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

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Message-ID: <Z3vDLcq9kWL4ueq7@ryzen>
Date: Mon, 6 Jan 2025 12:49:01 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Hans Zhang <18255117159@....com>
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 Sat, Jan 04, 2025 at 11:16:52PM +0800, Hans Zhang wrote:
> With 8GB BAR2, running pcitest -b 2 fails with "TEST FAILED".
> 
> The return value of the `pci_resource_len` interface is not an integer.
> Using `pcitest` with an 8GB BAR2, the bar_size of integer type will
> overflow.
> 
> Change the data type of bar_size from integer to resource_size_t, to fix
> the above issue.
> 
> Signed-off-by: Hans Zhang <18255117159@....com>
> Reviewed-by: Niklas Cassel <cassel@...nel.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

When significantly changing the patch from one version to another,
(as in this case), you are supposed to drop the Reviewed-by tags.


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?


> ---
> Changes since v8:
> 
> - Add reviewer.
> 
> Changes since v4-v7:
> https://lore.kernel.org/linux-pci/20250102120222.1403906-1-18255117159@163.com/
> https://lore.kernel.org/linux-pci/20250101151509.570341-1-18255117159@163.com/
> 
> - Fix 32-bit OS warnings and errors.
> - Fix undefined reference to `__udivmoddi4`
> 
> Changes since v3:
> https://lore.kernel.org/linux-pci/20241221141009.27317-1-18255117159@163.com/
> 
> - The patch subject were modified.
> 
> Changes since v2:
> https://lore.kernel.org/linux-pci/20241220075253.16791-1-18255117159@163.com/
> 
> - Fix "changes" part goes below the --- line
> - The patch commit message were modified.
> 
> Changes since v1:
> https://lore.kernel.org/linux-pci/20241217121220.19676-1-18255117159@163.com/
> 
> - The patch subject and commit message were modified.
> ---
>  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;
>  
>  	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;
> +	}
>  	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
>