linux-kernel - Re: [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from

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Message-ID: <20200521184602.GP98582@mail-itl>
Date:   Thu, 21 May 2020 20:46:02 +0200
From:   Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     Juergen Gross <jgross@...e.com>, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org,
        Stefano Stabellini <sstabellini@...nel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] xen/events: avoid NULL pointer dereference in
 evtchn_from_irq()

On Thu, May 21, 2020 at 01:22:03PM -0400, Boris Ostrovsky wrote:
> On 3/19/20 3:14 AM, Juergen Gross wrote:
> > There have been reports of races in evtchn_from_irq() where the info
> > pointer has been NULL.
> >
> > Avoid that case by testing info before dereferencing it.
> >
> > In order to avoid accessing a just freed info structure do the kfree()
> > via kfree_rcu().
> 
> 
> Looks like noone ever responded to this.
> 
> 
> This change looks fine but is there a background on the problem? I
> looked in the archives and didn't find the relevant discussion.

Here is the original bug report:
https://xen.markmail.org/thread/44apwkwzeme4uavo

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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