net: macb: fix random memory corruption on RX with 64-bit DMA

[ Upstream commit e100a897bf9b19089e57f236f2398c9e0538900e ]

64-bit DMA addresses are split in upper and lower halves that are
written in separate fields on GEM. For RX, bit 0 of the address is used
as the ownership bit (RX_USED). When the RX_USED bit is unset the
controller is allowed to write data to the buffer.

The driver does not guarantee that the controller already sees the upper
half when the RX_USED bit is cleared, possibly resulting in the
controller writing an incoming frame to an address with an incorrect
upper half and therefore possibly corrupting unrelated system memory.

Fix that by adding the necessary DMA memory barrier between the writes.

This corruption was observed on a ZynqMP based system.

Fixes: fff8019a08b6 ("net: macb: Add 64 bit addressing support for GEM")
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Acked-by: Harini Katakam <harini.katakam@xilinx.com>
Tested-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 0b2f9ddfb1c446d4661ef86b95d5a6f6424a6dd8..3aabc36eec0bfd77259bfe771509b9e7136378e6 100644 (file)
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -675,6 +675,11 @@ static void macb_set_addr(struct macb *bp, struct macb_dma_desc *desc, dma_addr_
        if (bp->hw_dma_cap & HW_DMA_CAP_64B) {
                desc_64 = macb_64b_desc(bp, desc);
                desc_64->addrh = upper_32_bits(addr);
+               /* The low bits of RX address contain the RX_USED bit, clearing
+                * of which allows packet RX. Make sure the high bits are also
+                * visible to HW at that point.
+                */
+               dma_wmb();
        }
 #endif
        desc->addr = lower_32_bits(addr);