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Thu, 15 Oct 2026 01:20:14 -0700 (PDT) From: Andrea Parri To: Alex Williamson , Ankit Agrawal Cc: Andrea Parri , Jason Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Jiaqi Yan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2 1/2] vfio/nvgrace-gpu: Use a core-only open_device in fallback mode Date: Thu, 15 Oct 2026 10:19:34 +0200 Message-ID: <20261015081937.405320-2-parri.andrea@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261015081937.405320-1-parri.andrea@gmail.com> References: <20261015081937.405320-1-parri.andrea@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When the ACPI memory properties are missing or the C2C link is down, the device is exposed through nvgrace_gpu_pci_core_ops. That table opens through nvgrace_gpu_open_device() but closes through vfio_pci_core_close_device(), so open and close are not symmetric. nvgrace_gpu_open_device() registers nvdev->usemem for poison handling unconditionally. In fallback mode usemem.memlength is zero, and register_pfn_address_space() inserts a node covering [0, ULONG_MAX]. Nothing removes it: a second open fails with -EBUSY, and once the device is unbound the node outlives the nvdev that contains it. The next open after a rebind reports: BUG: KASAN: slab-use-after-free in interval_tree_iter_first+0x209/0x310 Read of size 8 at addr ffff88800894aa30 by task nvgrace_repro/203 Call Trace: dump_stack_lvl+0x5d/0x80 print_report+0x153/0x4c6 kasan_report+0xe4/0x1a0 interval_tree_iter_first+0x209/0x310 register_pfn_address_space+0x97/0x100 nvgrace_gpu_open_device+0x21c/0x730 vfio_df_open+0x213/0x520 vfio_df_ioctl_bind_iommufd+0x3e8/0x6e0 vfio_device_fops_unl_ioctl+0x782/0x1570 __x64_sys_ioctl+0x13c/0x1c0 do_syscall_64+0x106/0x630 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 188: ... _vfio_alloc_device+0x3a/0x500 nvgrace_gpu_probe+0xcb/0x660 local_pci_probe+0xcf/0x170 ... Freed by task 188: ... kfree+0x20d/0x600 device_release+0xcf/0x250 kobject_put+0x152/0x2f0 pci_device_remove+0xb0/0x1c0 device_release_driver_internal+0x38d/0x540 unbind_store+0xde/0x100 ... Give the fallback table its own open_device that only calls vfio_pci_core_enable() and vfio_pci_core_finish_enable(), the counterpart of vfio_pci_core_close_device(). Fallback mode then never touches the nvgrace memory regions, as Alex suggested. This should be safe because the fallback table uses the vfio-pci core read, write and mmap handlers, so nothing there uses the state nvgrace_gpu_open_device() sets up. The one visible difference is that a fallback open no longer fails when BAR0 cannot be mapped, which matches vfio-pci. Fixes: e5f19b619fa0 ("vfio/nvgrace-gpu: register device memory for poison handling") Cc: stable@vger.kernel.org Suggested-by: Alex Williamson Assisted-by: LLM Signed-off-by: Andrea Parri --- v2: Replace the usemem.memlength guards with a core-only open_device for the fallback table (Alex) Ankit confirmed fallback mode does not need the BAR0 check: https://lore.kernel.org/r/SAWPR12MB99926787B53C4FF469A6F3BE7AB09D2@SAWPR12MB999267.namprd12.prod.outlook.com/ v1: https://lore.kernel.org/r/20260925161024.189771-1-parri.andrea@gmail.com/ drivers/vfio/pci/nvgrace-gpu/main.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c index 963fd8ded20d1..208463c218088 100644 --- a/drivers/vfio/pci/nvgrace-gpu/main.c +++ b/drivers/vfio/pci/nvgrace-gpu/main.c @@ -1083,6 +1083,21 @@ static const struct vfio_device_ops nvgrace_gpu_pci_ops = { .detach_ioas = vfio_iommufd_physical_detach_ioas, }; +static int nvgrace_gpu_core_open_device(struct vfio_device *core_vdev) +{ + struct vfio_pci_core_device *vdev = + container_of(core_vdev, struct vfio_pci_core_device, vdev); + int ret; + + ret = vfio_pci_core_enable(vdev); + if (ret) + return ret; + + vfio_pci_core_finish_enable(vdev); + + return 0; +} + static const struct vfio_pci_device_ops nvgrace_gpu_pci_dev_core_ops = { .get_dmabuf_phys = vfio_pci_core_get_dmabuf_phys, }; @@ -1091,7 +1106,7 @@ static const struct vfio_device_ops nvgrace_gpu_pci_core_ops = { .name = "nvgrace-gpu-vfio-pci-core", .init = vfio_pci_core_init_dev, .release = vfio_pci_core_release_dev, - .open_device = nvgrace_gpu_open_device, + .open_device = nvgrace_gpu_core_open_device, .close_device = vfio_pci_core_close_device, .ioctl = vfio_pci_core_ioctl, .get_region_info_caps = vfio_pci_ioctl_get_region_info, -- 2.53.0