linux-kernel - Re: xfs : WARNING: possible circular locking dependency detected

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

Date: Wed, 17 Apr 2024 23:56:08 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Dave Chinner <david@...morbit.com>
Cc: Xiubo Li <xiubli@...hat.com>, linux-xfs@...r.kernel.org,
	chandan.babu@...cle.com, djwong@...nel.org,
	linux-kernel@...r.kernel.org,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	kasan-dev@...glegroups.com
Subject: Re: xfs : WARNING: possible circular locking dependency detected

Adding the KASAN maintainer so that we actuall have a chane of
fixing this instead of a rant that just gets lost on the xfs list..

On Thu, Apr 18, 2024 at 03:04:24PM +1000, Dave Chinner wrote:
> The only krealloc() in this path is:
> 
> 	new = krealloc(ifp->if_data, new_size,
>                         GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_NOFAIL);
> 
> And it explicitly uses __GFP_NOLOCKDEP to tell lockdep not to warn
> about this allocation because of this false positive situation.
> 
> Oh. I've seen this before. This is a KASAN bug, and I'm pretty sure
> I've posted a patch to fix it a fair while back that nobody seemed
> to care about enough to review or merge it.
> 
> That is: kasan_save_stack() is doing a fixed GFP_KERNEL allocation
> in an context where GFP_KERNEL allocations are known to generate
> lockdep false positives.  This occurs depsite the XFS and general
> memory allocation code doing exactly the right thing to avoid the
> lockdep false positives (i.e. using and obeying __GFP_NOLOCKDEP).
> 
> The kasan code ends up in stack_depot_save_flags(), which does a
> GFP_KERNEL allocation but filters out __GFP_NOLOCKDEP and does not
> add it back. Hence kasan generates the false positive lockdep
> warnings, not the code doing the original allocation.
> 
> kasan and/or stack_depot_save_flags() needs fixing here.
> 
> -Dave.
> -- 
> Dave Chinner
> david@...morbit.com
> 
---end quoted text---