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Tue, 29 Sep 2026 09:12:46 -0700 (PDT) Date: Tue, 29 Sep 2026 08:55:31 -0700 From: Stanislav Fomichev To: Paolo Abeni Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, horms@kernel.org, hawk@kernel.org, ilias.apalodimas@linaro.org, sdf@fomichev.me, bobbyeshleman@meta.com, almasrymina@google.com, kaiyuanz@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2 3/3] net: devmem: decode DMA addresses for TX Message-ID: References: <20260925201522.254717-1-sdf@fomichev.me> <20260925201522.254717-4-sdf@fomichev.me> <85ddcc36-7e31-42d7-8e78-a3e456e13944@redhat.com> <97f2fdff-3954-4d53-aa55-156672658ee5@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <97f2fdff-3954-4d53-aa55-156672658ee5@redhat.com> 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 > > > Signed-off-by: Stanislav Fomichev > > 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!