linux-kernel - Re: [PATCH 5.10 000/286] 5.10.209-rc1 review

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Date: Fri, 26 Jan 2024 17:03:18 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org,
	patches@...ts.linux.dev, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, llvm@...ts.linux.dev,
	keescook@...omium.org, arei.gonglei@...wei.com, mst@...hat.com,
	jasowang@...hat.com, virtualization@...ts.linux.dev,
	linux-crypto@...r.kernel.org
Subject: Re: [PATCH 5.10 000/286] 5.10.209-rc1 review

On Fri, Jan 26, 2024 at 03:55:02PM -0800, Guenter Roeck wrote:
> Anyway, how did you find that ? Is there a magic trick to find the
> actual code causing the warning ? I am asking because we had seen
> similar warnings before, and it would help to know how to find the
> problematic code.

The easiest way I have found is figuring out what primitive is causing
the warning (memset, memcpy) then just commenting out the uses in the
particular file until the warning goes away. Sometimes it is quick like
in this case since there were only two instances of memcpy() in that
file but other cases it can definitely take time. There could be
potential issues with that approach if the problematic use is in a
header, at which point you could generate a preprocessed ('.i') file and
see where fortify_memcpy_chk() or fortify_memset_chk() come from in that
file.

Cheers,
Nathan