linux-kernel - Re: [PATCH 2/2] xen: privcmd: Fix possible access to a freed kirqfd instance

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Message-ID: <caa4f006-6c74-4e16-961f-23ea90e26606@suse.com>
Date: Tue, 2 Jul 2024 12:15:57 +0200
From: Juergen Gross <jgross@...e.com>
To: Viresh Kumar <viresh.kumar@...aro.org>,
 Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>,
 Alex Bennée <alex.bennee@...aro.org>,
 Manos Pitsidianakis <manos.pitsidianakis@...aro.org>,
 Paolo Bonzini <pbonzini@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
 xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] xen: privcmd: Fix possible access to a freed kirqfd
 instance

On 18.06.24 11:42, Viresh Kumar wrote:
> Nothing prevents simultaneous ioctl calls to privcmd_irqfd_assign() and
> privcmd_irqfd_deassign(). If that happens, it is possible that a kirqfd
> created and added to the irqfds_list by privcmd_irqfd_assign() may get
> removed by another thread executing privcmd_irqfd_deassign(), while the
> former is still using it after dropping the locks.
> 
> This can lead to a situation where an already freed kirqfd instance may
> be accessed and cause kernel oops.
> 
> Use SRCU locking to prevent the same, as is done for the KVM
> implementation for irqfds.
> 
> Reported-by: Al Viro <viro@...iv.linux.org.uk>
> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen


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