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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <06bd94c0-fefe-4bdc-8483-2d9b6703c3d6@redhat.com>
Date: Mon, 26 May 2025 20:46:07 +0200
From: David Hildenbrand <david@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>, Pu Lehui <pulehui@...weicloud.com>
Cc: lorenzo.stoakes@...cle.com, mhiramat@...nel.org, peterz@...radead.org,
 Liam.Howlett@...cle.com, akpm@...ux-foundation.org, 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] mm/mmap: Fix uprobe anon page be overwritten when
 expanding vma during mremap

On 26.05.25 17:48, Oleg Nesterov wrote:
> Hi Lehui,
> 
> As I said, I don't understand mm/, so can't comment, but...
> 
> On 05/26, Pu Lehui wrote:
>>
>> To make things simpler, perhaps we could try post-processing, that is:
>>
>> diff --git a/mm/mremap.c b/mm/mremap.c
>> index 83e359754961..46a757fd26dc 100644
>> --- a/mm/mremap.c
>> +++ b/mm/mremap.c
>> @@ -240,6 +240,11 @@ static int move_ptes(struct pagetable_move_control
>> *pmc,
>>                  if (pte_none(ptep_get(old_pte)))
>>                          continue;
>>
>> +               /* skip move pte when expanded range has uprobe */
>> +               if (unlikely(pte_present(*new_pte) &&
>> +                            vma_has_uprobes(pmc->new, new_addr, new_addr +
>> PAGE_SIZE)))
>> +                       continue;
>> +
> 
> I was thinking about
> 
> 	WARN_ON(!pte_none(*new_pte))
> 
> at the start of the main loop.
> 
> Obviously not to fix the problem, but rather to make it more explicit.

Yeah, WARN_ON_ONCE().

We really should fix the code to not install uprobes into the area we 
are moving.

Likely, the correct fix will be to pass the range as well to 
uprobe_mmap(), and passing that range to build_probe_list().

Only when growing using mremap(), we want to call it on the extended 
range only.

-- 
Cheers,

David / dhildenb