From: Jann Horn jannh@google.com
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: e2ca90c276e1 ("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 --- drivers/net/usb/ax88179_178a.c | 68 +++++++++++++++++++++++------------------ 1 file changed, 39 insertions(+), 29 deletions(-)
--- a/drivers/net/usb/ax88179_178a.c +++ b/drivers/net/usb/ax88179_178a.c @@ -1369,59 +1369,69 @@ static int ax88179_rx_fixup(struct usbne 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_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; - } + if (pkt_len > skb->len) + return 0;
- ax_skb = skb_clone(skb, GFP_ATOMIC); - if (ax_skb) { + /* 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) + 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 *