linux-kernel - Re: [PATCH v1] dmaengine: idxd: Fix allowing write() from different address spaces

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Message-ID: <90296464-fec1-4885-a8bb-0f1fd21b6dab@intel.com>
Date: Mon, 21 Apr 2025 08:57:54 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Nathan Lynch <nathan.lynch@....com>,
 Vinicius Costa Gomes <vinicius.gomes@...el.com>,
 Vinod Koul <vkoul@...nel.org>, Arjan van de Ven <arjan@...ux.intel.com>,
 Nikhil Rao <nikhil.rao@...el.com>, dmaengine@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] dmaengine: idxd: Fix allowing write() from different
 address spaces



On 4/16/25 8:10 AM, Nathan Lynch wrote:
> Vinicius Costa Gomes <vinicius.gomes@...el.com> writes:
>> Check if the process submitting the descriptor belongs to the same
>> address space as the one that opened the file, reject otherwise.
> 
> I assume this can happen after a fork.
> 
> Do idxd_cdev_mmap() and idxd_cdev_poll() need similar protection?

Seems reasonable. Vinicius is on sabbatical. I'll respin his code and add the suggested checks. Thanks Nathan.

DJ

> 
>>
>> Fixes: 6827738dc684 ("dmaengine: idxd: add a write() method for applications to submit work")
>> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
>> ---
>>  drivers/dma/idxd/cdev.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
>> index ff94ee892339..373c622fcddc 100644
>> --- a/drivers/dma/idxd/cdev.c
>> +++ b/drivers/dma/idxd/cdev.c
>> @@ -473,6 +473,9 @@ static ssize_t idxd_cdev_write(struct file *filp, const char __user *buf, size_t
>>  	ssize_t written = 0;
>>  	int i;
>>  
>> +	if (current->mm != ctx->mm)
>> +		return -EPERM;
>> +
>>  	for (i = 0; i < len/sizeof(struct dsa_hw_desc); i++) {
>>  		int rc = idxd_submit_user_descriptor(ctx, udesc + i);
>>  
>> -- 
>> 2.49.0