc_llcp_local *local, struct sk_buff *skb) > { > + if (!pskb_may_pull(skb, LLCP_HEADER_SIZE)) { > + kfree_skb(skb); > + return; > + } > + > local->rx_pending = skb; > timer_delete(&local->link_timer); > schedule_work(&local->rx_work); Reviewed-by: Vadim Fedorenko