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Commit 1668781e authored by Jann Horn's avatar Jann Horn Committed by Greg Kroah-Hartman
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net: usb: ax88179_178a: Fix out-of-bounds accesses in RX fixup 



commit 57bc3d3ae8c14df3ceb4e17d26ddf9eeab304581 upstream.

ax88179_rx_fixup() contains several out-of-bounds accesses that can be
triggered by a malicious (or defective) USB device, in particular:

 - The metadata array (hdr_off..hdr_off+2*pkt_cnt) can be out of bounds,
   causing OOB reads and (on big-endian systems) OOB endianness flips.
 - A packet can overlap the metadata array, causing a later OOB
   endianness flip to corrupt data used by a cloned SKB that has already
   been handed off into the network stack.
 - A packet SKB can be constructed whose tail is far beyond its end,
   causing out-of-bounds heap data to be considered part of the SKB's
   data.

I have tested that this can be used by a malicious USB device to send a
bogus ICMPv6 Echo Request and receive an ICMPv6 Echo Reply in response
that contains random kernel heap data.
It's probably also possible to get OOB writes from this on a
little-endian system somehow - maybe by triggering skb_cow() via IP
options processing -, but I haven't tested that.

Fixes: e2ca90c2 ("ax88179_178a: ASIX AX88179_178A USB 3.0/2.0 to gigabit ethernet adapter driver")
Cc: stable@kernel.org
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4d7edade

drivers/net/usb/ax88179_178a.c

+39 −29
Original line number Diff line number Diff line
@@ -1373,59 +1373,69 @@ static int ax88179_rx_fixup(struct usbnet *dev, struct sk_buff *skb) 
	u16 hdr_off;

	u32 *pkt_hdr;



	/* This check is no longer done by usbnet */

	if (skb->len < dev->net->hard_header_len)

	/* At the end of the SKB, there's a header telling us how many packets

	 * are bundled into this buffer and where we can find an array of

	 * per-packet metadata (which contains elements encoded into u16).

	 */

	if (skb->len < 4)

		return 0;



	skb_trim(skb, skb->len - 4);

	memcpy(&rx_hdr, skb_tail_pointer(skb), 4);

	le32_to_cpus(&rx_hdr);



	pkt_cnt = (u16)rx_hdr;

	hdr_off = (u16)(rx_hdr >> 16);



	if (pkt_cnt == 0)

		return 0;



	/* Make sure that the bounds of the metadata array are inside the SKB

	 * (and in front of the counter at the end).

	 */

	if (pkt_cnt * 2 + hdr_off > skb->len)

		return 0;

	pkt_hdr = (u32 *)(skb->data + hdr_off);



	while (pkt_cnt--) {

	/* Packets must not overlap the metadata array */

	skb_trim(skb, hdr_off);



	for (; ; pkt_cnt--, pkt_hdr++) {

		u16 pkt_len;



		le32_to_cpus(pkt_hdr);

		pkt_len = (*pkt_hdr >> 16) & 0x1fff;



		/* Check CRC or runt packet */

		if ((*pkt_hdr & AX_RXHDR_CRC_ERR) ||

		    (*pkt_hdr & AX_RXHDR_DROP_ERR)) {

			skb_pull(skb, (pkt_len + 7) & 0xFFF8);

			pkt_hdr++;

			continue;

		}

		if (pkt_len > skb->len)

			return 0;



		if (pkt_cnt == 0) {

			skb->len = pkt_len;

			/* Skip IP alignment pseudo header */

			skb_pull(skb, 2);

			skb_set_tail_pointer(skb, skb->len);

			skb->truesize = pkt_len + sizeof(struct sk_buff);

			ax88179_rx_checksum(skb, pkt_hdr);

			return 1;

		}

		/* Check CRC or runt packet */

		if (((*pkt_hdr & (AX_RXHDR_CRC_ERR | AX_RXHDR_DROP_ERR)) == 0) &&

		    pkt_len >= 2 + ETH_HLEN) {

			bool last = (pkt_cnt == 0);



			if (last) {

				ax_skb = skb;

			} else {

				ax_skb = skb_clone(skb, GFP_ATOMIC);

		if (ax_skb) {

				if (!ax_skb)

					return 0;

			}

			ax_skb->len = pkt_len;

			/* Skip IP alignment pseudo header */

			skb_pull(ax_skb, 2);

			skb_set_tail_pointer(ax_skb, ax_skb->len);

			ax_skb->truesize = pkt_len + sizeof(struct sk_buff);

			ax88179_rx_checksum(ax_skb, pkt_hdr);



			if (last)

				return 1;



			usbnet_skb_return(dev, ax_skb);

		} else {

			return 0;

		}



		skb_pull(skb, (pkt_len + 7) & 0xFFF8);

		pkt_hdr++;

		/* Trim this packet away from the SKB */

		if (!skb_pull(skb, (pkt_len + 7) & 0xFFF8))

			return 0;

	}

	return 1;

}



static struct sk_buff *