linux-kernel - Re: [PATCH v3] target: close target_put_sess_cmd() vs. core_tmr_abort

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Message-ID: <20130319015354.GA21045@kroah.com>
Date:	Mon, 18 Mar 2013 18:53:54 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Jörn Engel <joern@...fs.org>
Cc:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	linux-kernel@...r.kernel.org,
	target-devel <target-devel@...r.kernel.org>
Subject: Re: [PATCH v3] target: close target_put_sess_cmd() vs.
 core_tmr_abort_task() race

On Mon, Mar 18, 2013 at 07:34:13PM -0400, Jörn Engel wrote:
> And because I'm lame and stupid, here's v3.
> 
> It is possible for one thread to to take se_sess->sess_cmd_lock in
> core_tmr_abort_task() before taking a reference count on
> se_cmd->cmd_kref, while another thread in target_put_sess_cmd() drops
> se_cmd->cmd_kref before taking se_sess->sess_cmd_lock.
> 
> This introduces kref_put_and_lock() and uses it in
> target_put_sess_cmd() to close the race window.
> 
> Signed-off-by: Joern Engel <joern@...fs.org>
> ---
>  drivers/target/target_core_transport.c |   17 +++++++++++------
>  include/linux/kref.h                   |   26 ++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> index 04ec9cb..b98c158 100644
> --- a/drivers/target/target_core_transport.c
> +++ b/drivers/target/target_core_transport.c
> @@ -2207,21 +2207,19 @@ static void target_release_cmd_kref(struct kref *kref)
>  {
>  	struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
>  	struct se_session *se_sess = se_cmd->se_sess;
> -	unsigned long flags;
>  
> -	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
>  	if (list_empty(&se_cmd->se_cmd_list)) {
> -		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
> +		spin_unlock(&se_sess->sess_cmd_lock);

Wait, who has this locked?  You took out the call to spin_lock_* above.

And why not _irqstore() anymore?

thanks,

greg k-h
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