From: Andy Spencer aspencer@spacex.com
[ Upstream commit 202a0a70e445caee1d0ec7aae814e64b1189fa4d ]
When the frame check sequence (FCS) is split across the last two frames of a fragmented packet, part of the FCS gets counted twice, once when subtracting the FCS, and again when subtracting the previously received data.
For example, if 1602 bytes are received, and the first fragment contains the first 1600 bytes (including the first two bytes of the FCS), and the second fragment contains the last two bytes of the FCS:
'skb->len == 1600' from the first fragment
size = lstatus & BD_LENGTH_MASK; # 1602 size -= ETH_FCS_LEN; # 1598 size -= skb->len; # -2
Since the size is unsigned, it wraps around and causes a BUG later in the packet handling, as shown below:
kernel BUG at ./include/linux/skbuff.h:2068! Oops: Exception in kernel mode, sig: 5 [#1] ... NIP [c021ec60] skb_pull+0x24/0x44 LR [c01e2fbc] gfar_clean_rx_ring+0x498/0x690 Call Trace: [df7edeb0] [c01e2c1c] gfar_clean_rx_ring+0xf8/0x690 (unreliable) [df7edf20] [c01e33a8] gfar_poll_rx_sq+0x3c/0x9c [df7edf40] [c023352c] net_rx_action+0x21c/0x274 [df7edf90] [c0329000] __do_softirq+0xd8/0x240 [df7edff0] [c000c108] call_do_irq+0x24/0x3c [c0597e90] [c00041dc] do_IRQ+0x64/0xc4 [c0597eb0] [c000d920] ret_from_except+0x0/0x18 --- interrupt: 501 at arch_cpu_idle+0x24/0x5c
Change the size to a signed integer and then trim off any part of the FCS that was received prior to the last fragment.
Fixes: 6c389fc931bc ("gianfar: fix size of scatter-gathered frames") Signed-off-by: Andy Spencer aspencer@spacex.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/net/ethernet/freescale/gianfar.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index e3b41ba95168..fa877f1e7f6f 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -2935,7 +2935,7 @@ static irqreturn_t gfar_transmit(int irq, void *grp_id) static bool gfar_add_rx_frag(struct gfar_rx_buff *rxb, u32 lstatus, struct sk_buff *skb, bool first) { - unsigned int size = lstatus & BD_LENGTH_MASK; + int size = lstatus & BD_LENGTH_MASK; struct page *page = rxb->page; bool last = !!(lstatus & BD_LFLAG(RXBD_LAST));
@@ -2950,11 +2950,16 @@ static bool gfar_add_rx_frag(struct gfar_rx_buff *rxb, u32 lstatus, if (last) size -= skb->len;
- /* in case the last fragment consisted only of the FCS */ + /* Add the last fragment if it contains something other than + * the FCS, otherwise drop it and trim off any part of the FCS + * that was already received. + */ if (size > 0) skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, rxb->page_offset + RXBUF_ALIGNMENT, size, GFAR_RXB_TRUESIZE); + else if (size < 0) + pskb_trim(skb, skb->len + size); }
/* try reuse page */