linux-kernel - Re: [PATCH v2 1/3] PCI: Relaxed tail alignment should never increase min

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Message-ID: <0185a58e-9211-4c10-bcf2-bbf2f566323e@web.de>
Date: Thu, 21 Aug 2025 19:00:10 +0200
From: Markus Elfring <Markus.Elfring@....de>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: stable@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
 kernel-janitors@...r.kernel.org, Christian König
 <christian.koenig@....com>, D Scott Phillips <scott@...amperecomputing.com>,
 Krzysztof Wilczyński <kw@...ux.com>, Rio Liu <rio@....me>,
 Tudor Ambarus <tudor.ambarus@...aro.org>
Subject: Re: [PATCH v2 1/3] PCI: Relaxed tail alignment should never increase
 min_align

>> …
>> +++ b/drivers/pci/setup-bus.c
>> …
>> @@ -1261,8 +1263,9 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>  		if (bus->self && size1 &&
>>  		    !pbus_upstream_space_available(bus, mask | IORESOURCE_PREFETCH, type,
>>  						   size1, add_align)) {
>> -			min_align = 1ULL << (max_order + __ffs(SZ_1M));
>> -			min_align = max(min_align, win_align);
>> +			relaxed_align = 1ULL << (max_order + __ffs(SZ_1M));
>> +			relaxed_align = max(min_align, win_align);
>> …
>>
>> I wonder why a variable content would be overwritten here
>> without using the previous value.
>> https://cwe.mitre.org/data/definitions/563.html
…> This looks a very good catch. I think it too should have been:
> 
> relaxed_align = max(relaxed_align, win_align);
> 
> ...like in the other case.

Did any known source code analysis tools point such a questionable implementation detail out
for further development considerations?

Regards,
Markus