From 1bd24b0e16cc01d0c11f6eea8c78683f38ab13bc Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Wed, 15 Jan 2020 13:53:45 +0200 Subject: [PATCH] mlxsw: spectrum: Do not modify cloned SKBs during xmit The driver needs to prepend a Tx header to each packet it is transmitting. The header includes information such as the egress port and traffic class. The addition of the header requires the driver to modify the SKB's header and therefore it must not be shared. Otherwise, we risk hitting various race conditions. For example, when a packet is flooded (cloned) by the bridge driver to two switch ports swp1 and swp2: t0 - mlxsw_sp_port_xmit() is called for swp1. Tx header is prepended with swp1's port number t1 - mlxsw_sp_port_xmit() is called for swp2. Tx header is prepended with swp2's port number, overwriting swp1's port number t2 - The device processes data buffer from t0. Packet is transmitted via swp2 t3 - The device processes data buffer from t1. Packet is transmitted via swp2 Usually, the device is fast enough and transmits the packet before its Tx header is overwritten, but this is not the case in emulated environments. Fix this by making sure the SKB's header is writable by calling skb_cow_head(). Since the function ensures we have headroom to push the Tx header, the check further in the function can be removed. v2: * Use skb_cow_head() instead of skb_unshare() as suggested by Jakub * Remove unnecessary check regarding headroom Fixes: a3f159160767 ("mlxsw: spectrum: Add initial support for Spectrum ASIC") Signed-off-by: Ido Schimmel Reported-by: Shalom Toledo Acked-by: Jiri Pirko Signed-off-by: David S. Miller --- drivers/net/ethernet/mellanox/mlxsw/spectrum.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c index 5408a964bd105..2394c425b47dd 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c @@ -860,23 +860,17 @@ static netdev_tx_t mlxsw_sp_port_xmit(struct sk_buff *skb, u64 len; int err; + if (skb_cow_head(skb, MLXSW_TXHDR_LEN)) { + this_cpu_inc(mlxsw_sp_port->pcpu_stats->tx_dropped); + dev_kfree_skb_any(skb); + return NETDEV_TX_OK; + } + memset(skb->cb, 0, sizeof(struct mlxsw_skb_cb)); if (mlxsw_core_skb_transmit_busy(mlxsw_sp->core, &tx_info)) return NETDEV_TX_BUSY; - if (unlikely(skb_headroom(skb) < MLXSW_TXHDR_LEN)) { - struct sk_buff *skb_orig = skb; - - skb = skb_realloc_headroom(skb, MLXSW_TXHDR_LEN); - if (!skb) { - this_cpu_inc(mlxsw_sp_port->pcpu_stats->tx_dropped); - dev_kfree_skb_any(skb_orig); - return NETDEV_TX_OK; - } - dev_consume_skb_any(skb_orig); - } - if (eth_skb_pad(skb)) { this_cpu_inc(mlxsw_sp_port->pcpu_stats->tx_dropped); return NETDEV_TX_OK; -- 2.39.5