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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4900c16c744sm177738225e9.3.2026.05.19.13.35.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2026 13:35:33 -0700 (PDT) From: David Carlier To: netdev@vger.kernel.org Cc: stable@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, sdf@fomichev.me, sdf.kernel@gmail.com, kaiyuanz@google.com, almasrymina@google.com, bobbyeshleman@gmail.com, linux-kernel@vger.kernel.org, David Carlier Subject: [PATCH net v2] net: devmem: reject dma-buf bind with non-page-aligned size or SG length Date: Tue, 19 May 2026 21:35:30 +0100 Message-ID: <20260519203530.66310-1-devnexen@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" net_devmem_bind_dmabuf() trusts dmabuf->size and sg_dma_len() to be PAGE_SIZE multiples without checking: - tx_vec is sized dmabuf->size / PAGE_SIZE, and net_devmem_get_niov_at() only bounds-checks virt_addr < dmabuf->size before indexing tx_vec[virt_addr / PAGE_SIZE]. With size =3D N*PAGE_SIZE + r (1 <=3D r < PAGE_SIZE), sendmsg() at iov_base =3D N*PAGE_SIZE passes the bound check and reads tx_vec[N] -- one past. - owner->area.num_niovs =3D len / PAGE_SIZE while gen_pool_add_owner() covers the full byte len, so a non-page-multiple non-final sg desyncs num_niovs from the gen_pool region for every later sg, on both RX and TX. dma-buf does not require page-aligned sizes, so the bind path has to enforce what its own indexing assumes. Reject both with -EINVAL. The size check is TX-only (only tx_vec is sized off dmabuf->size); the SG-length check covers both directions. Fixes: bd61848900bf ("net: devmem: Implement TX path") Cc: stable@vger.kernel.org Signed-off-by: David Carlier Acked-by: Stanislav Fomichev Reviewed-by: Bobby Eshleman Reviewed-by: Mina Almasry --- Changes in v2: - Reframe commit message around the kernel-side OOB instead of "real exporters already page-align", which read as the OOB being unreachable and undercut Cc: stable (Stanislav Fomichev). - Hoist the SG-length check out of the if (TX) branch so it covers RX too; RX has the same num_niovs / gen_pool desync on a contract-violating exporter, just without an OOB. Keep the size-multiple check TX-only (Stanislav Fomichev). - Drop bool todevice; compare direction =3D=3D DMA_TO_DEVICE inline to match the existing call site at the tx_vec[] assignment (Bobby Eshleman). net/core/devmem.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/net/core/devmem.c b/net/core/devmem.c index 468344739db2..4f71de44c0fb 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -241,6 +241,11 @@ net_devmem_bind_dmabuf(struct net_device *dev, } =20 if (direction =3D=3D DMA_TO_DEVICE) { + if (!IS_ALIGNED(dmabuf->size, PAGE_SIZE)) { + err =3D -EINVAL; + NL_SET_ERR_MSG(extack, "TX dma-buf size must be a multiple of PAGE_SIZE= "); + goto err_unmap; + } binding->tx_vec =3D kvmalloc_objs(struct net_iov *, dmabuf->size / PAGE_SIZE); if (!binding->tx_vec) { @@ -267,6 +272,12 @@ net_devmem_bind_dmabuf(struct net_device *dev, size_t len =3D sg_dma_len(sg); struct net_iov *niov; =20 + if (!IS_ALIGNED(len, PAGE_SIZE)) { + err =3D -EINVAL; + NL_SET_ERR_MSG(extack, "dma-buf SG length must be PAGE_SIZE aligned"); + goto err_free_chunks; + } + owner =3D kzalloc_node(sizeof(*owner), GFP_KERNEL, dev_to_node(&dev->dev)); if (!owner) { --=20 2.53.0