From: Greg Kroah-Hartman Date: Thu, 9 Apr 2026 15:18:14 +0000 (+0200) Subject: NFC: digital: Bounds check NFC-A cascade depth in SDD response handler X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=46ce8be2ced389bccd84bcc04a12cf2f4d0c22d1;p=thirdparty%2Fkernel%2Flinux.git NFC: digital: Bounds check NFC-A cascade depth in SDD response handler The NFC-A anti-collision cascade in digital_in_recv_sdd_res() appends 3 or 4 bytes to target->nfcid1 on each round, but the number of cascade rounds is controlled entirely by the peer device. The peer sets the cascade tag in the SDD_RES (deciding 3 vs 4 bytes) and the cascade-incomplete bit in the SEL_RES (deciding whether another round follows). ISO 14443-3 limits NFC-A to three cascade levels and target->nfcid1 is sized accordingly (NFC_NFCID1_MAXSIZE = 10), but nothing in the driver actually enforces this. This means a malicious peer can keep the cascade running, writing past the heap-allocated nfc_target with each round. Fix this by rejecting the response when the accumulated UID would exceed the buffer. Commit e329e71013c9 ("NFC: nci: Bounds check struct nfc_target arrays") fixed similar missing checks against the same field on the NCI path. Cc: Simon Horman Cc: Kees Cook Cc: Thierry Escande Cc: Samuel Ortiz Fixes: 2c66daecc409 ("NFC Digital: Add NFC-A technology support") Cc: stable Assisted-by: gregkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman Link: https://patch.msgid.link/2026040913-figure-seducing-bd3f@gregkh Signed-off-by: Jakub Kicinski --- diff --git a/net/nfc/digital_technology.c b/net/nfc/digital_technology.c index 63f1b721c71d..ae63c5eb06fa 100644 --- a/net/nfc/digital_technology.c +++ b/net/nfc/digital_technology.c @@ -424,6 +424,12 @@ static void digital_in_recv_sdd_res(struct nfc_digital_dev *ddev, void *arg, size = 4; } + if (target->nfcid1_len + size > NFC_NFCID1_MAXSIZE) { + PROTOCOL_ERR("4.7.2.1"); + rc = -EPROTO; + goto exit; + } + memcpy(target->nfcid1 + target->nfcid1_len, sdd_res->nfcid1 + offset, size); target->nfcid1_len += size;