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

[Ekansh Gupta]

On 5/18/2025 4:33 PM, Dmitry Baryshkov wrote:
> 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?
Ack.

Thanks.
>
>> 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
>>