linux-kernel - Re: [PATCH hotfix 6.12 v2 4/8] mm: resolve faulty mmap

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: <0b64edb9-491e-4dcd-8dc1-d3c8a336a49b@suse.cz>
Date: Mon, 28 Oct 2024 22:00:05 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Mark Brown <broonie@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
 Jann Horn <jannh@...gle.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, Peter Xu <peterx@...hat.com>,
 linux-arm-kernel@...ts.infradead.org,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Aishwarya TCV <Aishwarya.TCV@....com>
Subject: Re: [PATCH hotfix 6.12 v2 4/8] mm: resolve faulty mmap_region() error
 path behaviour

On 10/28/24 21:22, Linus Torvalds wrote:
> On Mon, 28 Oct 2024 at 10:18, Lorenzo Stoakes
> <lorenzo.stoakes@...cle.com> wrote:
>>
>> I'm genuinely not opposed to a horrible, awful:
>>
>> #ifdef CONFIG_ARM64
>>         if (file && file->f_ops == shmem_file_operations)
>>                 vm_flags |= VM_MTE_ALLOWED;
>> #endif
>>
>> Early in the operation prior to the arch_validate_flags() check.
> 
> I would just put it inside the arm64 code itself.
> 
> IOW, get rid of the VM_MTE_ALLOWED flag entirely, and just make the
> arm64 arch_validate_flags() code do something like
> 
>         if (flags & VM_MTE) {
>                 if (file->f_ops != shmem_file_operations)
>                         return false;
>         }
> 
> and be done with it.

VM_MTE_ALLOWED is also set by arm64's arch_calc_vm_flag_bits():

        if (system_supports_mte() && (flags & MAP_ANONYMOUS))
                return VM_MTE_ALLOWED;

And there's also this in arch/arm64/include/asm/page.h

#define VM_DATA_DEFAULT_FLAGS     (VM_DATA_FLAGS_TSK_EXEC | VM_MTE_ALLOWED)

So it would need to all be considered in the validation if we wanted to
replace VM_MTE_ALLOWED completely?

> Considering that we only have that horrendous arch_validate_flags()
> for two architectures, and that they both just have magical special
> cases for MTE-like behavior, I do think that just making it be a hack
> inside those functions is the way to go.
> 
>               Linus