Re: [PATCH net-next v2 3/3] net: devmem: decode DMA addresses for TX

[Stanislav Fomichev]

On 09/29, Paolo Abeni wrote:
> On 9/29/26 11:43, Paolo Abeni wrote:
> > On 9/25/26 22:15, Stanislav Fomichev 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")
> > > Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx>
> > > Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxxx>
> > Fixes tag for net-next patches pointing to old code are highly discouraged.
> > My understanding is that netem on 32 bits is mostly a theoretical thing,
> > i.e. no actual usage.
> > Would you be ok to strip the tag? No need to repost, just reply here.
> Actually the above is more FYI than a real request. I'll apply the
> series stripping the tag.

Yes, agreed, this does not look like a real issue to me either. Thanks!