6.15-stable review patch. If anyone has any objections, please let me know.
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From: Jacob Pan jacob.pan@linux.microsoft.com
[ Upstream commit 982ddd59ed97dc7e63efd97ed50273ffb817bd41 ]
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 jgg@nvidia.com Reviewed-by: Yi Liu yi.l.liu@intel.com Signed-off-by: Jacob Pan jacob.pan@linux.microsoft.com Link: https://lore.kernel.org/r/20250618234618.1910456-2-jacob.pan@linux.microsoft... Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/vfio_main.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
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--;