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Date: Mon, 20 Jun 2022 03:45:35 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Jose Alonso' <joalonsof@...il.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH v2] net: usb: ax88179_178a: ax88179_rx_fixup corrections
From: Jose Alonso
> Sent: 19 June 2022 01:54
>
> corrections:
> - the size check of the bounds of the metadata array.
> - the handling of the metadata array.
> The current code is allways exiting with return 0
> while trying to access pkt_hdr out of metadata array and
> generating RX Errors.
> - avoid changing the skb->data content (reverse bytes) in case
> of big-endian. le32_to_cpus(pkt_hdr)
>
> Tested with: 0b95:1790 ASIX Electronics Corp. AX88179 Gigabit Ethernet
>
> Signed-off-by: Jose Alonso <joalonsof@...il.com>
>
> ---
>
> diff --git a/drivers/net/usb/ax88179_178a.c b/drivers/net/usb/ax88179_178a.c
> index 4704ed6f00ef..d2f868dd3c10 100644
> --- a/drivers/net/usb/ax88179_178a.c
> +++ b/drivers/net/usb/ax88179_178a.c
> @@ -1445,18 +1445,18 @@ static void ax88179_unbind(struct usbnet *dev, struct usb_interface *intf)
> }
>
> static void
> -ax88179_rx_checksum(struct sk_buff *skb, u32 *pkt_hdr)
> +ax88179_rx_checksum(struct sk_buff *skb, u32 pkt_hdr_val)
> {
> skb->ip_summed = CHECKSUM_NONE;
>
> /* checksum error bit is set */
> - if ((*pkt_hdr & AX_RXHDR_L3CSUM_ERR) ||
> - (*pkt_hdr & AX_RXHDR_L4CSUM_ERR))
> + if ((pkt_hdr_val & AX_RXHDR_L3CSUM_ERR) ||
> + (pkt_hdr_val & AX_RXHDR_L4CSUM_ERR))
> return;
>
> /* It must be a TCP or UDP packet with a valid checksum */
> - if (((*pkt_hdr & AX_RXHDR_L4_TYPE_MASK) == AX_RXHDR_L4_TYPE_TCP) ||
> - ((*pkt_hdr & AX_RXHDR_L4_TYPE_MASK) == AX_RXHDR_L4_TYPE_UDP))
> + if (((pkt_hdr_val & AX_RXHDR_L4_TYPE_MASK) == AX_RXHDR_L4_TYPE_TCP) ||
> + ((pkt_hdr_val & AX_RXHDR_L4_TYPE_MASK) == AX_RXHDR_L4_TYPE_UDP))
> skb->ip_summed = CHECKSUM_UNNECESSARY;
> }
>
> @@ -1467,11 +1467,47 @@ static int ax88179_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
> u32 rx_hdr;
> u16 hdr_off;
> u32 *pkt_hdr;
> + u32 pkt_hdr_val;
>
> /* 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).
> */
> +
> + /* SKB contents for current firmware:
> + * <packet 1> <padding>
> + * ...
> + * <packet N> <padding>
> + * <per-packet metadata entry 1> <dummy header>
> + * ...
> + * <per-packet metadata entry N> <dummy header>
> + * <padding2> <rx_hdr>
> + *
> + * where:
> + * <packet N> contains pkt_len bytes:
> + * 2 bytes of IP alignment pseudo header
> + * packet received
> + * <per-packet metadata entry N> contains 4 bytes:
> + * pkt_len and fields AX_RXHDR_*
> + * <padding> 0-7 bytes to terminate at
> + * 8 bytes boundary (64-bit).
> + * <padding2> 4 bytes
> + * <dummy-header> contains 4 bytes:
> + * pkt_len=0 & AX_RXHDR_DROP_ERR
> + * <rx-hdr> contains 4 bytes:
> + * pkt_cnt and hdr_off (offset of
> + * <per-packet metadata entry 1>)
> + *
> + * pkt_cnt is number of entrys in the per-packet metadata.
