RE: [PATCH v3 1/2] Drivers: hv: vmbus: prevent duplicate dynamic IDs
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From: Michael Kelley <hidden>
Date: 2026-10-27 17:09:04
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lkml, stable
From: Jiale Yao <redacted> Sent: Monday, October 26, 2026 11:57 PM
new_id_store() checks for an existing dynamic ID before calling
vmbus_add_dynid(), but the check and insertion use separate critical
sections. Two concurrent writers can therefore both observe that a GUID is
absent and add duplicate entries. Removing the GUID once then leaves the
duplicate active.
Move the duplicate check into vmbus_add_dynid() so it is performed under
the same lock as the list insertion.
Fixes: fc76936d3ea5 ("vmbus: add support for dynamic device id's")
Cc: <redacted>
Tested-by: Kameron Carr <redacted>
Reviewed-by: Kameron Carr <redacted>
Signed-off-by: Jiale Yao <redacted>Reviewed-by: Michael Kelley <redacted>
quoted hunk ↗ jump to hunk
--- drivers/hv/vmbus_drv.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 4692687cdbf3..1037117e2d81 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c@@ -737,7 +737,7 @@ static const struct hv_vmbus_device_id *hv_vmbus_get_id(const struct hv_driver * */ static int vmbus_add_dynid(struct hv_driver *drv, guid_t *guid) { - struct vmbus_dynid *dynid; + struct vmbus_dynid *dynid, *existing; dynid = kzalloc_obj(*dynid); if (!dynid)@@ -745,9 +745,16 @@ static int vmbus_add_dynid(struct hv_driver *drv, guid_t *guid) dynid->id.guid = *guid; - spin_lock(&drv->dynids.lock); - list_add_tail(&dynid->node, &drv->dynids.list); - spin_unlock(&drv->dynids.lock); + scoped_guard(spinlock, &drv->dynids.lock) { + list_for_each_entry(existing, &drv->dynids.list, node) { + if (guid_equal(&existing->id.guid, guid)) { + kfree(dynid); + return -EEXIST; + } + } + + list_add_tail(&dynid->node, &drv->dynids.list); + } return driver_attach(&drv->driver); }@@ -780,9 +787,6 @@ static ssize_t new_id_store(struct device_driver *driver, const char *buf, if (retval) return retval; - if (hv_vmbus_dynid_match(drv, &guid)) - return -EEXIST; - retval = vmbus_add_dynid(drv, &guid); if (retval) return retval; --2.34.1