Re: [PATCH v5 11/38] selinux: reject writable opens of policy file, drop mmap shared/write check

[David Hildenbrand (Arm)]

On 10/9/26 20:04, Lorenzo Stoakes (ARM) wrote:
> The policy file has no write method and is exposed read-only (S_IRUGO in
> selinux_files[]), yet sel_open_policy() performs no open mode check, so a
> CAP_DAC_OVERRIDE caller can open it O_RDWR. Reject FMODE_WRITE at open, as
> kernfs does.
> 
> The file can then never be mapped with FMODE_WRITE, so do_mmap() always
> clears VM_MAYWRITE and VM_SHARED for MAP_SHARED mappings and the VM_SHARED
> check in sel_mmap_policy() cannot be reached. Remove it.
> 
> This also stops sel_mmap_policy() clearing VM_MAYWRITE on a mapping that is
> neither a PFN map nor a mixed map, ahead of the core enforcing that only
> such mappings may do so.
> 
> Acked-by: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
> Reviewed-by: Jann Horn <jannh@xxxxxxxxxx>
> Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David