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Sat, 11 Jul 2026 00:13:05 -0700 (PDT) Received: from PeakBook-Mini.tail8e484.ts.net ([178.197.218.188]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493f2e77c2esm87910115e9.2.2026.07.11.00.13.03 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 11 Jul 2026 00:13:04 -0700 (PDT) From: Doruk Tan Ozturk To: David Heidelberg Cc: oe-linux-nfc@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net] nfc: st21nfca: validate ATR_REQ length against the received frame Date: Sat, 11 Jul 2026 09:13:01 +0200 Message-ID: <20260711071301.58071-1-doruk@0sec.ai> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" st21nfca_tm_recv_atr_req() checks that the received ATR_REQ frame is at least ST21NFCA_ATR_REQ_MIN_SIZE and that the self-declared atr_req->length is at least sizeof(struct st21nfca_atr_req), but never checks that atr_req->length does not exceed the actual received length (skb->len). st21nfca_tm_send_atr_res() then trusts the declared length: gb_len =3D atr_req->length - sizeof(struct st21nfca_atr_req); ... memcpy(atr_res->gbi, atr_req->gbi, gb_len); so an RF peer that sends a short frame but sets atr_req->length larger than the frame makes gb_len exceed the general bytes actually present, and the memcpy reads out of bounds past the received skb. Those bytes are placed in the ATR_RES and sent back to the peer (kernel-memory disclosure to a proximity attacker); a larger declared length is an out-of-bounds read (DoS). Reject frames whose declared length exceeds the received length. The adjacent nfc_tm_activated() path in the same function already derives its general-bytes length from skb->len rather than the declared field. Found by 0sec (https://0sec.ai) using automated source analysis; the missing bound is evident from source. Compile-tested. Fixes: 1892bf844ea0 ("NFC: st21nfca: Adding P2P support to st21nfca in Init= iator & Target mode") Cc: stable@vger.kernel.org Assisted-by: 0sec:claude-opus-4-8 Signed-off-by: Doruk Tan Ozturk Reviewed-by: Simon Horman --- drivers/nfc/st21nfca/dep.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/nfc/st21nfca/dep.c b/drivers/nfc/st21nfca/dep.c index 3425b68f0ddc..a5fab4fd5129 100644 --- a/drivers/nfc/st21nfca/dep.c +++ b/drivers/nfc/st21nfca/dep.c @@ -205,6 +205,9 @@ static int st21nfca_tm_recv_atr_req(struct nfc_hci_dev = *hdev, if (atr_req->length < sizeof(struct st21nfca_atr_req)) return -EPROTO; =20 + if (atr_req->length > skb->len) + return -EPROTO; + r =3D st21nfca_tm_send_atr_res(hdev, atr_req); if (r) return r; --=20 2.43.0