linux-kernel - Re: [PATCH] dmaengine: idxd: Fix double free in idxd_setup

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Message-ID: <5f44acad-0049-45d5-b1d9-1b4cd803c860@intel.com>
Date: Mon, 11 Aug 2025 08:43:19 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Dan Carpenter <dan.carpenter@...aro.org>,
 Shuai Xue <xueshuai@...ux.alibaba.com>,
 Colin Ian King <colin.i.king@...il.com>
Cc: Vinicius Costa Gomes <vinicius.gomes@...el.com>,
 Vinod Koul <vkoul@...nel.org>, Fenghua Yu <fenghuay@...dia.com>,
 dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] dmaengine: idxd: Fix double free in idxd_setup_wqs()



On 8/11/25 3:43 AM, Dan Carpenter wrote:
> The clean up in idxd_setup_wqs() has had a couple bugs because the error
> handling is a bit subtle.  It's simpler to just re-write it in a cleaner
> way.  The issues here are:
> 
> 1) If "idxd->max_wqs" is <= 0 then we call put_device(conf_dev) when
>    "conf_dev" hasn't been initialized.
> 2) If kzalloc_node() fails then again "conf_dev" is invalid.  It's
>    either uninitialized or it points to the "conf_dev" from the
>    previous iteration so it leads to a double free.
> 
> It's better to free partial loop iterations within the loop and then
> the unwinding at the end can handle whole loop iterations.  I also
> renamed the labels to describe what the goto does and not where the goto
> was located.
> 
> Fixes: 3fd2f4bc010c ("dmaengine: idxd: fix memory leak in error handling path of idxd_setup_wqs")
> Reported-by: Colin Ian King <colin.i.king@...il.com>
> Closes: https://lore.kernel.org/all/20250811095836.1642093-1-colin.i.king@gmail.com/
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
>  drivers/dma/idxd/init.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 35bdefd3728b..dda01a4398e1 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -189,27 +189,30 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
>  	idxd->wq_enable_map = bitmap_zalloc_node(idxd->max_wqs, GFP_KERNEL, dev_to_node(dev));
>  	if (!idxd->wq_enable_map) {
>  		rc = -ENOMEM;
> -		goto err_bitmap;
> +		goto err_free_wqs;
>  	}
> 
>  	for (i = 0; i < idxd->max_wqs; i++) {
>  		wq = kzalloc_node(sizeof(*wq), GFP_KERNEL, dev_to_node(dev));
>  		if (!wq) {
>  			rc = -ENOMEM;
> -			goto err;
> +			goto err_unwind;
>  		}
> 
>  		idxd_dev_set_type(&wq->idxd_dev, IDXD_DEV_WQ);
>  		conf_dev = wq_confdev(wq);
>  		wq->id = i;
>  		wq->idxd = idxd;
> -		device_initialize(wq_confdev(wq));
> +		device_initialize(conf_dev);
>  		conf_dev->parent = idxd_confdev(idxd);
>  		conf_dev->bus = &dsa_bus_type;
>  		conf_dev->type = &idxd_wq_device_type;
>  		rc = dev_set_name(conf_dev, "wq%d.%d", idxd->id, wq->id);
> -		if (rc < 0)
> -			goto err;
> +		if (rc < 0) {
> +			put_device(conf_dev);
> +			kfree(wq);
> +			goto err_unwind;
> +		}
> 
>  		mutex_init(&wq->wq_lock);
>  		init_waitqueue_head(&wq->err_queue);
> @@ -220,15 +223,20 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
>  		wq->enqcmds_retries = IDXD_ENQCMDS_RETRIES;
>  		wq->wqcfg = kzalloc_node(idxd->wqcfg_size, GFP_KERNEL, dev_to_node(dev));
>  		if (!wq->wqcfg) {
> +			put_device(conf_dev);
> +			kfree(wq);
>  			rc = -ENOMEM;
> -			goto err;
> +			goto err_unwind;
>  		}
> 
>  		if (idxd->hw.wq_cap.op_config) {
>  			wq->opcap_bmap = bitmap_zalloc(IDXD_MAX_OPCAP_BITS, GFP_KERNEL);
>  			if (!wq->opcap_bmap) {
> +				kfree(wq->wqcfg);
> +				put_device(conf_dev);
> +				kfree(wq);
>  				rc = -ENOMEM;
> -				goto err_opcap_bmap;
> +				goto err_unwind;
>  			}
>  			bitmap_copy(wq->opcap_bmap, idxd->opcap_bmap, IDXD_MAX_OPCAP_BITS);
>  		}
> @@ -239,13 +247,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
> 
>  	return 0;
> 
> -err_opcap_bmap:
> -	kfree(wq->wqcfg);
> -
> -err:
> -	put_device(conf_dev);
> -	kfree(wq);
> -
> +err_unwind:
>  	while (--i >= 0) {
>  		wq = idxd->wqs[i];
>  		if (idxd->hw.wq_cap.op_config)
> @@ -254,11 +256,10 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
>  		conf_dev = wq_confdev(wq);
>  		put_device(conf_dev);
>  		kfree(wq);
> -
>  	}
>  	bitmap_free(idxd->wq_enable_map);
> 
> -err_bitmap:
> +err_free_wqs:
>  	kfree(idxd->wqs);
> 
>  	return rc;
> --
> 2.47.2