linux-kernel - Re: [RFC PATCH v2 1/2] mm/mremap: Fix uprobe anon page be overwritten when expanding vma during mremap

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Message-ID: <dba2601d-5e11-447c-946f-0717478f6ffa@huaweicloud.com>
Date: Wed, 28 May 2025 00:35:50 +0800
From: Pu Lehui <pulehui@...weicloud.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: mhiramat@...nel.org, peterz@...radead.org, akpm@...ux-foundation.org,
 Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, vbabka@...e.cz,
 jannh@...gle.com, pfalcato@...e.de, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, pulehui@...wei.com
Subject: Re: [RFC PATCH v2 1/2] mm/mremap: Fix uprobe anon page be overwritten
 when expanding vma during mremap



On 2025/5/27 23:30, Oleg Nesterov wrote:
> Not that this is really important, but the test-case looks broken,
> 
> On 05/27, Pu Lehui wrote:
>>
>> #define _GNU_SOURCE
>> #include <fcntl.h>
>> #include <unistd.h>
>> #include <syscall.h>
>> #include <sys/mman.h>
>> #include <linux/perf_event.h>
>>
>> int main(int argc, char *argv[])
>> {
>>      int fd = open(FNAME, O_RDWR|O_CREAT, 0600);
> 
> FNAME is not defined
> 
>>      struct perf_event_attr attr = {
>>          .type = 9,
> 
> Cough ;) Yes I too used perf_event_attr.type == 9 when I wrote another
> test-case. Because I am lazy and this is what I see in
> /sys/bus/event_source/devices/uprobe/type on my machine.
> 
> But me should not assume that perf_pmu_register(&perf_uprobe) -> idr_alloc()
> will return 9.
> 
>>      write(fd, "x", 1);
> 
> looks unnecessary.
> 
> Oleg.

Oops...Thanks Oleg, I think I should thoroughly verify it. Perhaps I 
shouldn't be working on patches so late at night.🥱