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Tue, 09 Jul 2024 14:09:35 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFUIpwg0q5tX/615i6NZ/zZJubSifIfLGh41ui/wVdDDxeaKO6CBzN2Bumt/d0xd4q/gI7xDw== X-Received: by 2002:a05:6a20:a111:b0:1c0:e925:f3e1 with SMTP id adf61e73a8af0-1c2984c9de7mr4305537637.50.1720559374128; Tue, 09 Jul 2024 14:09:34 -0700 (PDT) Received: from [172.31.79.51] ([216.9.110.4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70b438c70a4sm2290324b3a.83.2024.07.09.14.09.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jul 2024 14:09:33 -0700 (PDT) Message-ID: <0dc45181-de7e-4d97-9178-573c6f683f55@redhat.com> Date: Tue, 9 Jul 2024 23:09:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 7/8] mm: secretmem: use AS_INACCESSIBLE to prohibit GUP To: Patrick Roy , seanjc@google.com, pbonzini@redhat.com, akpm@linux-foundation.org, dwmw@amazon.co.uk, rppt@kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, willy@infradead.org, graf@amazon.com, derekmn@amazon.com, kalyazin@amazon.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, dmatlack@google.com, tabba@google.com, chao.p.peng@linux.intel.com, xmarcalx@amazon.co.uk References: <20240709132041.3625501-1-roypat@amazon.co.uk> <20240709132041.3625501-8-roypat@amazon.co.uk> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E5E1240016 X-Stat-Signature: n5kpwfhj59gwm5xb9ogkxgaoc8i3z6ru X-Rspam-User: X-HE-Tag: 1720559379-861996 X-HE-Meta: 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 r4bbvDuo D53QWyMG3RPLf+cTXKdMTnlWudNX6HJ6cliFBuOo0HKkzwkZzfhLzfBfJznRgK7Qxc6ae5NtG7CcSSjFO3iflwnwVqjXMU37tYcKMVqYZXsezdqlGMYZBtlUknO6ku8ToPoc8bTv95TrHa7iPpQh1G8aHRrOyNHrx2CEjURFSAVT5WFjtHnUWJ2eVHSR47IJMOG/hVFUcnt1II4FVCoLkif5cdVijpK6Yi/+SfRCS9Hj7S+skqL0YqOP5TfgOmkkGaygifqc2ptsSyCqO5f3a4cvnkwedLKkhKaENtN3v/VMUiiZk9YP1CLd3jVaQmUP5d4nyIUd9XOQEfP5/dmaymks6q7feWa966HTmSLWj+bkhTTkn6hiXJuJ86bipwq43NtBdpjM0uVrpaTjQmseR219lOnllZVLwSVdOvYq9DFBS0Zj0xh8V5bH7mCwdyIQ0YnD/BvUNLj/g11E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09.07.24 15:20, Patrick Roy wrote: > Inside of vma_is_secretmem and secretmem_mapping, instead of checking > whether a vm_area_struct/address_space has the secretmem ops structure > attached to it, check whether the address_space has the AS_INACCESSIBLE > bit set. Then set the AS_INACCESSIBLE flag for secretmem's > address_space. > > This means that get_user_pages and friends are disables for all > adress_spaces that set AS_INACCESIBLE. The AS_INACCESSIBLE flag was > introduced in commit c72ceafbd12c ("mm: Introduce AS_INACCESSIBLE for > encrypted/confidential memory") specifically for guest_memfd to indicate > that no reads and writes should ever be done to guest_memfd > address_spaces. Disallowing gup seems like a reasonable semantic > extension, and means that potential future mmaps of guest_memfd cannot > be GUP'd. > > Signed-off-by: Patrick Roy > --- > include/linux/secretmem.h | 13 +++++++++++-- > mm/secretmem.c | 6 +----- > 2 files changed, 12 insertions(+), 7 deletions(-) > > diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h > index e918f96881f5..886c8f7eb63e 100644 > --- a/include/linux/secretmem.h > +++ b/include/linux/secretmem.h > @@ -8,10 +8,19 @@ extern const struct address_space_operations secretmem_aops; > > static inline bool secretmem_mapping(struct address_space *mapping) > { > - return mapping->a_ops == &secretmem_aops; > + return mapping->flags & AS_INACCESSIBLE; > +} > + > +static inline bool vma_is_secretmem(struct vm_area_struct *vma) > +{ > + struct file *file = vma->vm_file; > + > + if (!file) > + return false; > + > + return secretmem_mapping(file->f_inode->i_mapping); > } That sounds wrong. You should leave *secretmem alone and instead have something like inaccessible_mapping that is used where appropriate. vma_is_secretmem() should not suddenly succeed on something that is not mm/secretmem.c -- Cheers, David / dhildenb