[PATCH v3 0/3] Bluetooth: SMP: Serialize root channel updates

[Cen Zhang <zzzccc427@gmail.com>]

The SMP root channels in hdev->smp_data and hdev->smp_bredr_data are
used by HCI event processing under hdev->lock and by SMP receive
callbacks on hdev->workqueue. Power-off already removes them under
hdev->lock in hci_dev_close_sync(). Two other writers do not serialize
with these users:

  1/3 The force_bredr_smp debugfs switch creates and removes the BR/EDR
      root without hdev->lock. A connection confirmation can see a root
      whose operations are not set yet, and a disable can race with
      power-off and release the channel twice. Take hdev->lock in the
      writer, and skip the deletion when power-off already emptied the
      slot.

  3/3 smp_register() replaces both roots when management powers on a
      controller that is already up with HCI_AUTO_OFF set, while HCI
      event processing and SMP receive callbacks can still be using the
      old roots. Run the registration on hdev->workqueue, where it ran
      before commit 2ff13894cfb8 ("Bluetooth: Perform HCI update for
      power on synchronously"), and hold hdev->lock while it replaces
      the roots. The caller waits for the work with the request lock
      held but not hdev->lock, which HCI event processing on that
      workqueue takes.

Patch 2/3 makes that hold for every caller: hci_power_on() runs the same
power-on update for a controller in the HCI_AUTO_OFF window, but has
done so without the request lock since commit cf75ad8b41d2 ("Bluetooth:
hci_sync: Convert MGMT_SET_POWERED").

smp_register() still warns when it replaces the channels on that path.
This series only makes the replacement safe.

Cen Zhang (3):
  Bluetooth: SMP: Serialize forced BR/EDR channel changes
  Bluetooth: hci_core: Hold the request lock for the power-on update
  Bluetooth: SMP: Serialize root channel replacement

 net/bluetooth/hci_core.c    |  3 +++
 net/bluetooth/hci_debugfs.c |  2 ++
 net/bluetooth/smp.c         | 38 +++++++++++++++++++++++++++++++++++--
 net/bluetooth/smp.h         |  3 ++-
 4 files changed, 43 insertions(+), 3 deletions(-)

---
Changes in v3:
- Address the hci_power_on() path that reaches smp_register() without the
  request lock, raised by Sashiko: https://sashiko.dev/#/patchset/99158
- Add patch 2, which takes the request lock in hci_power_on() again, and
  correct the locking description of patch 3; the code of patches 1 and 3 is
  unchanged.

Changes in v2:
- Address the CheckPatch and GitLint long-line failures reported by the
  Bluetooth CI: https://patchwork.kernel.org/series/1197223/
- Trim the crash reports in both commit messages to the headline, call trace
  and allocation/free stacks; no code changes.

Link to v1: https://lore.kernel.org/r/pm-bluetooth-objects-candidate-0184-v7-c26e53b52c260063ab6a-0@gmail.com
Link to v2: https://lore.kernel.org/r/pm-bluetooth-objects-candidate-0184-v8-60106ad0c49170f5bfb4-0@gmail.com