[PATCH v3] nfc: microread: validate target discovery payload lengths

microread_target_discovered() parses target discovery payloads from
skb->data according to the HCI gate. The fixed field offsets and UID
copies were checked only against the destination nfc_target buffers, not
against the actual skb length.

Validate that each gate-specific payload contains the fixed fields and
UID bytes before reading or copying them.

Fixes: cfad1ba87150 ("NFC: Initial support for Inside Secure microread")
Cc: [email protected]
Assisted-by: Codex:gpt-5
Signed-off-by: Pengpeng Hou <[email protected]>
---
Changes since v2:
https://lore.kernel.org/all/[email protected]/
- no code changes
- revalidate the patch against current mainline
- add the required coding-assistant attribution

Changes since v1:
https://lore.kernel.org/all/[email protected]/
- add the Fixes tag and stable Cc requested during review
- rebase onto the current net tree

 drivers/nfc/microread/microread.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/nfc/microread/microread.c b/drivers/nfc/microread/microread.c
index 4149c5d735bd..dfa2490db545 100644
--- a/drivers/nfc/microread/microread.c
+++ b/drivers/nfc/microread/microread.c
@@ -483,13 +483,19 @@ static void microread_target_discovered(struct nfc_hci_dev *hdev, u8 gate,
 
 	switch (gate) {
 	case MICROREAD_GATE_ID_MREAD_ISO_A:
+		if (skb->len <= MICROREAD_EMCF_A_LEN) {
+			r = -EINVAL;
+			goto exit_free;
+		}
+
 		targets->supported_protocols =
 		      nfc_hci_sak_to_protocol(skb->data[MICROREAD_EMCF_A_SAK]);
 		targets->sens_res =
 			 be16_to_cpu(*(u16 *)&skb->data[MICROREAD_EMCF_A_ATQA]);
 		targets->sel_res = skb->data[MICROREAD_EMCF_A_SAK];
 		targets->nfcid1_len = skb->data[MICROREAD_EMCF_A_LEN];
-		if (targets->nfcid1_len > sizeof(targets->nfcid1)) {
+		if (targets->nfcid1_len > sizeof(targets->nfcid1) ||
+		    targets->nfcid1_len > skb->len - MICROREAD_EMCF_A_UID) {
 			r = -EINVAL;
 			goto exit_free;
 		}
@@ -497,13 +503,19 @@ static void microread_target_discovered(struct nfc_hci_dev *hdev, u8 gate,
 		       targets->nfcid1_len);
 		break;
 	case MICROREAD_GATE_ID_MREAD_ISO_A_3:
+		if (skb->len <= MICROREAD_EMCF_A3_LEN) {
+			r = -EINVAL;
+			goto exit_free;
+		}
+
 		targets->supported_protocols =
 		      nfc_hci_sak_to_protocol(skb->data[MICROREAD_EMCF_A3_SAK]);
 		targets->sens_res =
 			 be16_to_cpu(*(u16 *)&skb->data[MICROREAD_EMCF_A3_ATQA]);
 		targets->sel_res = skb->data[MICROREAD_EMCF_A3_SAK];
 		targets->nfcid1_len = skb->data[MICROREAD_EMCF_A3_LEN];
-		if (targets->nfcid1_len > sizeof(targets->nfcid1)) {
+		if (targets->nfcid1_len > sizeof(targets->nfcid1) ||
+		    targets->nfcid1_len > skb->len - MICROREAD_EMCF_A3_UID) {
 			r = -EINVAL;
 			goto exit_free;
 		}
@@ -511,11 +523,21 @@ static void microread_target_discovered(struct nfc_hci_dev *hdev, u8 gate,
 		       targets->nfcid1_len);
 		break;
 	case MICROREAD_GATE_ID_MREAD_ISO_B:
+		if (skb->len < MICROREAD_EMCF_B_UID + 4) {
+			r = -EINVAL;
+			goto exit_free;
+		}
+
 		targets->supported_protocols = NFC_PROTO_ISO14443_B_MASK;
 		memcpy(targets->nfcid1, &skb->data[MICROREAD_EMCF_B_UID], 4);
 		targets->nfcid1_len = 4;
 		break;
 	case MICROREAD_GATE_ID_MREAD_NFC_T1:
+		if (skb->len < MICROREAD_EMCF_T1_UID + 4) {
+			r = -EINVAL;
+			goto exit_free;
+		}
+
 		targets->supported_protocols = NFC_PROTO_JEWEL_MASK;
 		targets->sens_res =
 			le16_to_cpu(*(u16 *)&skb->data[MICROREAD_EMCF_T1_ATQA]);
@@ -523,6 +545,11 @@ static void microread_target_discovered(struct nfc_hci_dev *hdev, u8 gate,
 		targets->nfcid1_len = 4;
 		break;
 	case MICROREAD_GATE_ID_MREAD_NFC_T3:
+		if (skb->len < MICROREAD_EMCF_T3_UID + 8) {
+			r = -EINVAL;
+			goto exit_free;
+		}
+
 		targets->supported_protocols = NFC_PROTO_FELICA_MASK;
 		memcpy(targets->nfcid1, &skb->data[MICROREAD_EMCF_T3_UID], 8);
 		targets->nfcid1_len = 8;

base-commit: dac3e89a2c90c2feeb471e1f22a2512ad424b792
-- 
2.50.1 (Apple Git-155)