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net: usb: ax88179_178a: Fix out-of-bounds accesses in RX fixup

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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: e2ca90c276 ("ax88179_178a: ASIX AX88179_178A USB 3.0/2.0 to gigabit ethernet adapter driver")
Cc: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jann Horn 2022-01-26 14:14:52 +01:00 committed by Greg Kroah-Hartman
parent 117b4e96c7
commit 57bc3d3ae8
1 changed files with 38 additions and 28 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

66
drivers/net/usb/ax88179_178a.c
View file

@ -1468,58 +1468,68 @@ 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);
rx_hdr = get_unaligned_le32(skb_tail_pointer(skb));
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;
if (pkt_len > skb->len)
return 0;
/* 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_hdr & (AX_RXHDR_CRC_ERR | AX_RXHDR_DROP_ERR)) == 0) &&
pkt_len >= 2 + ETH_HLEN) {
bool last = (pkt_cnt == 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;
}
ax_skb = skb_clone(skb, GFP_ATOMIC);
if (ax_skb) {
if (last) {
ax_skb = skb;
} else {
ax_skb = skb_clone(skb, GFP_ATOMIC);
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 *