[PATCH v1] misc: fastrpc: Fix channel resource access in device_open

[Dmitry Baryshkov]

On Sat, May 17, 2025 at 12:54:32PM +0530, Ekansh Gupta wrote:
> During rpmsg_probe, fastrpc device nodes are created first, then
> channel specific resources are initialized, followed by
> of_platform_populate, which triggers context bank probing. This
> sequence can cause issues as applications might open the device
> node before channel resources are initialized or the session is
> available, leading to problems. For example, spin_lock is initialized
> after the device node creation, but it is used in device_open,
> potentially before initialization. Add a check in device_open for
> rpdev and update rpdev at the end of rpmsg_probe to resources are
> available before applications allocate sessions.

Can we fix this by registering the device node after initializing
channel resources?

> 
> Fixes: f6f9279f2bf0e ("misc: fastrpc: Add Qualcomm fastrpc basic driver model")
> Cc: stable at kernel.org
> Signed-off-by: Ekansh Gupta <ekansh.gupta at oss.qualcomm.com>
> ---
>  drivers/misc/fastrpc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 7b7a22c91fe4..40c7fa048ba7 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1568,6 +1568,9 @@ static int fastrpc_device_open(struct inode *inode, struct file *filp)
>  	fdevice = miscdev_to_fdevice(filp->private_data);
>  	cctx = fdevice->cctx;
>  
> +	if (!cctx->rpdev)
> +		return -ENODEV;
> +
>  	fl = kzalloc(sizeof(*fl), GFP_KERNEL);
>  	if (!fl)
>  		return -ENOMEM;
> @@ -2363,12 +2366,13 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>  	spin_lock_init(&data->lock);
>  	idr_init(&data->ctx_idr);
>  	data->domain_id = domain_id;
> -	data->rpdev = rpdev;
>  
>  	err = of_platform_populate(rdev->of_node, NULL, NULL, rdev);
>  	if (err)
>  		goto populate_error;
>  
> +	data->rpdev = rpdev;
> +
>  	return 0;
>  
>  populate_error:
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry