linux-kernel - Re: [PATCH V2] fs: export anon_inode_make_secure

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: <3114d54f-ed7c-4c68-9d32-53ce04175556@amd.com>
Date: Mon, 23 Jun 2025 19:38:39 +0530
From: Shivank Garg <shivankg@....com>
To: David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
 brauner@...nel.org, paul@...l-moore.com, rppt@...nel.org,
 viro@...iv.linux.org.uk
Cc: seanjc@...gle.com, vbabka@...e.cz, willy@...radead.org,
 pbonzini@...hat.com, tabba@...gle.com, afranji@...gle.com,
 ackerleytng@...gle.com, jack@...e.cz, hch@...radead.org,
 cgzones@...glemail.com, ira.weiny@...el.com, roypat@...zon.co.uk,
 linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH V2] fs: export anon_inode_make_secure_inode() and fix
 secretmem LSM bypass



On 6/23/2025 7:21 PM, David Hildenbrand wrote:
> On 20.06.25 09:03, Shivank Garg wrote:
>> Export anon_inode_make_secure_inode() to allow KVM guest_memfd to create
>> anonymous inodes with proper security context. This replaces the current
>> pattern of calling alloc_anon_inode() followed by
>> inode_init_security_anon() for creating security context manually.
>>
>> This change also fixes a security regression in secretmem where the
>> S_PRIVATE flag was not cleared after alloc_anon_inode(), causing
>> LSM/SELinux checks to be bypassed for secretmem file descriptors.
>>
>> As guest_memfd currently resides in the KVM module, we need to export this
>> symbol for use outside the core kernel. In the future, guest_memfd might be
>> moved to core-mm, at which point the symbols no longer would have to be
>> exported. When/if that happens is still unclear.
>>
>> Fixes: 2bfe15c52612 ("mm: create security context for memfd_secret inodes")
>> Suggested-by: David Hildenbrand <david@...hat.com>
>> Suggested-by: Mike Rapoport <rppt@...nel.org>
>> Signed-off-by: Shivank Garg <shivankg@....com>
> 
> 
> In general, LGTM, but I think the actual fix should be separated from exporting it for guest_memfd purposes?
> 
> Also makes backporting easier, when EXPORT_SYMBOL_GPL_FOR_MODULES does not exist yet ...
> 
I agree. I did not think about backporting conflicts when sending the patch.

Christian, I can send it as 2 separate patches to make it easier?

Thanks,
Shivank