From d821a4c4d11ad160925dab2bb009b8444beff484 Mon Sep 17 00:00:00 2001 From: Bruce Allan Date: Fri, 24 Aug 2012 20:38:11 +0000 Subject: [PATCH] e1000e: DoS while TSO enabled caused by link partner with small MSS With a low enough MSS on the link partner and TSO enabled locally, the networking stack can periodically send a very large (e.g. 64KB) TCP message for which the driver will attempt to use more Tx descriptors than are available by default in the Tx ring. This is due to a workaround in the code that imposes a limit of only 4 MSS-sized segments per descriptor which appears to be a carry-over from the older e1000 driver and may be applicable only to some older PCI or PCIx parts which are not supported in e1000e. When the driver gets a message that is too large to fit across the configured number of Tx descriptors, it stops the upper stack from queueing any more and gets stuck in this state. After a timeout, the upper stack assumes the adapter is hung and calls the driver to reset it. Remove the unnecessary limitation of using up to only 4 MSS-sized segments per Tx descriptor, and put in a hard failure test to catch when attempting to check for message sizes larger than would fit in the whole Tx ring. Refactor the remaining logic that limits the size of data per Tx descriptor from a seemingly arbitrary 8KB to a limit based on the dynamic size of the Tx packet buffer as described in the hardware specification. Also, fix the logic in the check for space in the Tx ring for the next largest possible packet after the current one has been successfully queued for transmit, and use the appropriate defines for default ring sizes in e1000_probe instead of magic values. This issue goes back to the introduction of e1000e in 2.6.24 when it was split off from e1000. Reported-by: Ben Hutchings Signed-off-by: Bruce Allan Cc: Stable [2.6.24+] Tested-by: Aaron Brown Signed-off-by: Jeff Kirsher Signed-off-by: David S. Miller --- drivers/net/ethernet/intel/e1000e/e1000.h | 1 + drivers/net/ethernet/intel/e1000e/netdev.c | 48 +++++++++++----------- 2 files changed, 24 insertions(+), 25 deletions(-) diff --git a/drivers/net/ethernet/intel/e1000e/e1000.h b/drivers/net/ethernet/intel/e1000e/e1000.h index cd153326c3cf..cb3356c9af80 100644 --- a/drivers/net/ethernet/intel/e1000e/e1000.h +++ b/drivers/net/ethernet/intel/e1000e/e1000.h @@ -310,6 +310,7 @@ struct e1000_adapter { */ struct e1000_ring *tx_ring /* One per active queue */ ____cacheline_aligned_in_smp; + u32 tx_fifo_limit; struct napi_struct napi; diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c index 46c3b1f9ff89..d01a099475a1 100644 --- a/drivers/net/ethernet/intel/e1000e/netdev.c +++ b/drivers/net/ethernet/intel/e1000e/netdev.c @@ -3516,6 +3516,15 @@ void e1000e_reset(struct e1000_adapter *adapter) break; } + /* + * Alignment of Tx data is on an arbitrary byte boundary with the + * maximum size per Tx descriptor limited only to the transmit + * allocation of the packet buffer minus 96 bytes with an upper + * limit of 24KB due to receive synchronization limitations. + */ + adapter->tx_fifo_limit = min_t(u32, ((er32(PBA) >> 16) << 10) - 96, + 24 << 10); + /* * Disable Adaptive Interrupt Moderation if 2 full packets cannot * fit in receive buffer. @@ -4785,12 +4794,9 @@ static bool e1000_tx_csum(struct e1000_ring *tx_ring, struct sk_buff *skb) return 1; } -#define E1000_MAX_PER_TXD 8192 -#define E1000_MAX_TXD_PWR 12 - static int e1000_tx_map(struct e1000_ring *tx_ring, struct sk_buff *skb, unsigned int first, unsigned int max_per_txd, - unsigned int nr_frags, unsigned int mss) + unsigned int nr_frags) { struct e1000_adapter *adapter = tx_ring->adapter; struct pci_dev *pdev = adapter->pdev; @@ -5023,20 +5029,19 @@ static int __e1000_maybe_stop_tx(struct e1000_ring *tx_ring, int size) static int e1000_maybe_stop_tx(struct e1000_ring *tx_ring, int size) { + BUG_ON(size > tx_ring->count); + if (e1000_desc_unused(tx_ring) >= size) return 0; return __e1000_maybe_stop_tx(tx_ring, size); } -#define TXD_USE_COUNT(S, X) (((S) >> (X)) + 1) static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev) { struct e1000_adapter *adapter = netdev_priv(netdev); struct e1000_ring *tx_ring = adapter->tx_ring; unsigned int first; - unsigned int max_per_txd = E1000_MAX_PER_TXD; - unsigned int max_txd_pwr = E1000_MAX_TXD_PWR; unsigned int tx_flags = 0; unsigned int len = skb_headlen(skb); unsigned int nr_frags; @@ -5056,18 +5061,8 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, } mss = skb_shinfo(skb)->gso_size; - /* - * The controller does a simple calculation to - * make sure there is enough room in the FIFO before - * initiating the DMA for each buffer. The calc is: - * 4 = ceil(buffer len/mss). To make sure we don't - * overrun the FIFO, adjust the max buffer len if mss - * drops. - */ if (mss) { u8 hdr_len; - max_per_txd = min(mss << 2, max_per_txd); - max_txd_pwr = fls(max_per_txd) - 1; /* * TSO Workaround for 82571/2/3 Controllers -- if skb->data @@ -5097,12 +5092,12 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, count++; count++; - count += TXD_USE_COUNT(len, max_txd_pwr); + count += DIV_ROUND_UP(len, adapter->tx_fifo_limit); nr_frags = skb_shinfo(skb)->nr_frags; for (f = 0; f < nr_frags; f++) - count += TXD_USE_COUNT(skb_frag_size(&skb_shinfo(skb)->frags[f]), - max_txd_pwr); + count += DIV_ROUND_UP(skb_frag_size(&skb_shinfo(skb)->frags[f]), + adapter->tx_fifo_limit); if (adapter->hw.mac.tx_pkt_filtering) e1000_transfer_dhcp_info(adapter, skb); @@ -5144,15 +5139,18 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, tx_flags |= E1000_TX_FLAGS_NO_FCS; /* if count is 0 then mapping error has occurred */ - count = e1000_tx_map(tx_ring, skb, first, max_per_txd, nr_frags, mss); + count = e1000_tx_map(tx_ring, skb, first, adapter->tx_fifo_limit, + nr_frags); if (count) { skb_tx_timestamp(skb); netdev_sent_queue(netdev, skb->len); e1000_tx_queue(tx_ring, tx_flags, count); /* Make sure there is space in the ring for the next send. */ - e1000_maybe_stop_tx(tx_ring, MAX_SKB_FRAGS + 2); - + e1000_maybe_stop_tx(tx_ring, + (MAX_SKB_FRAGS * + DIV_ROUND_UP(PAGE_SIZE, + adapter->tx_fifo_limit) + 2)); } else { dev_kfree_skb_any(skb); tx_ring->buffer_info[first].time_stamp = 0; @@ -6327,8 +6325,8 @@ static int __devinit e1000_probe(struct pci_dev *pdev, adapter->hw.phy.autoneg_advertised = 0x2f; /* ring size defaults */ - adapter->rx_ring->count = 256; - adapter->tx_ring->count = 256; + adapter->rx_ring->count = E1000_DEFAULT_RXD; + adapter->tx_ring->count = E1000_DEFAULT_TXD; /* * Initial Wake on LAN setting - If APM wake is enabled in