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Miller" , Eric Dumazet , Jesper Dangaard Brouer , Ilias Apalodimas , Simon Horman , Shuah Khan , Sumit Semwal , Christian =?utf-8?B?S8O2bmln?= , Dragos Tatulea , Nikolay Aleksandrov , Daniel Borkmann , Tariq Toukan , Kaifeng Wang Subject: Re: [PATCH net v4 2/4] net: devmem: detach TX bindings on NETDEV_UNREGISTER Message-ID: References: <20261015163915.1166043-1-almasrymina@google.com> <20261015163915.1166043-3-almasrymina@google.com> Precedence: bulk X-Mailing-List: netdev@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: <20261015163915.1166043-3-almasrymina@google.com> On 10/15, Mina Almasry wrote: > TX devmem bindings (NETDEV_CMD_BIND_TX) have no bound RX queues, so > mp_dmabuf_devmem_uninstall() never runs when binding->dev or > binding->vdev unregisters. As a result, binding->dev and binding->vdev > dangle pointing to freed struct net_device memory, and the dma_buf > remains attached and mapped after device removal. > > Closing the netlink socket after netdev unregistration dereferences the > freed struct net_device in netdev_nl_sock_priv_destroy(): > > BUG: unable to handle page fault for address: ffff88824ca9b000 > Oops: Oops: 0000 [#1] SMP KASAN NOPTI > RIP: 0010:netdev_nl_sock_priv_destroy+0xbd/0x1e0 > Call Trace: > genl_release+0xf5/0x190 > netlink_release+0xd01/0x18d0 > __sock_release+0xb0/0x270 > sock_close+0x18/0x20 > > Extend net_devmem_dev_unregister() to TX bindings, including ones > whose netlink socket is already closed but which TCP retransmits keep > alive: > - When binding->dev (the physical DMA-capable device) unregisters, > clear the binding's NET_DEVMEM_BINDING_LIVE mark and both > binding->dev and binding->vdev, and unmap the dma_buf under > binding->lock. No grace period is needed: the device is already > closed, so nothing hands the DMA addresses to the hardware anymore, > and concurrent senders only compare against binding->dev. > - When only binding->vdev (virtual device) unregisters while > binding->dev lives, only clear binding->vdev so no new TX sends match > the virtual device while allowing in-flight TX packets on binding->dev > to finish DMA safely. > > Fixes: bd61848900bf ("net: devmem: Implement TX path") > Fixes: 1abe839b34ae ("net: devmem: support TX over NETMEM_TX_NO_DMA devices") > Suggested-by: Stanislav Fomichev > Cc: Kaiyuan Zhang > Cc: Bobby Eshleman > Cc: Tariq Toukan > Cc: Kaifeng Wang > Assisted-by: LLM > Signed-off-by: Mina Almasry > Reviewed-by: Dragos Tatulea > --- > v4: > - Detach and unmap TX bindings directly from the xarray walk, without a > grace period or a second pass (Stanislav). Acked-by: Stanislav Fomichev