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([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48db9463499sm8727077f8f.3.2026.10.10.07.02.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 10 Oct 2026 07:02:29 -0700 (PDT) Message-ID: <12d8d2fc-6b3a-432f-b27d-e27bea01d697@gmail.com> Date: Sat, 10 Oct 2026 15:02:26 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v1 1/4] net: devmem: unmap dma_buf synchronously on queue uninstall To: Mina Almasry , Jakub Kicinski , David Wei , Taehee Yoo , Stanislav Fomichev , Paolo Abeni , Kaiyuan Zhang , Bobby Eshleman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Simon Horman , Shuah Khan , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , Daniel Borkmann , Nikolay Aleksandrov , Tariq Toukan , Kaifeng Wang References: <20261010025532.839559-1-almasrymina@google.com> <20261010025532.839559-2-almasrymina@google.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20261010025532.839559-2-almasrymina@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/10/26 03:55, Mina Almasry wrote: > When a bound net_device is unregistered while userspace still holds a > netlink or TCP socket reference on a devmem binding, > mp_dmabuf_devmem_uninstall() clears binding->dev to NULL so > netdev_nl_sock_priv_destroy() will not touch the unregistered > net_device, but leaves the dma_buf attachment mapped until > __net_devmem_dmabuf_binding_free() runs later on socket close. > > Because dma_buf_attach() does not take a reference on dma_dev, device > removal frees dma_dev while the attachment is still mapped. Closing the > netlink socket afterwards triggers a slab use-after-free in > dma_unmap_sg_attrs(): > > BUG: KASAN: slab-use-after-free in dma_unmap_sg_attrs+0x76/0x2b0 > Read of size 8 at addr ffff88810fae64b0 by task kworker/3:1/53 > Workqueue: events __net_devmem_dmabuf_binding_free > Call Trace: > dma_unmap_sg_attrs+0x76/0x2b0 > unmap_udmabuf+0x8e/0x100 > dma_buf_unmap_attachment+0x145/0x330 > dma_buf_unmap_attachment_unlocked+0x96/0x130 > __net_devmem_dmabuf_binding_free+0x156/0x2e0 > Freed by task 9: > kfree+0x1b8/0x550 > nsim_bus_dev_release+0xe/0x60 > device_release+0xcf/0x250 > > Add net_devmem_dmabuf_binding_unmap() serialized under binding->lock > and null out binding->sgt and binding->attachment after unmapping so > unmapping is idempotent across queue uninstall and deferred binding > destruction. Call it synchronously when the last bound RX queue is > uninstalled in mp_dmabuf_devmem_uninstall(). > > Fixes: f8350a4358fc ("net: page_pool: add a mp hook to unregister_netdevice*") It looks more like 170aafe35cb98e0f3fbacb446ea86389fbce22ea ("netdev: support binding dma-buf to netdevice"). The one in the tag didn't do anything interesting. The fix looks good as well, might be a good idea to clear net_iov's dma_addr as well. Reviewed-by: Pavel Begunkov -- Pavel Begunkov