linux-kernel - Re: [PATCH net v3] ptp: prevent possible ABBA deadlock in ptp_clock

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: <20250721122033.3pszhnhqtgs2swt6@skbuf>
Date: Mon, 21 Jul 2025 15:20:33 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: Jeongjun Park <aha310510@...il.com>
Cc: richardcochran@...il.com, andrew+netdev@...n.ch, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	yangbo.lu@....com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot+7cfb66a237c4a5fb22ad@...kaller.appspotmail.com
Subject: Re: [PATCH net v3] ptp: prevent possible ABBA deadlock in
 ptp_clock_freerun()

On Mon, Jul 21, 2025 at 08:36:17PM +0900, Jeongjun Park wrote:
> However, I think ptp->n_vclocks_mux also needs to be annotating lock
> subclass because there may be false positives due to recursive locking
> between physical and virtual clocks.

Did you miss the part where I reiterated, in my review comment to your v2,
that after commit 5ab73b010cad ("ptp: fix breakage after ptp_vclock_in_use()
rework"), ptp->n_vclocks_mux is only acquired by physical clocks, not by
virtual clocks?

Also, in general I think it would be useful to include more substantial
pieces of my explanation in your commit message, or link to it in its
entirety. I am worried that the info from it becomes denatured, for
example this piece from your commit message: "Functions like
clock_adjtime() can only be called with physical clocks." I did not say
that, I said that **in order for the clock_adjtime() call to acquire
&ptp->n_vclocks_mux**, then the clock must have been physical.
In general, adjusting a virtual clock is perfectly possible, thus your
restatement is false, and it proves a lack of understanding of the
ptp->n_vclocks_mux locking convention.