linux-kernel - Re: [PATCH] Bluetooth: hci_h5: avoid sending two SYNC messages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aKotJuaUB2V6zdKc@macbookair.lan>
Date: Sat, 23 Aug 2025 14:05:42 -0700
From: Javier Nieto <jgnieto@...stanford.edu>
To: Paul Menzel <pmenzel@...gen.mpg.de>
Cc: luiz.dentz@...il.com, marcel@...tmann.org,
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: hci_h5: avoid sending two SYNC messages

Dear Paul,

> Great commit message, thank you. I´d appreciate it if you documented your
> test environment, and maybe paste the logs (for the timestamps) before and
> after, so others could easily reproduce the issue.

Appologies for that. My test environment is a MangoPi MQ-Pro board
(with a Realtek RTL8723DS Bluetooth chip) running the tip of
bluetooth-next, although I also observed this issue on 6.8 kernel.
Originally, I spotted it using a logic analyzer on the UART PCB traces.
I added a temporary log message to h5_link_control(), which prints the
first byte and the length of the packet being sent. Here is the relevant
part before the patch:

[   67.328445] Bluetooth: h5_link_control sending 1 with len 2
[   67.432393] Bluetooth: h5_link_control sending 1 with len 2
[   67.436424] Bluetooth: h5_link_control sending 3 with len 3
[   67.436592] Bluetooth: h5_link_control sending 2 with len 2
[   67.436693] Bluetooth: h5_link_control sending 3 with len 3
[   67.439510] Bluetooth: h5_link_control sending 2 with len 2
[   67.440004] Bluetooth: h5_link_control sending 4 with len 2
[   67.440030] Bluetooth: h5_link_control sending 3 with len 3

And here after the patch:

[   67.498228] Bluetooth: h5_link_control sending 1 with len 2
[   67.501444] Bluetooth: h5_link_control sending 3 with len 3
[   67.501615] Bluetooth: h5_link_control sending 2 with len 2
[   67.504976] Bluetooth: h5_link_control sending 2 with len 2
[   67.505141] Bluetooth: h5_link_control sending 4 with len 2
[   67.505168] Bluetooth: h5_link_control sending 3 with len 3

Notice that in the first case, two SYNC packets (type 1) are sent, one 100ms
after the other, while in the second case only one is sent. In both
cases, using bluetoothctl to connect to a device later on works fine.

Thanks for the feedback,

Javier