[PATCH net v2] nfc: digital: clamp SENSF_RES length to the destination buffer

digital_in_recv_sensf_res() memcpy()s resp->len bytes from a remote
NFC-F device response into the NFC_SENSF_RES_MAXSIZE-byte target.sensf_res
field without an upper-bound check. A nearby malicious NFC-F device can
send an oversized SENSF_RES response to overflow the stack-local struct
nfc_target.

Clamp resp->len to NFC_SENSF_RES_MAXSIZE before the copy.

Found by 0sec automated security-research tooling (https://0sec.ai).

Fixes: 8c0695e4998d ("NFC Digital: Add NFC-F technology support")
Cc: [email protected]
Signed-off-by: Doruk Tan Ozturk <[email protected]>
---
v2:
 - Clamp resp->len with min_t() before the copy (Alexander Lobakin).
 - Add Fixes: tag and Cc: stable (Alexander Lobakin).
 - Frame as a stack buffer overflow (saved-return overwrite not demonstrated).
 net/nfc/digital_technology.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/nfc/digital_technology.c b/net/nfc/digital_technology.c
index ae63c5eb0..ae6487c10 100644
--- a/net/nfc/digital_technology.c
+++ b/net/nfc/digital_technology.c
@@ -778,6 +778,8 @@ static void digital_in_recv_sensf_res(struct nfc_digital_dev *ddev, void *arg,
 
 	sensf_res = (struct digital_sensf_res *)resp->data;
 
+	resp->len = min_t(unsigned int, resp->len, NFC_SENSF_RES_MAXSIZE);
+
 	memcpy(target.sensf_res, sensf_res, resp->len);
 	target.sensf_res_len = resp->len;
 
-- 
2.53.0