linux-kernel - Re: [PATCH] selftests: secretmem: Floor the memory size to the multiple of page

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Date: Thu, 14 Dec 2023 11:40:56 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>, James
 Bottomley <James.Bottomley@...senPartnership.com>, kernel@...labora.com,
 "kernelci.org bot" <bot@...nelci.org>, linux-mm@...ck.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: secretmem: Floor the memory size to the
 multiple of page_size

On Thu, 14 Dec 2023 15:19:30 +0500 Muhammad Usama Anjum <usama.anjum@...labora.com> wrote:

> The "locked-in-memory size" limit per process can be non-multiple of
> page_size. The mmap() fails if we try to allocate locked-in-memory
> with same size as the allowed limit if it isn't multiple of the
> page_size because mmap() rounds off the memory size to be allocated
> to next multiple of page_size.
> 
> Fix this by flooring the length to be allocated with mmap() to the
> previous multiple of the page_size.

I'd like to understand how this was noticed, what the ongoing effect
might be, etc.  To help decide which kernel version(s) need the patch.

> Fixes: 76fe17ef588a ("secretmem: test: add basic selftest for memfd_secret(2)")
> Reported-by: "kernelci.org bot" <bot@...nelci.org>

Which is one of the reasons we're now placing a Closes: tag after a
Reported-by:.