linux-hardening - Re: [PATCH v2][next] hwmon: (aspeed-pwm-tacho) Fix -Wstringop-overflow warning in aspeed_create_fan_tach

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Date: Wed, 15 Nov 2023 12:03:27 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Guenter Roeck <linux@...ck-us.net>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Jean Delvare <jdelvare@...e.com>, Joel Stanley <joel@....id.au>,
 Andrew Jeffery <andrew@...econstruct.com.au>, linux-hwmon@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] hwmon: (aspeed-pwm-tacho) Fix
 -Wstringop-overflow warning in aspeed_create_fan_tach_channel()



On 11/15/23 07:12, Guenter Roeck wrote:
> On Tue, Nov 14, 2023 at 01:53:08PM -0600, Gustavo A. R. Silva wrote:
>> Based on the documentation below, the maximum number of Fan tach
>> channels is 16:
>>
>> Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt:45:
>>   45 - aspeed,fan-tach-ch : should specify the Fan tach input channel.
>>   46                 integer value in the range 0 through 15, with 0 indicating
>>   47                 Fan tach channel 0 and 15 indicating Fan tach channel 15.
>>   48                 At least one Fan tach input channel is required.
>>
>> However, the compiler doesn't know that, and legitimaly warns about a potential
>> overwrite in array `u8 fan_tach_ch_source[16]` in `struct aspeed_pwm_tacho_data`,
>> in case `index` takes a value outside the boundaries of the array:
>>
> 
> Still messes the point. This isn't about "the compiler doesn't know that",
> it is a real bug which may result in out-of-bounds accesses.

Oh, I mentioned that in anticipation of people saying something in the tone of
'that's never going to happen.' :p

However, if this is a real bug, it should probably be tagged for -stable.

> 
> Oh, never mind, I'll just apply it.

Thank you!

--
Gustavo