[PATCH net 2/2] NFC: digital: Bounds check Felica response before sensf_res memcpy

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

A malicious NFC peer can send a SENSF_RES that is longer than the
NFC_SENSF_RES_MAXSIZE (18 byte) sensf_res field in the onstack struct
nfc_target.  digital_in_recv_sensf_res() validates that the response is
at least DIGITAL_SENSF_RES_MIN_LENGTH bytes but applies no upper bound
before memcpy(target.sensf_res, sensf_res, resp->len) is called,
allowing a stack buffer overflow with attacker-controlled length and
content.

Commit e329e71013c9 ("NFC: nci: Bounds check struct nfc_target arrays")
fixed identical missing checks for the same target->sensf_res field on
the NCI path; the Digital Protocol path was never patched.

Fix this all up by just rejecting responses that exceed
NFC_SENSF_RES_MAXSIZE.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Thierry Escande <thierry.escande@linux.intel.com>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Fixes: 8c0695e4998d ("NFC Digital: Add NFC-F technology support")
Cc: stable <stable@kernel.org>
Assisted-by: gregkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/nfc/digital_technology.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/nfc/digital_technology.c b/net/nfc/digital_technology.c
index ae63c5eb06fa..e18bdb231352 100644
--- a/net/nfc/digital_technology.c
+++ b/net/nfc/digital_technology.c
@@ -774,6 +774,11 @@ static void digital_in_recv_sensf_res(struct nfc_digital_dev *ddev, void *arg,
 
 	skb_pull(resp, 1);
 
+	if (resp->len > NFC_SENSF_RES_MAXSIZE) {
+		rc = -EPROTO;
+		goto exit;
+	}
+
 	memset(&target, 0, sizeof(struct nfc_target));
 
 	sensf_res = (struct digital_sensf_res *)resp->data;
-- 
2.53.0