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Mon, 09 Nov 2026 11:53:04 -0800 (PST) Received: from localhost ([2a03:2880:9ff:70::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-375218c863csm447069eec.28.2026.11.09.11.53.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 11:53:04 -0800 (PST) Date: Mon, 9 Nov 2026 11:52:55 -0800 From: Stanislav Fomichev To: Mina Almasry Cc: netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Shuah Khan , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Borkmann , Nikolay Aleksandrov , David Wei , Bobby Eshleman , Dragos Tatulea Subject: Re: [PATCH net-next v2 5/6] net: devmem: resolve physical map_dev for leased RX bindings Message-ID: References: <20261108055809.2122934-1-almasrymina@google.com> <20261108055809.2122934-6-almasrymina@google.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261108055809.2122934-6-almasrymina@google.com> On 11/08, Mina Almasry wrote: > Previously, netdev_nl_bind_rx_doit() passed netdev as both map_dev and > bind_dev to net_devmem_bind_dmabuf(), so leased RX bindings stored the > virtual netdev in binding->map_dev without tracking the physical backing > netdev at all. Unregistering the physical backing netdev while a leased > RX binding was active failed to detach and unmap the dmabuf. > > Return the physical backing net_device from netdev_nl_get_dma_dev() when > the RX queue is leased from another netdev, lock map_dev around > net_devmem_bind_dmabuf() when map_dev != netdev (matching > netdev_nl_bind_tx_doit()), and assert in net_devmem_bind_dmabuf() that > both bind_dev and map_dev are locked. > > Because a leased map_dev is reached via rxq->lease->dev and locked with > raw netdev_lock(map_dev) rather than netdev_get_by_index_lock(), it may > already have entered NETREG_UNREGISTERING and completed > net_devmem_dev_unregister(map_dev) before cascaded unregistration of > bind_dev tears down the lease. Reject binding in > net_devmem_bind_dmabuf() if map_dev->reg_state != NETREG_REGISTERED. > > Signed-off-by: Mina Almasry > --- > net/core/devmem.c | 12 ++++++++++++ > net/core/netdev-genl.c | 19 ++++++++++++++++--- > 2 files changed, 28 insertions(+), 3 deletions(-) > > diff --git a/net/core/devmem.c b/net/core/devmem.c > index bb785a871d1c4..2dac581a57e13 100644 > --- a/net/core/devmem.c > +++ b/net/core/devmem.c > @@ -321,6 +321,18 @@ net_devmem_bind_dmabuf(struct net_device *map_dev, > size_t i; > long err; > > + netdev_assert_locked(bind_dev); > + netdev_assert_locked(map_dev); > + > + /* When map_dev != bind_dev, map_dev is locked via the queue lease > + * rather than netdev_get_by_index_lock(), so it may already be > + * unregistering before cascaded bind_dev unregistration runs. > + */ > + if (map_dev->reg_state != NETREG_REGISTERED) { > + NL_SET_ERR_MSG(extack, "Device is being unregistered"); > + return ERR_PTR(-ENODEV); > + } And you can call this new lease-valid here as well? Otherwise, the changes are too LLM-y, testing some super low-level conditions and are a bit hard to read/follow?