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b=gaDdLIb2asilEsYwMYfxjQiXe/jKOTfX6mA6XGwmSm/Trndrk8Y/Zr+WauUC+xHYl zlodR4URQHujRikilL9PJWpYh20D8Z5dtvNEtfyJCO+NGPA9SZoZjVt/ICFnY38znP 7rGQVVjjx98NLb9jVEPakhrFX0pk/iYwnJm3opeXZ2MM2vbUCiFdZtpcNxgh5QKIs+ EmRap+tWsjTRiV433a8Go5joeXBkKeDnUR3LtH1WQMHWf1TSemnF862L1poQ/dhE5K n7w4E4JgfP7Iqbcqb21fEaTSzp6M6XM7c19v8Q2qX4s5T2BRiewwq+zWTeHG3llGfR eq7jxdjWOwP4w== Date: Wed, 10 Jul 2024 10:32:25 +0300 From: Mike Rapoport To: David Hildenbrand Cc: Patrick Roy , seanjc@google.com, pbonzini@redhat.com, akpm@linux-foundation.org, dwmw@amazon.co.uk, 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 Subject: Re: [RFC PATCH 7/8] mm: secretmem: use AS_INACCESSIBLE to prohibit GUP Message-ID: References: <20240709132041.3625501-1-roypat@amazon.co.uk> <20240709132041.3625501-8-roypat@amazon.co.uk> <0dc45181-de7e-4d97-9178-573c6f683f55@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0dc45181-de7e-4d97-9178-573c6f683f55@redhat.com> X-Stat-Signature: 7uyzoi7qk9xakkqotich6f5ub3h15yw5 X-Rspamd-Queue-Id: 85F3E2001D X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1720596912-926682 X-HE-Meta: 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 3D6aR1Zy HHa4OoG2Q4Z5LJl54C40VX+r/724r7f2G3+GZmlM0bh1koNg7+CWF/Ii4/7Vl3IrFv7PX1Nz/ODeV+R/JrEVLzT0Dc8gfYxa7b5jgDzm7zi6L3Zr8LKAdekNJoEMBAaVRpK0yX5v1pj9ZH6aP440Fam9GS2FPvGWROo2oRF77z2wEP2JOP7hyNiTtWGUO9oA+OcdZUOmHeooZT0BeGd7zX/E0r+BJCgm3fpKuL3ka4+ISb70BrAg+siQEPDMAGQQV3hTq7wgonJyHmyIk4e7K1BZEobOOrAdoT/8zTCFe3SZwScE= 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 Tue, Jul 09, 2024 at 11:09:29PM +0200, David Hildenbrand wrote: > 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 I'm with David here. > -- > Cheers, > > David / dhildenb > -- Sincerely yours, Mike.