> + * In current firmware there is 2 entrys per packet.
> + * The first points to the packet and the
> + * second is a dummy header.
> + * This was done probably to align fields in 64-bit and
> + * maintain compatibility with old firmware.
> + * This code assumes that <dummy header> and <padding2> are
> + * optional.
> + */
> +
> if (skb->len < 4)
> return 0;
> skb_trim(skb, skb->len - 4);
> @@ -1485,51 +1521,63 @@ static int ax88179_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
> /* 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)
> + if (pkt_cnt * 4 + hdr_off > skb->len)
> return 0;
> pkt_hdr = (u32 *)(skb->data + hdr_off);
>
> /* Packets must not overlap the metadata array */
> skb_trim(skb, hdr_off);
>
> - for (; ; pkt_cnt--, pkt_hdr++) {
> + for (; pkt_cnt > 0; pkt_cnt--, pkt_hdr++) {
> u16 pkt_len;
> + u16 pkt_len_buf;
>
> - le32_to_cpus(pkt_hdr);
> - pkt_len = (*pkt_hdr >> 16) & 0x1fff;
> + pkt_hdr_val = get_unaligned_le32(pkt_hdr);
> + pkt_len = (pkt_hdr_val >> 16) & 0x1fff;
> + pkt_len_buf = (pkt_len + 7) & 0xfff8;
>
> - if (pkt_len > skb->len)
> + /* Skip dummy header used for alignment
> + */
> + if (pkt_len == 0)
> + continue;
> +
> + if (pkt_len_buf > skb->len)
> return 0;
>
> /* 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);
You've 'lost' this lie.
IIRC the 'skb' are allocated with 64k buffer space.
I'm not at all sure how the buffer space of skb that are cloned
into multiple rx buffers are supposed to be accounted for.
Does this driver ever copy the data for short frames?
I suspect the only same approach it do disable hardware RSO.
Set the receive skb and USB buffer size to 2k.
Copy all the small frames into 'fresh' skb.
Leave any large frame with the full 'truesize'.
Although it may be necessary to completely rewrite the usbnet
code for USB3.
Instead of putting the buffers of large skb into the XHCI ring
put single USB3-sized buffers into the ring and then build
the skb out of the received data fragments.
> - ax88179_rx_checksum(ax_skb, pkt_hdr);
> + if ((pkt_hdr_val & (AX_RXHDR_CRC_ERR | AX_RXHDR_DROP_ERR)) ||
> + pkt_len < 2 + ETH_HLEN) {
> + dev->net->stats.rx_errors++;
> + skb_pull(skb, pkt_len_buf);
> + continue;
> + }
>
> - if (last)
> - return 1;
> + /* last packet */
> + if (pkt_len_buf == skb->len) {
> + skb_trim(skb, pkt_len);
>
> - usbnet_skb_return(dev, ax_skb);
> + /* Skip IP alignment pseudo header */
> + skb_pull(skb, 2);
> +
> + ax88179_rx_checksum(skb, pkt_hdr_val);
> + return 1;
> }
>
> - /* Trim this packet away from the SKB */
> - if (!skb_pull(skb, (pkt_len + 7) & 0xFFF8))
> + ax_skb = skb_clone(skb, GFP_ATOMIC);
> + if (!ax_skb)
There ought to be an error count here.
I know there wasn't one before.
David
> return 0;
> + skb_trim(ax_skb, pkt_len);
> +
> + /* Skip IP alignment pseudo header */
> + skb_pull(ax_skb, 2);
> +
> + ax88179_rx_checksum(ax_skb, pkt_hdr_val);
> + usbnet_skb_return(dev, ax_skb);
> +
> + skb_pull(skb, pkt_len_buf);
> }
> +
> + return 0;
> }
>
> static struct sk_buff *
>
> --
-
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