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

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Message-ID: <90939a1f-8519-4645-b869-5c1f8e701a3c@collabora.com>
Date: Fri, 15 Dec 2023 12:56:08 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Muhammad Usama Anjum <usama.anjum@...labora.com>,
 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

Hi Andrew,

On 12/15/23 12:40 AM, Andrew Morton wrote:
> 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.
This was getting triggered on KernelCI regularly because of different
ulimit settings which wasn't multiple of the page_size. Find logs here:
https://linux.kernelci.org/test/plan/id/657654bd8e81e654fae13532/ The bug
in was present from the time test was first added.
> 
>> 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:.
I was looking for email report from KernelCI. But I didn't find it. Not
sure if we can do something like following:
Closes: https://linux.kernelci.org/test/plan/id/657654bd8e81e654fae13532/

> 
> 

-- 
BR,
Muhammad Usama Anjum