net: stmmac: fix TSO DMA API usage causing oops

net: stmmac: fix TSO DMA API usage causing oops

Commit 66600fac7a98 ("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: 66600fac7a98 ("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>