linux-kernel - Re: [PATCH v2] ocfs2: Fix a use after free on error

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Date:   Tue, 2 Feb 2021 20:08:28 +0800
From:   Joseph Qi <joseph.qi@...ux.alibaba.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Mark Fasheh <mark@...heh.com>
Cc:     Joel Becker <jlbec@...lplan.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Takashi Iwai <tiwai@...e.de>, Jens Axboe <axboe@...nel.dk>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Jiri Slaby <jirislaby@...nel.org>, ocfs2-devel@....oracle.com,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] ocfs2: Fix a use after free on error



On 2/2/21 7:32 PM, Dan Carpenter wrote:
> The error handling in this function frees "reg" but it is still on the
> "o2hb_all_regions" list so it will lead to a use after freew.  Joseph Qi
> points out that we need to clear the bit in the "o2hb_region_bitmap" as
> well
> 
> Fixes: 1cf257f51191 ("ocfs2: fix memory leak")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Looks good.
Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>

> ---
> v2: The first version didn't clear the bit.
> 
>  fs/ocfs2/cluster/heartbeat.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
> index 0179a73a3fa2..12a7590601dd 100644
> --- a/fs/ocfs2/cluster/heartbeat.c
> +++ b/fs/ocfs2/cluster/heartbeat.c
> @@ -2042,7 +2042,7 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g
>  			o2hb_nego_timeout_handler,
>  			reg, NULL, &reg->hr_handler_list);
>  	if (ret)
> -		goto free;
> +		goto remove_item;
>  
>  	ret = o2net_register_handler(O2HB_NEGO_APPROVE_MSG, reg->hr_key,
>  			sizeof(struct o2hb_nego_msg),
> @@ -2057,6 +2057,12 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g
>  
>  unregister_handler:
>  	o2net_unregister_handler_list(&reg->hr_handler_list);
> +remove_item:
> +	spin_lock(&o2hb_live_lock);
> +	list_del(&reg->hr_all_item);
> +	if (o2hb_global_heartbeat_active())
> +		clear_bit(reg->hr_region_num, o2hb_region_bitmap);
> +	spin_unlock(&o2hb_live_lock);
>  free:
>  	kfree(reg);
>  	return ERR_PTR(ret);
>