4.4-stable review patch. If anyone has any objections, please let me know.
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From: Brian King brking@linux.vnet.ibm.com
commit 0a9a17e3bb4564caf4bfe2a6783ae1287667d188 upstream.
This patch fixes an issue seen on Power systems with ixgbe which results in skb list corruption and an eventual kernel oops. The following is what was observed:
CPU 1 CPU2 ============================ ============================ 1: ixgbe_xmit_frame_ring ixgbe_clean_tx_irq 2: first->skb = skb eop_desc = tx_buffer->next_to_watch 3: ixgbe_tx_map read_barrier_depends() 4: wmb check adapter written status bit 5: first->next_to_watch = tx_desc napi_consume_skb(tx_buffer->skb ..); 6: writel(i, tx_ring->tail);
The read_barrier_depends is insufficient to ensure that tx_buffer->skb does not get loaded prior to tx_buffer->next_to_watch, which then results in loading a stale skb pointer. This patch replaces the read_barrier_depends with smp_rmb to ensure loads are ordered with respect to the load of tx_buffer->next_to_watch.
Signed-off-by: Brian King brking@linux.vnet.ibm.com Acked-by: Jesse Brandeburg jesse.brandeburg@intel.com Tested-by: Andrew Bowers andrewx.bowers@intel.com Signed-off-by: Jeff Kirsher jeffrey.t.kirsher@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -1114,7 +1114,7 @@ static bool ixgbe_clean_tx_irq(struct ix break;
/* prevent any other reads prior to eop_desc */ - read_barrier_depends(); + smp_rmb();
/* if DD is not set pending work has not been completed */ if (!(eop_desc->wb.status & cpu_to_le32(IXGBE_TXD_STAT_DD)))