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

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Message-ID: <abf72717-f0ca-4180-9e6f-83908581cbc1@amd.com>
Date: Thu, 19 Jun 2025 15:23:52 +0530
From: Shivank Garg <shivankg@....com>
To: Vlastimil Babka <vbabka@...e.cz>, 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, 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] fs: export anon_inode_make_secure_inode() and fix
 secretmem LSM bypass



On 6/19/2025 2:43 PM, Vlastimil Babka wrote:
> On 6/19/25 09:31, 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
> 
> Could we use the new EXPORT_SYMBOL_GPL_FOR_MODULES() thingy to make this
> explicit for KVM?
> 

Thanks for the suggestion.
I wasn't aware of this earlier. I think it makes sense to use it now.

So, the code would look like this:

+EXPORT_SYMBOL_GPL_FOR_MODULES(anon_inode_make_secure_inode, "kvm");

which builds fine for me. I hope this is the correct usage.

Thanks,
Shivank