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From: "Jürgen Groß" <jgross@suse.com>
To: "Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
	Stefano Stabellini <sstabellini@kernel.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from_irq()
Date: Fri, 22 May 2020 10:18:23 +0200	[thread overview]
Message-ID: <5839ff92-92e4-667a-8ed1-f5f9f3453299@suse.com> (raw)
In-Reply-To: <c36de3eb-c0ad-45e1-e08b-cb7d86d197f6@oracle.com>

On 21.05.20 23:57, Boris Ostrovsky wrote:
> On 5/21/20 2:46 PM, Marek Marczykowski-Górecki wrote:
>> 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
>>
> 
> 
> Thanks. Do we know what the race is? Is it because an event is being
> delivered from a dying guest who is in the process of tearing down event
> channels?

Missing synchronization between event channel (de-)allocation and
handling.

I have a patch sitting here, just didn't have the time to do some proper
testing and sending it out.


Juergen

      reply	other threads:[~2020-05-22  8:18 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19  7:14 [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from_irq() Juergen Gross
2020-03-19 16:01 ` Boris Ostrovsky
2020-05-21 17:22 ` Boris Ostrovsky
2020-05-21 18:46   ` Marek Marczykowski-Górecki
2020-05-21 21:57     ` Boris Ostrovsky
2020-05-22  8:18       ` Jürgen Groß [this message]

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