linux-kernel - Re: [PATCH v5 2/2] x86/MCE/AMD: Fix memory leak when `threshold_create

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Date:   Mon, 28 Mar 2022 10:05:22 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ammar Faizi <ammarfaizi2@...weeb.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Alviro Iskandar Setiawan <alviro.iskandar@...il.com>,
        Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Yazen Ghannam <yazen.ghannam@....com>,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, gwml@...r.gnuweeb.org, x86@...nel.org
Subject: Re: [PATCH v5 2/2] x86/MCE/AMD: Fix memory leak when
 `threshold_create_bank()` fails

On Mon, Mar 28, 2022 at 11:12:53AM +0700, Ammar Faizi wrote:
> Although, I am not sure if that 100% guarantees mce_threshold_remove_device()
> will not mess up with the interrupt (e.g. freeing the data while the interrupt
> reading it), unless we're using RCU stuff.
> 
> What do you think?

I would've said it doesn't matter but that thresholding device creation
is part of hotplug and it can happen multiple times even *after* the
interrupt vector has been set during setup so a potential teardown and
concurrent thresholding interrupt firing might really hit in a not fully
initialized/cleaned up state so yeah, let's do Yazen's thing.

The alternative would be the temporarily re-assign mce_threshold_vector
to default_threshold_interrupt while setup is being done but that's not
really necessary atm.

But call that helper function __threshold_remove_device().

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette