From dc7fe87de492ea7f33a72b78d26650b75bf37f4f Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Mon, 15 Jun 2026 14:47:00 -0600 Subject: [PATCH] vfio: Remove device debugfs before releasing devres VFIO device debugfs files created with debugfs_create_devm_seqfile() store a devres allocated debugfs_devm_entry as inode private data. vfio_unregister_group_dev() currently calls vfio_device_del() before vfio_device_debugfs_exit(), but device_del() releases devres. This can leave debugfs entries visible with stale inode private data while unregister waits for userspace references to drain. Remove the per-device debugfs tree before vfio_device_del(). The debugfs view is diagnostic only, so losing it at the start of unregister is preferable to preserving entries whose backing storage may already have been released. Complete the teardown by clearing the per-device debugfs root after removal. This matches the global debugfs root cleanup and prevents future users from mistaking a removed dentry for a live debugfs tree during the remainder of unregister. Fixes: 2202844e4468 ("vfio/migration: Add debugfs to live migration driver") Reported-by: Sashiko AI Review Link: https://lore.kernel.org/r/20260615192725.6A2221F000E9@smtp.kernel.org Cc: stable@vger.kernel.org Cc: Longfang Liu Assisted-by: OpenAI Codex:gpt-5 Signed-off-by: Alex Williamson Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20260615204717.735302-1-alex.williamson@nvidia.com Signed-off-by: Alex Williamson --- drivers/vfio/debugfs.c | 1 + drivers/vfio/vfio_main.c | 8 +++++++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/debugfs.c b/drivers/vfio/debugfs.c index 8b0ca7a09064..8a2f1b0cce3f 100644 --- a/drivers/vfio/debugfs.c +++ b/drivers/vfio/debugfs.c @@ -97,6 +97,7 @@ void vfio_device_debugfs_init(struct vfio_device *vdev) void vfio_device_debugfs_exit(struct vfio_device *vdev) { debugfs_remove_recursive(vdev->debug_root); + vdev->debug_root = NULL; } void vfio_debugfs_create_root(void) diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 5e0422014523..ed538aebb0b8 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -406,6 +406,13 @@ void vfio_unregister_group_dev(struct vfio_device *device) */ vfio_device_group_unregister(device); + /* + * Remove debugfs before device_del(), which releases devres. Some + * debugfs entries are created with debugfs_create_devm_seqfile() and + * therefore rely on devres-managed inode private data. + */ + vfio_device_debugfs_exit(device); + /* * Balances vfio_device_add() in register path, also prevents * new device opened by userspace in the cdev path. @@ -435,7 +442,6 @@ void vfio_unregister_group_dev(struct vfio_device *device) } } - vfio_device_debugfs_exit(device); /* Balances vfio_device_set_group in register path */ vfio_device_remove_group(device); }