linux-kernel - Re: [v8] misc: pci_endpoint_test: Fix overflow of bar

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Message-ID: <d79d5a72-d1b0-4442-a0a3-e53516726204@163.com>
Date: Mon, 6 Jan 2025 23:32:33 +0800
From: Hans Zhang <18255117159@....com>
To: Niklas Cassel <cassel@...nel.org>
Cc: manivannan.sadhasivam@...aro.org, kw@...ux.com, kishon@...nel.org,
 arnd@...db.de, gregkh@...uxfoundation.org, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, rockswang7@...il.com
Subject: Re: [v8] misc: pci_endpoint_test: Fix overflow of bar_size



On 2025/1/6 19:49, Niklas Cassel wrote:
> Doing a:
> $ git grep -A 10 "IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT"
> does not show very many hits, which suggests that this is not the proper
> way to solve this.
> 
> I don't know the proper solution to this. How is resource_size_t handled
> in other PCI driver when being built on with 32-bit PHYS_ADDR_T ?
> 
> Can't you just cast the resource_size_t to u64 before doing the division?

Hi Niklas,

Modify as follows, if you have no opinion, I will fix the next version.

>> ---
>>   drivers/misc/pci_endpoint_test.c | 12 +++++++++---
>>   1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
>> index 3aaaf47fa4ee..50d4616119af 100644
>> --- a/drivers/misc/pci_endpoint_test.c
>> +++ b/drivers/misc/pci_endpoint_test.c
>> @@ -280,10 +280,11 @@ static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
>>   static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
>>   				  enum pci_barno barno)
>>   {
>> -	int j, bar_size, buf_size, iters, remain;
>>   	void *write_buf __free(kfree) = NULL;
>>   	void *read_buf __free(kfree) = NULL;
>>   	struct pci_dev *pdev = test->pdev;
>> +	int j, buf_size, iters, remain;
>> +	resource_size_t bar_size;

Fix resource_size_t to u64 bar_size.
u64 bar_size;

>>   
>>   	if (!test->bar[barno])
>>   		return false;
>> @@ -307,13 +308,18 @@ static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
>>   	if (!read_buf)
>>   		return false;
>>   
>> -	iters = bar_size / buf_size;
>> +	if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT)) {
>> +		remain = do_div(bar_size, buf_size);
>> +		iters = bar_size;
>> +	} else {
>> +		iters = bar_size / buf_size;
>> +		remain = bar_size % buf_size;
>> +	}

Removed IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT), Execute the following code.

remain = do_div(bar_size, buf_size);
iters = bar_size;

>>   	for (j = 0; j < iters; j++)
>>   		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
>>   						 write_buf, read_buf, buf_size))
>>   			return false;
>>   
>> -	remain = bar_size % buf_size;
>>   	if (remain)
>>   		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters,
>>   						 write_buf, read_buf, remain))
>>
>> base-commit: ccb98ccef0e543c2bd4ef1a72270461957f3d8d0
>> -- 
>> 2.25.1
>>

Best regards
Hans