linux-kernel - Re: [PATCH 1/1] sched.h: always_inline alloc_tag

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]

Message-ID: <CAJuCfpHvNjFQYU0zHOuang2mNOLNHHiNfaWACPWuP4mSMX_OmQ@mail.gmail.com>
Date: Wed, 3 Jul 2024 21:07:56 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	vincent.guittot@...aro.org, kent.overstreet@...ux.dev, 
	linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 1/1] sched.h: always_inline alloc_tag_{save|restore} to
 fix modpost warnings

On Wed, Jul 3, 2024 at 8:54 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 3 Jul 2024 20:46:11 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > Ok, I confirmed that the warning is happening due to the access to
> > "current" from alloc_tag_save()/alloc_tag_restore() functions. I guess
> > when these functions access "thread_info" variable:
> > https://elixir.bootlin.com/linux/v6.10-rc6/source/arch/xtensa/include/asm/thread_info.h#L96,
> > compiler flags that because the variable is on the stack of an __init
> > function while alloc_tag_save()/alloc_tag_restore() when not inlined
> > are from .text section.
>
> Well, is the warning legitimate?  I don't see why an automatic variable
> of an __init function should be considered to be .init storage - we can
> assume it won't become an invalid reference while the .init function is
> executing?

I don't think it's really a problem. __init function is executing, it
calls a function from .text (say alloc_tag_save() that was not
inlined) which in turn calls get_current(), which returns a pointer
somewhere inside __initdata. That should be fine since this can only
happen during init stage. If this call happens after init,
get_current() can't return a pointer from __initdata. If it does then
we have a much bigger problem.

>