net: stmmac: fix TSO DMA API usage causing oops

JIRA: https://issues.redhat.com/browse/RHEL-84762

commit 4c49f38
Author: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Date:   Fri Dec 6 12:40:11 2024 +0000

    net: stmmac: fix TSO DMA API usage causing oops

    Commit 66600fa ("net: stmmac: TSO: Fix unbalanced DMA map/unmap
    for non-paged SKB data") moved the assignment of tx_skbuff_dma[]'s
    members to be later in stmmac_tso_xmit().

    The buf (dma cookie) and len stored in this structure are passed to
    dma_unmap_single() by stmmac_tx_clean(). The DMA API requires that
    the dma cookie passed to dma_unmap_single() is the same as the value
    returned from dma_map_single(). However, by moving the assignment
    later, this is not the case when priv->dma_cap.addr64 > 32 as "des"
    is offset by proto_hdr_len.

    This causes problems such as:

      dwc-eth-dwmac 2490000.ethernet eth0: Tx DMA map failed

    and with DMA_API_DEBUG enabled:

      DMA-API: dwc-eth-dwmac 2490000.ethernet: device driver tries to +free DMA memory it has not allocated [device address=0x000000ffffcf65c0] [size=66 bytes]

    Fix this by maintaining "des" as the original DMA cookie, and use
    tso_des to pass the offset DMA cookie to stmmac_tso_allocator().

    Full details of the crashes can be found at:
    https://lore.kernel.org/all/d8112193-0386-4e14-b516-37c2d838171a@nvidia.com/
    https://lore.kernel.org/all/klkzp5yn5kq5efgtrow6wbvnc46bcqfxs65nz3qy77ujr5turc@bwwhelz2l4dw/

    Reported-by: Jon Hunter <jonathanh@nvidia.com>
    Reported-by: Thierry Reding <thierry.reding@gmail.com>
    Fixes: 66600fa ("net: stmmac: TSO: Fix unbalanced DMA map/unmap for non-paged SKB data")
    Tested-by: Jon Hunter <jonathanh@nvidia.com>
    Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
    Reviewed-by: Furong Xu <0x1207@gmail.com>
    Link: https://patch.msgid.link/E1tJXcx-006N4Z-PC@rmk-PC.armlinux.org.uk
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Izabela Bakollari <ibakolla@redhat.com>

Author: Izabela Bakollari

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -4217,8 +4217,8 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct stmmac_txq_stats *txq_stats;
 	struct stmmac_tx_queue *tx_q;
 	u32 pay_len, mss, queue;
+	dma_addr_t tso_des, des;
 	u8 proto_hdr_len, hdr;
-	dma_addr_t des;
 	bool set_ic;
 	int i;
 
@@ -4314,14 +4314,15 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		/* If needed take extra descriptors to fill the remaining payload */
 		tmp_pay_len = pay_len - TSO_MAX_BUFF_SIZE;
+		tso_des = des;
 	} else {
 		stmmac_set_desc_addr(priv, first, des);
 		tmp_pay_len = pay_len;
-		des += proto_hdr_len;
+		tso_des = des + proto_hdr_len;
 		pay_len = 0;
 	}
 
-	stmmac_tso_allocator(priv, des, tmp_pay_len, (nfrags == 0), queue);
+	stmmac_tso_allocator(priv, tso_des, tmp_pay_len, (nfrags == 0), queue);
 
 	/* In case two or more DMA transmit descriptors are allocated for this
 	 * non-paged SKB data, the DMA buffer address should be saved to