In the Linux kernel, the following vulnerability has been resolved: Bluetooth: mgmt: fix 'hdev->discovery.uuids' NULL dereference 'uuid_count' membe...

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: mgmt: fix 'hdev->discovery.uuids' NULL dereference 'uuid_count' member of struct 'discovery_state' is assigned and read without any locks, so there is a chance of situation when uuid_count != 0, but uuids is NULL and there will be NULL pointer dereference. Possible race: 'hci_update_passive_scan_sync' 'hci_discovery_filter_clear' hdev->discovery.uuid_count = 0; <----------------------preempted-----------------------------> 'start_service_discovery' // Set uuid_count to value != 0 hdev->discovery.uuid_count = uuid_count; hdev->discovery.uuids = kmemdup(...); <----------------------preempted-----------------------------> spin_lock(&hdev->discovery.lock); kfree(hdev->discovery.uuids); hdev->discovery.uuids = NULL; spin_unlock(&hdev->discovery.lock); Now uuids == NULL and uuid_count != 0. So 'mgmt_device_found' -> 'is_filter_match' -> 'eir_has_uuids' receives non consistent discovery state, where NULL dereference of uuids happens. To fix it let's add discovery.lock around every read/write of uuid_count, uuids pair of struct members. It is also important to assign uuid_count value only after success kmemdup() allocation in start_service_discovery(), otherwise uuids is NULL, because kmemdup failed, but uuid_count is already assigned to non zero value. The following…