Re: [PATCH net-next 3/3] net: devmem: decode DMA addresses for TX

[Mina Almasry]

On Tue, Sep 22, 2026 at 1:43 PM Stanislav Fomichev <sdf.kernel@xxxxxxxxx> wrote:
>
> On 32-bit architectures where dma_addr_t is wider than unsigned long,
> page_pool_set_dma_addr_netmem() stores page-aligned DMA addresses shifted
> by PAGE_SHIFT. The net_iov branch of __skb_frag_dma_map() adds byte offsets
> to the encoded value, so the NIC is programmed with an invalid DMA address.
> This can trigger an IOMMU fault or DMA from unintended memory.
>
> Consolidate DMA address encoding, decoding, and representability checks in
> netmem helpers. Use the common decoder from the page pool and net_iov TX
> paths so both interpret stored addresses consistently.
>
> Fixes: bd61848900bf ("net: devmem: Implement TX path")
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxxx>

Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx>

-- 
Thanks,
Mina