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AJvYcCU2dOohAT0EoCI+0796T/XZYx1ylxd1Z5szd0/Pm5rnY5cphLEps/tt+Sg1Io1dtRMKvPfezwFC8clalbg=@vger.kernel.org X-Gm-Message-State: AOJu0YxQsbWT/C2qSqFQUVWAewgwL923JHRGORgzAuLLjzt1Y39eVzS3 GPSGERHWfesQpNletlo05YHOnbsV6/0LMvi8rrpEFi2SbknasvmDHD+gikqzRt+P0T/4ukacmxL Gyw== X-Received: from pfgs39.prod.google.com ([2002:a05:6a00:17a7:b0:82a:108d:4308]) (user=linkl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:c92:b0:82c:d6d3:3197 with SMTP id d2e1a72fcca58-82d0daadb73mr18952159b3a.23.1775597133722; Tue, 07 Apr 2026 14:25:33 -0700 (PDT) Date: Tue, 7 Apr 2026 14:25:21 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.53.0.1213.gd9a14994de-goog Message-ID: <20260407212521.934620-1-linkl@google.com> Subject: [RFC PATCH v1] virtio_pci: only store successfully populated virtio_pci_vq_info From: Link Lin To: mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com Cc: eperezma@redhat.com, jiaqiyan@google.com, rientjes@google.com, weixugc@google.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Link Lin Content-Type: text/plain; charset="UTF-8" In environments where free page reporting is disabled, a kernel panic is triggered when tearing down the virtio_balloon module: [12261.808190] Call trace: [12261.808471] __list_del_entry_valid_or_report+0x18/0xe0 [12261.809064] vp_del_vqs+0x12c/0x270 [12261.809462] remove_common+0x80/0x98 [virtio_balloon] [12261.810034] virtballoon_remove+0xfc/0x158 [virtio_balloon] [12261.810663] virtio_dev_remove+0x68/0xf8 [12261.811108] device_release_driver_internal+0x17c/0x278 [12261.811701] driver_detach+0xd4/0x138 [12261.812117] bus_remove_driver+0x90/0xd0 [12261.812562] driver_unregister+0x40/0x70 [12261.813006] unregister_virtio_driver+0x20/0x38 [12261.813518] cleanup_module+0x20/0x7a8 [virtio_balloon] [12261.814109] __arm64_sys_delete_module+0x278/0x3d0 [12261.814654] invoke_syscall+0x5c/0x120 [12261.815086] el0_svc_common+0x90/0xf8 [12261.815506] do_el0_svc+0x2c/0x48 [12261.815883] el0_svc+0x3c/0xa8 [12261.816235] el0t_64_sync_handler+0x8c/0x108 [12261.816724] el0t_64_sync+0x198/0x1a0 The issue originates in vp_find_vqs_intx(). It kzalloc_objs() based on the nvqs count provided by the caller, virtio_balloon::init_vqs(). However, it is not always the case that all nvqs number of virtio_pci_vq_info objects will be properly populated. For example, when VIRTIO_BALLOON_F_FREE_PAGE_HINT is absent, the VIRTIO_BALLOON_VQ_FREE_PAGE-th item in the vp_dev->vqs array is actually never populated, and is still a zeroe-initialized virtio_pci_vq_info object, which is eventually going to trigger a __list_del_entry_valid_or_report() crash. Tested by applying this patch to a guest VM kernel with the VIRTIO_BALLOON_F_REPORTING feature enabled and the VIRTIO_BALLOON_F_FREE_PAGE_HINT feature disabled. Without this patch, unloading the virtio_balloon module triggers a panic. With this patch, no panic is observed. The fix is to use queue_idx to handle the case that vp_find_vqs_intx() skips vp_setup_vq() when caller provided null vqs_info[i].name, when the caller doesn't populate all nvqs number of virtqueue_info objects. Invariantly queue_idx is the correct index to store a successfully created and populated virtio_pci_vq_info object. As a result, now a virtio_pci_device object only stores queue_idx number of valid virtio_pci_vq_info objects in its vqs array when the for-loop over nvqs finishes (of course, without goto out_del_vqs). vp_find_vqs_msix() has similar issue, so fix it in the same way. This patch is marked as RFC because we are uncertain if any virtio-pci code implicitly requires virtio_pci_device's vqs array to always contain nvqs number of virtio_pci_vq_info objects, and to store zero-initialized virtio_pci_vq_info objects. We have not observed any issues in our testing, but insights or alternatives are welcome! Signed-off-by: Link Lin Co-developed-by: Jiaqi Yan Signed-off-by: Jiaqi Yan --- drivers/virtio/virtio_pci_common.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c index da97b6a988de..9b32301529e5 100644 --- a/drivers/virtio/virtio_pci_common.c +++ b/drivers/virtio/virtio_pci_common.c @@ -423,14 +423,15 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned int nvqs, vqs[i] = NULL; continue; } - vqs[i] = vp_find_one_vq_msix(vdev, queue_idx++, vqi->callback, + vqs[i] = vp_find_one_vq_msix(vdev, queue_idx, vqi->callback, vqi->name, vqi->ctx, false, &allocated_vectors, vector_policy, - &vp_dev->vqs[i]); + &vp_dev->vqs[queue_idx]); if (IS_ERR(vqs[i])) { err = PTR_ERR(vqs[i]); goto error_find; } + ++queue_idx; } if (!avq_num) @@ -485,13 +486,14 @@ static int vp_find_vqs_intx(struct virtio_device *vdev, unsigned int nvqs, vqs[i] = NULL; continue; } - vqs[i] = vp_setup_vq(vdev, queue_idx++, vqi->callback, + vqs[i] = vp_setup_vq(vdev, queue_idx, vqi->callback, vqi->name, vqi->ctx, - VIRTIO_MSI_NO_VECTOR, &vp_dev->vqs[i]); + VIRTIO_MSI_NO_VECTOR, &vp_dev->vqs[queue_idx]); if (IS_ERR(vqs[i])) { err = PTR_ERR(vqs[i]); goto out_del_vqs; } + ++queue_idx; } if (!avq_num) -- 2.53.0.1213.gd9a14994de-goog