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