Re: [PATCH 4/9] EDAC/versalnet: Fix device_register() error handling in init_one_mc()

["Pandey, Radhey Shyam" <radheys@amd.com>]

On 7/24/2026 10:49 PM, Shubhrajyoti Datta wrote:
> From: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
> 
> When device_register() fails, it must be followed by put_device()
> rather than kfree(), because device_register() calls
> device_initialize() which sets up the device refcount. The matching
> release function versal_edac_release() handles the actual kfree().
> 
> To simplify error handling and avoid complex unwinding, split
> device_register() into device_initialize() and device_add().
> Initialize the device early so put_device() can be used in all
> error paths.
> 
> Fixes: d5fe2fec6c40 ("EDAC: Add a driver for the AMD Versal NET DDR controller")
> Cc: stable@vger.kernel.org
> Signed-off-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
checkpatch reports - warn.

WARNING: Non-standard signature: Co-authored-by:
#20:
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

> Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>

Nit - this is Co-developed-by: candidate as you did changes on top.

> ---
> 
>   drivers/edac/versalnet_edac.c | 28 ++++++++++++++--------------
>   1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/edac/versalnet_edac.c b/drivers/edac/versalnet_edac.c
> index 03b6e0958f17..3c9eaea5a106 100644
> --- a/drivers/edac/versalnet_edac.c
> +++ b/drivers/edac/versalnet_edac.c
> @@ -785,7 +785,7 @@ static int init_one_mc(struct mc_priv *priv, int i)
>   	char name[MC_NAME_LEN];
>   	struct device *dev;
>   	enum dev_type dt;
> -	int rc;
> +	int rc = -ENOMEM;
>   
>   	config = priv->adec[CONF + i * ADEC_NUM];
>   	num_chans = FIELD_GET(MC5_NUM_CHANS_MASK, config);
> @@ -817,23 +817,23 @@ static int init_one_mc(struct mc_priv *priv, int i)
>   	layers[1].size = num_chans;
>   	layers[1].is_virt_csrow = false;
>   
> -	rc = -ENOMEM;
>   	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>   	if (!dev)
>   		return rc;
>   
> -	mci = edac_mc_alloc(i, ARRAY_SIZE(layers), layers, sizeof(struct mc_priv));
> -	if (!mci) {
> -		edac_printk(KERN_ERR, EDAC_MC, "Failed memory allocation for MC%d\n", i);
> -		goto err_dev_free;
> -	}
> -
>   	sprintf(name, "versal-net-ddrmc5-edac-%d", i);
>   
>   	dev->init_name = name;
>   	dev->release = versal_edac_release;
> +	device_initialize(dev);
>   

There was a comment earlier from sashiko: After splitting
device_register(), the edac_mc_alloc() failure path calls
put_device() with dev->init_name still pointing at a stack
buffer before device_add() copies it. That's unsafe in
principle (dev_name() would follow init_name) and worse with
CONFIG_DEBUG_KOBJECT_RELEASE deferral.


> -	rc = device_register(dev);
> +	mci = edac_mc_alloc(i, ARRAY_SIZE(layers), layers, sizeof(struct mc_priv));
> +	if (!mci) {
> +		edac_printk(KERN_ERR, EDAC_MC, "Failed memory allocation for MC%d\n", i);
> +		goto err_put_dev;
> +	}
> +
> +	rc = device_add(dev);
>   	if (rc)
>   		goto err_mc_free;
>   
> @@ -843,7 +843,7 @@ static int init_one_mc(struct mc_priv *priv, int i)
>   	rc = edac_mc_add_mc(mci);
>   	if (rc) {
>   		edac_printk(KERN_ERR, EDAC_MC, "Failed to register MC%d with EDAC core\n", i);
> -		goto err_unreg;
> +		goto err_dev_del;
>   	}
>   
>   	priv->mci[i] = mci;
> @@ -851,12 +851,12 @@ static int init_one_mc(struct mc_priv *priv, int i)
>   
>   	return 0;
>   
> -err_unreg:
> -	device_unregister(mci->pdev);
> +err_dev_del:
> +	device_del(dev);
>   err_mc_free:
>   	edac_mc_free(mci);
> -err_dev_free:
> -	kfree(dev);
> +err_put_dev:
> +	put_device(dev);
>   
>   	return rc;
>   }