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Mon, 04 May 2026 12:15:17 -0700 (PDT) Message-ID: <76904540-af95-4f8e-897d-845112094512@gmail.com> Date: Mon, 4 May 2026 15:15:16 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] Bluetooth: fix Set Public Address on controller in HCI_AUTO_OFF grace period To: Luiz Augusto von Dentz Cc: Marcel Holtmann , linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260430045522.7881-1-danilklishch@gmail.com> Content-Language: en-US From: Dan Klishch In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Luiz, On 5/4/26 2:27 PM, Luiz Augusto von Dentz wrote: > Hi Dan, > > On Thu, Apr 30, 2026 at 12:55 AM Dan Klishch wrote: >> >> When mgmt's Set Public Address command (and Set External Configuration) >> stages a configuration change, set_public_address() sets HCI_CONFIG and >> HCI_AUTO_OFF on the device and queues hci_power_on. The intent is for >> the queued power_on to run hci_dev_init_sync() -- which detects >> HCI_CONFIG and calls hdev->set_bdaddr() to program the new address into >> the firmware -- and then re-emit Index Added with the controller back in >> the boot-init grace period (HCI_UP=1, HCI_AUTO_OFF=1) so userspace can >> re-push pending config commands and drive a fresh Set Powered 1 cycle. >> >> The bug bites when the command is issued while the controller is in >> that same grace period itself -- the normal post-boot state, before >> bluetoothd has claimed the controller via Set Powered 1. In that state >> HCI_UP=1 and HCI_AUTO_OFF=1, so hdev_is_powered() is false (the command >> is accepted) but hci_power_on()'s "already up" early-return condition >> HCI_UP && HCI_MGMT && HCI_AUTO_OFF is true. The early-return path runs >> hci_powered_update_sync() -- which is the wrong thing for this case: >> neither hci_dev_init_sync() nor mgmt_index_added() runs. The result: >> >> - hdev->public_addr is recorded but never reaches the firmware via >> hdev->set_bdaddr(), >> - userspace sees Index Removed (from set_public_address) but no >> Index Added, leaving the controller invisible to mgmt clients; >> it is not in the configured, unconfigured or extended index list >> yet remains registered in the kernel. >> >> The other two starting states are fine: HCI_UP=0 falls through to the >> full hci_dev_do_open() path (correct); HCI_UP=1 with HCI_AUTO_OFF=0 >> makes hdev_is_powered() true, so set_public_address() rejects with >> MGMT_STATUS_REJECTED before queueing power_on at all. >> >> Fix: at the top of hci_power_on(), if HCI_CONFIG is pending and we are >> in the affected grace-period state (HCI_UP, HCI_MGMT, !HCI_RFKILLED), >> close the device first. The early-return condition then fails and we >> fall through to hci_dev_do_open() -> hci_dev_init_sync(), which honors >> HCI_CONFIG by invoking hdev->set_bdaddr(); the post-open block then >> re-emits Index Added via the existing HCI_CONFIG branch. >> >> hci_dev_close_sync() clears HCI_AUTO_OFF as a side effect of going >> through the regular power-down path, but set_public_address() had set >> it deliberately so the post-reopen state matches the boot-init grace >> period that mgmt clients expect ("treat as new one" per the protocol >> contract). Several mgmt commands -- Set Privacy, Set Wideband Speech, >> Set LE, Set BR/EDR, etc. -- gate on !hdev_is_powered(), and bluetoothd >> expects to push them during this window before issuing Set Powered 1 >> itself. Restore HCI_AUTO_OFF after the close so hdev_is_powered() == >> false again. >> >> This matches the documented behavior for Set Public Address on a >> fully-configured controller ("Once the address has been successfully >> changed an Index Added event will be sent.") >> >> Assisted-by: Claude:claude-opus-4-7 >> Signed-off-by: Dan Klishch >> --- >> net/bluetooth/hci_core.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> --- a/net/bluetooth/hci_core.c >> +++ b/net/bluetooth/hci_core.c >> @@ -948,6 +948,14 @@ static void hci_power_on(struct work_struct *work) >> >> BT_DBG("%s", hdev->name); >> >> + if (hci_dev_test_flag(hdev, HCI_CONFIG) && >> + hci_dev_test_flag(hdev, HCI_MGMT) && >> + !hci_dev_test_flag(hdev, HCI_RFKILLED) && >> + test_bit(HCI_UP, &hdev->flags)) { >> + hci_dev_do_close(hdev); >> + hci_dev_set_flag(hdev, HCI_AUTO_OFF); >> + } >> + >> if (test_bit(HCI_UP, &hdev->flags) && >> hci_dev_test_flag(hdev, HCI_MGMT) && >> hci_dev_test_and_clear_flag(hdev, HCI_AUTO_OFF)) { >> >> --- >> >> Claude was able to fully convince me that the patch and the explanation >> are correct. Moreover, this indeed fixed a problem I had with a custom >> patched bluetoothd that happened to override public-addr in the 2 >> second post-boot window. However, both the patch and commit description >> are fully AI-generated. > > This doesn't inspire much confidence, though. Have you at least tried > it yourself? Perhaps we need to ask Claude to first add a test to > mgmt-tester to ensure it actually fixes something rather than just > hallucinating. Most models are not actually very critical of their > proposals if there is nothing to validate their claims with. > I did test this indeed. The bluez patch I mentioned: https://gist.github.com/DanShaders/4d280096a5f0f2f45ce07028cbd36761 (this is yet another AI slop, sorry!; I just wanted something quick for myself). Without the kernel patch, MGMT_OP_SET_PUBLIC_ADDRESS is just silently swallowed, adapter is removed, and then the userspace never sees it again. Claude says it cannot easily add an in-tree test for the patch without additional changes in vhci to support setting public address. Should I tell it to do a 3 commit series (set public addr on vhci; this; a test) and send as V2? One more question: seems like CI is angry on me because I included the `Assisted-by: Claude:claude-opus-4-7` tag as per https://docs.kernel.org/process/coding-assistants.html . Should I remove it? (Resending since I accidentally chose "Reply" instead of "Reply All" the first time, I'm not very used to mailing lists)