[PATCH] nfc: pn533: fix OOB read in pn533_acr122_is_rx_frame_valid()

[Deepanshu Kartikey]

frame->ccid.datalen is read directly from the USB response frame
and used, unchecked, as an index into frame->data[]. A malicious or
malfunctioning device can set this field to an arbitrary value,
causing the driver to read far outside the received buffer.

Bound ccid.datalen against the maximum possible ACR122 frame size
before using it, and reject values less than 2 to avoid the
"datalen - 2" underflowing.

Fixes: 9815c7cf22da ("NFC: pn533: Separate physical layer from the core implementation")
Reported-by: syzbot+1853daab1a47603d4678@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=1853daab1a47603d4678
Tested-by: syzbot+1853daab1a47603d4678@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>
---
 drivers/nfc/pn533/usb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/nfc/pn533/usb.c b/drivers/nfc/pn533/usb.c
index efb07f944fce..d08d3b0df988 100644
--- a/drivers/nfc/pn533/usb.c
+++ b/drivers/nfc/pn533/usb.c
@@ -322,6 +322,11 @@ static bool pn533_acr122_is_rx_frame_valid(void *_frame, struct pn533 *dev)
 	if (!frame->ccid.datalen)
 		return false;
 
+	if (frame->ccid.datalen < 2 ||
+	    frame->ccid.datalen > PN533_ACR122_FRAME_MAX_PAYLOAD_LEN +
+	    PN533_ACR122_RX_FRAME_TAIL_LEN)
+		return false;
+
 	if (frame->data[frame->ccid.datalen - 2] == 0x63)
 		return false;
 
-- 
2.43.0