On Mon, Oct 19, 2026 at 04:55:44PM +0800, Jiale Yao wrote:
> remove_id_store() can free a matching dynamic ID while VMBus is
> preparing to invoke a driver probe.
And how can that be triggered?
> Copy the ID while holding the dynamic ID lock so probe never receives
> a pointer into a freed list entry.
Why is this driver allowed to handle dynamic ids at all? Is it really
required? That will taint the kernel so no real workflow requires it,
right?
> Fixes: fc76936d3ea5 ("vmbus: add support for dynamic device id's")
No cc: stable?
> Signed-off-by: Jiale Yao <[email protected]>
> ---
> drivers/hv/vmbus_drv.c | 25 +++++++++++++++----------
> 1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 4692687cdbf3..96ad0dfaa50b 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -661,21 +661,22 @@ hv_vmbus_dev_match(const struct hv_vmbus_device_id *id,
> const guid_t *guid)
> }
>
> static const struct hv_vmbus_device_id *
> -hv_vmbus_dynid_match(struct hv_driver *drv, const guid_t *guid)
> +hv_vmbus_dynid_match(struct hv_driver *drv, const guid_t *guid,
> + struct hv_vmbus_device_id *id_copy)
> {
> - const struct hv_vmbus_device_id *id = NULL;
> struct vmbus_dynid *dynid;
>
> spin_lock(&drv->dynids.lock);
> list_for_each_entry(dynid, &drv->dynids.list, node) {
> if (guid_equal(&dynid->id.guid, guid)) {
> - id = &dynid->id;
> - break;
> + *id_copy = dynid->id;
Shouldn't this be a memcpy() as that's what you are really doing?
> + spin_unlock(&drv->dynids.lock);
guard() usage instead?
> + return id_copy;
> }
> }
> spin_unlock(&drv->dynids.lock);
>
> - return id;
> + return NULL;
> }
>
> static const struct hv_vmbus_device_id vmbus_device_null;
> @@ -685,7 +686,8 @@ static const struct hv_vmbus_device_id vmbus_device_null;
> * If there is no match, return NULL.
> */
> static const struct hv_vmbus_device_id *hv_vmbus_get_id(const struct
> hv_driver *drv,
> - struct hv_device *dev)
> + struct hv_device *dev,
> + struct
> hv_vmbus_device_id *id_copy)
> {
> const guid_t *guid = &dev->dev_type;
> const struct hv_vmbus_device_id *id;
> @@ -697,7 +699,7 @@ static const struct hv_vmbus_device_id
> *hv_vmbus_get_id(const struct hv_driver *
> return NULL;
>
> /* Look at the dynamic ids first, before the static ones */
> - id = hv_vmbus_dynid_match((struct hv_driver *)drv, guid);
> + id = hv_vmbus_dynid_match((struct hv_driver *)drv, guid, id_copy);
> if (!id)
> id = hv_vmbus_dev_match(drv->id_table, guid);
>
> @@ -773,6 +775,7 @@ static ssize_t new_id_store(struct device_driver *driver,
> const char *buf,
> size_t count)
> {
> struct hv_driver *drv = drv_to_hv_drv(driver);
> + struct hv_vmbus_device_id id_copy;
On the stack?
Ok, I guess this would work, but it feels clunky, why doesn't all other
busses have to do this too?
thanks,
greg k-h
