From 8608d8575f01232c0f93a47d501d38e2e2f6e6ca Mon Sep 17 00:00:00 2001
From: Gordon Tetlow <gordon@FreeBSD.org>
Date: Wed, 5 Aug 2020 17:11:18 +0000
Subject: [PATCH] Fix memory corruption in USB network device drivers.

Approved by:	so
Security:	FreeBSD-SA-20:21.usb_net
Security:	CVE-2020-7459
---
 sys/dev/usb/net/if_cdceem.c | 17 +++++++++++++----
 sys/dev/usb/net/if_muge.c   | 11 +++++++++--
 sys/dev/usb/net/if_smsc.c   | 13 +++++++++++--
 3 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/sys/dev/usb/net/if_cdceem.c b/sys/dev/usb/net/if_cdceem.c
index ea92670e8f9..8bf6b041e4c 100644
--- a/sys/dev/usb/net/if_cdceem.c
+++ b/sys/dev/usb/net/if_cdceem.c
@@ -426,9 +426,10 @@ cdceem_handle_data(struct usb_xfer *xfer, uint16_t hdr, int *offp)
 	struct usb_ether *ue;
 	struct ifnet *ifp;
 	struct mbuf *m;
-	int actlen, off;
 	uint32_t computed_crc, received_crc;
-	uint16_t pktlen;
+	int pktlen;
+	int actlen;
+	int off;
 
 	off = *offp;
 	sc = usbd_xfer_softc(xfer);
@@ -442,7 +443,7 @@ cdceem_handle_data(struct usb_xfer *xfer, uint16_t hdr, int *offp)
 	    (hdr & CDCEEM_DATA_CRC) ? "valid" : "absent",
 	    pktlen);
 
-	if (pktlen < ETHER_HDR_LEN) {
+	if (pktlen < (ETHER_HDR_LEN + 4)) {
 		CDCEEM_WARN(sc,
 		    "bad ethernet frame length %d, should be at least %d",
 		    pktlen, ETHER_HDR_LEN);
@@ -466,6 +467,14 @@ cdceem_handle_data(struct usb_xfer *xfer, uint16_t hdr, int *offp)
 	}
 
 	pktlen -= 4; /* Subtract the CRC. */
+
+	if (pktlen > m->m_len) {
+		CDCEEM_WARN(sc, "buffer too small %d vs %d bytes",
+		    pktlen, m->m_len);
+		if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
+		m_freem(m);
+		return;
+	}
 	usbd_copy_out(pc, off, mtod(m, uint8_t *), pktlen);
 	off += pktlen;
 
@@ -512,7 +521,7 @@ cdceem_bulk_read_callback(struct usb_xfer *xfer, usb_error_t usb_error)
 		pc = usbd_xfer_get_frame(xfer, 0);
 		off = 0;
 
-		while (off < actlen) {
+		while ((off + sizeof(hdr)) <= actlen) {
 			usbd_copy_out(pc, off, &hdr, sizeof(hdr));
 			CDCEEM_DEBUG(sc, "hdr = %#x", hdr);
 			off += sizeof(hdr);
diff --git a/sys/dev/usb/net/if_muge.c b/sys/dev/usb/net/if_muge.c
index 6ea695e69ce..73b23fdf8fd 100644
--- a/sys/dev/usb/net/if_muge.c
+++ b/sys/dev/usb/net/if_muge.c
@@ -1167,9 +1167,9 @@ muge_bulk_read_callback(struct usb_xfer *xfer, usb_error_t error)
 	struct ifnet *ifp = uether_getifp(ue);
 	struct mbuf *m;
 	struct usb_page_cache *pc;
-	uint16_t pktlen;
 	uint32_t rx_cmd_a, rx_cmd_b;
 	uint16_t rx_cmd_c;
+	int pktlen;
 	int off;
 	int actlen;
 
@@ -1251,7 +1251,14 @@ muge_bulk_read_callback(struct usb_xfer *xfer, usb_error_t error)
 					    1);
 					goto tr_setup;
 				}
-
+				if (pktlen > m->m_len) {
+					muge_dbg_printf(sc,
+					    "buffer too small %d vs %d bytes",
+					    pktlen, m->m_len);
+					if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
+					m_freem(m);
+					goto tr_setup;
+				}
 				usbd_copy_out(pc, off, mtod(m, uint8_t *),
 				    pktlen);
 
diff --git a/sys/dev/usb/net/if_smsc.c b/sys/dev/usb/net/if_smsc.c
index cccf43acba1..f09dc421cf2 100644
--- a/sys/dev/usb/net/if_smsc.c
+++ b/sys/dev/usb/net/if_smsc.c
@@ -973,7 +973,7 @@ smsc_bulk_read_callback(struct usb_xfer *xfer, usb_error_t error)
 	struct mbuf *m;
 	struct usb_page_cache *pc;
 	uint32_t rxhdr;
-	uint16_t pktlen;
+	int pktlen;
 	int off;
 	int actlen;
 
@@ -999,6 +999,9 @@ smsc_bulk_read_callback(struct usb_xfer *xfer, usb_error_t error)
 			/* The frame header is always aligned on a 4 byte boundary */
 			off = ((off + 0x3) & ~0x3);
 
+			if ((off + sizeof(rxhdr)) > actlen)
+				goto tr_setup;
+
 			usbd_copy_out(pc, off, &rxhdr, sizeof(rxhdr));
 			off += (sizeof(rxhdr) + ETHER_ALIGN);
 			rxhdr = le32toh(rxhdr);
@@ -1027,7 +1030,13 @@ smsc_bulk_read_callback(struct usb_xfer *xfer, usb_error_t error)
 					if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
 					goto tr_setup;
 				}
-				
+				if (pktlen > m->m_len) {
+					smsc_dbg_printf(sc, "buffer too small %d vs %d bytes",
+					    pktlen, m->m_len);
+					if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
+					m_freem(m);
+					goto tr_setup;
+				}
 				usbd_copy_out(pc, off, mtod(m, uint8_t *), pktlen);
 
 				/* Check if RX TCP/UDP checksumming is being offloaded */
-- 
2.45.0