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Sat, 11 Jul 2026 00:30:14 -0700 (PDT) Received: from PeakBook-Mini.tail8e484.ts.net ([178.197.218.188]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47ad69519c2sm71148700f8f.37.2026.07.11.00.30.13 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 11 Jul 2026 00:30:14 -0700 (PDT) From: Doruk Tan Ozturk To: david@ixit.cz, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: horms@kernel.org, oe-linux-nfc@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Doruk Tan Ozturk Subject: [PATCH net] nfc: llcp: guard against short PDUs in nfc_llcp_rx_skb() Date: Sat, 11 Jul 2026 09:30:12 +0200 Message-ID: <20260711073012.71066-1-doruk@0sec.ai> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit nfc_llcp_recv_connect() and nfc_llcp_recv_cc() pass skb->len - LLCP_HEADER_SIZE to nfc_llcp_parse_connection_tlv() as a size_t. When skb->len < LLCP_HEADER_SIZE the subtraction wraps around to a huge value and the TLV walk runs past the skb. nfc_llcp_rx_skb() applied no minimum-length check before dispatching, so a PDU shorter than the 2-byte LLCP header reached these call sites. Drop such PDUs up front; every LLCP PDU carries the header, so no valid frame is shorter (a SYMM PDU is exactly LLCP_HEADER_SIZE bytes). Found by 0sec (https://0sec.ai) using automated source analysis. Fixes: d646960f7986 ("NFC: Initial LLCP support") Cc: stable@vger.kernel.org Assisted-by: 0sec:claude-opus-4-8 Signed-off-by: Doruk Tan Ozturk --- net/nfc/llcp_core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c index aed5fe1afef0..e3b3077e0e83 100644 --- a/net/nfc/llcp_core.c +++ b/net/nfc/llcp_core.c @@ -1481,6 +1481,9 @@ static void nfc_llcp_rx_skb(struct nfc_llcp_local *local, struct sk_buff *skb) { u8 dsap, ssap, ptype; + if (skb->len < LLCP_HEADER_SIZE) + return; + ptype = nfc_llcp_ptype(skb); dsap = nfc_llcp_dsap(skb); ssap = nfc_llcp_ssap(skb); -- 2.43.0