linux-kernel - Re: [PATCH next] vhost_task: after freeing vhost_task it should not be accessed in vhost_task

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Message-ID: <b959b82a-510f-45c0-9e06-acf526c2f4a1@oracle.com>
Date: Tue, 30 Apr 2024 11:23:04 -0500
From: Mike Christie <michael.christie@...cle.com>
To: Edward Adam Davis <eadavis@...com>,
        syzbot+98edc2df894917b3431f@...kaller.appspotmail.com
Cc: jasowang@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mst@...hat.com, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, virtualization@...ts.linux.dev
Subject: Re: [PATCH next] vhost_task: after freeing vhost_task it should not
 be accessed in vhost_task_fn

On 4/30/24 8:05 AM, Edward Adam Davis wrote:
>  static int vhost_task_fn(void *data)
>  {
>  	struct vhost_task *vtsk = data;
> @@ -51,7 +51,7 @@ static int vhost_task_fn(void *data)
>  			schedule();
>  	}
>  
> -	mutex_lock(&vtsk->exit_mutex);
> +	mutex_lock(&exit_mutex);
>  	/*
>  	 * If a vhost_task_stop and SIGKILL race, we can ignore the SIGKILL.
>  	 * When the vhost layer has called vhost_task_stop it's already stopped
> @@ -62,7 +62,7 @@ static int vhost_task_fn(void *data)
>  		vtsk->handle_sigkill(vtsk->data);
>  	}
>  	complete(&vtsk->exited);
> -	mutex_unlock(&vtsk->exit_mutex);
> +	mutex_unlock(&exit_mutex);
>  

Edward, thanks for the patch. I think though I just needed to swap the
order of the calls above.

Instead of:

complete(&vtsk->exited);
mutex_unlock(&vtsk->exit_mutex);

it should have been:

mutex_unlock(&vtsk->exit_mutex);
complete(&vtsk->exited);

If my analysis is correct, then Michael do you want me to resubmit a
patch on top of your vhost branch or resubmit the entire patchset?