From: Jacob Pan Date: Wed, 18 Jun 2025 23:46:18 +0000 (-0700) Subject: vfio: Prevent open_count decrement to negative X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=982ddd59ed97dc7e63efd97ed50273ffb817bd41;p=thirdparty%2Flinux.git vfio: Prevent open_count decrement to negative When vfio_df_close() is called with open_count=0, it triggers a warning in vfio_assert_device_open() but still decrements open_count to -1. This allows a subsequent open to incorrectly pass the open_count == 0 check, leading to unintended behavior, such as setting df->access_granted = true. For example, running an IOMMUFD compat no-IOMMU device with VFIO tests (https://github.com/awilliam/tests/blob/master/vfio-noiommu-pci-device-open.c) results in a warning and a failed VFIO_GROUP_GET_DEVICE_FD ioctl on the first run, but the second run succeeds incorrectly. Add checks to avoid decrementing open_count below zero. Fixes: 05f37e1c03b6 ("vfio: Pass struct vfio_device_file * to vfio_device_open/close()") Reviewed-by: Jason Gunthorpe Reviewed-by: Yi Liu Signed-off-by: Jacob Pan Link: https://lore.kernel.org/r/20250618234618.1910456-2-jacob.pan@linux.microsoft.com Signed-off-by: Alex Williamson --- diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 1fd261efc582..5046cae05222 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -583,7 +583,8 @@ void vfio_df_close(struct vfio_device_file *df) lockdep_assert_held(&device->dev_set->lock); - vfio_assert_device_open(device); + if (!vfio_assert_device_open(device)) + return; if (device->open_count == 1) vfio_df_device_last_close(df); device->open_count--;