linux-kernel - Re: Possible hungtask issue will be introduced with device_lock() in uevent

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: <2025010443-blighted-monogamy-f125@gregkh>
Date: Sat, 4 Jan 2025 09:14:23 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: "zhangzekun (A)" <zhangzekun11@...wei.com>
Cc: dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
	rafael.j.wysocki@...el.com, regressions@...ts.linux.dev,
	tj@...nel.org, alex.williamson@...hat.com, chenjun102@...wei.com
Subject: Re: Possible hungtask issue will be introduced with device_lock() in
 uevent_show()

On Sat, Jan 04, 2025 at 02:02:54PM +0800, zhangzekun (A) wrote:
> 
> 
> 在 2024/12/31 16:26, Greg KH 写道:
> > On Tue, Dec 31, 2024 at 03:56:08PM +0800, Zhang Zekun wrote:
> > > Hi, Dan, Greg,
> > > 
> > > We have found a potential tungtask issue has been introduce by commit 9a71892cbcdb ("Revert "driver core: Fix uevent_show() vs driver detach race""), which revert the rcu in device_uevent but reintroduce the device_lock() in uevent_show(). The reproduce procedure is quite simple:
> > 
> > The revert just puts the original logic back in place, so this is not
> > anything new that has been introduced, right?  It's just that the
> > attempted fix didn't work, so a different fix needs to happen.
> Hi, Greg,
> 
> Yes, there is nothing new introduced here. We have been testing the rcu fix
> (commit 15fffc6a5624 ("driver core: Fix uevent_show() vs driver detach
> race")) for monthes but has not obersved problems.

That's great, but other people did report problems, which can't be
ignored.

> Noticing that, brmails+k write in bugzilla "Also, I can't say why the issue
> appeared in the past even without this commit being present, as I haven't
> bisected any kernel version before v6.6.45.". I doubt that there could still
> have problem described in bugzilla [1] even if commit c0a40097f0bc
> ("drivers: core: synchronize really_probe() and dev_uevent()") has been
> reverted, and the problem is not directly introduced by rcu in dev_uevent.
> 
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=219244

So you think that the bug report is wrong?  Ok, then you might need to
take the time to prove it :)

If you feel this should be added back, please feel free to resubmit it
with the new information as to why it should be ok now to apply it.

thanks,

greg k-h