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Mon, 24 Feb 2025 10:44:17 -0800 (PST) MIME-Version: 1.0 References: <20250224174513.3600914-1-jeffxu@google.com> <20250224174513.3600914-2-jeffxu@google.com> <443992d7-f694-4e46-b120-545350a5d598@intel.com> In-Reply-To: <443992d7-f694-4e46-b120-545350a5d598@intel.com> From: Jeff Xu Date: Mon, 24 Feb 2025 10:44:07 -0800 X-Gm-Features: AWEUYZmHQiSO8llCjmhY8a1Y8Dk59_j8_WwL1SOLQEoLurxsiSGp7YKgCz-mRG0 Message-ID: Subject: Re: [PATCH v6 1/7] mseal, system mappings: kernel config and header change To: Dave Hansen Cc: akpm@linux-foundation.org, keescook@chromium.org, jannh@google.com, torvalds@linux-foundation.org, vbabka@suse.cz, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, adhemerval.zanella@linaro.org, oleg@redhat.com, avagin@gmail.com, benjamin@sipsolutions.net, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, jorgelo@chromium.org, sroettger@google.com, hch@lst.de, ojeda@kernel.org, thomas.weissschuh@linutronix.de, adobriyan@gmail.com, johannes@sipsolutions.net, pedro.falcato@gmail.com, hca@linux.ibm.com, willy@infradead.org, anna-maria@linutronix.de, mark.rutland@arm.com, linus.walleij@linaro.org, Jason@zx2c4.com, deller@gmx.de, rdunlap@infradead.org, davem@davemloft.net, peterx@redhat.com, f.fainelli@gmail.com, gerg@kernel.org, dave.hansen@linux.intel.com, mingo@kernel.org, ardb@kernel.org, mhocko@suse.com, 42.hyeyoo@gmail.com, peterz@infradead.org, ardb@google.com, enh@google.com, rientjes@google.com, groeck@chromium.org, mpe@ellerman.id.au, aleksandr.mikhalitsyn@canonical.com, mike.rapoport@gmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CCD6DC0009 X-Stat-Signature: k8bfmg99saioomohrx1oauo3k4bre3ub X-HE-Tag: 1740422658-420161 X-HE-Meta: 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 3zKN7KQ4 9xfM1fMdPI6sOWoZhHD4HtKEhn7rTX24q0jSAfgGvaoYTPM2leESSI+ZcmxZH3eqQ93NEfgeyWDjVlcWkQSgWqBL952Zqo+njwrz5rDWKLaCzVv6igXtiSN3VaPV6ofGxyz+U/XdTusIOyvREp5s6qMxxhp9akSM1Nd/JWsEynugU6mLt2iPis/mVyh0AZDxaMi9Uzq65KsGmXSz//zYFXRwx1ACiTc4FZgv+ffP7Pa2IoZeOcApSyGu8RaCRDu6ipciRmMAdCE6lmKjWG2cXXmsyBiA6ooyDV3lNfuOQ4TWEMNuUvDBhM56A+0B4g+H4rfod 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 Mon, Feb 24, 2025 at 10:21=E2=80=AFAM Dave Hansen wrote: > > On 2/24/25 09:45, jeffxu@chromium.org wrote: > > +/* > > + * mseal of userspace process's system mappings. > > + */ > > +#ifdef CONFIG_MSEAL_SYSTEM_MAPPINGS > > +#define MSEAL_SYSTEM_MAPPINGS_VM_FLAG VM_SEALED > > +#else > > +#define MSEAL_SYSTEM_MAPPINGS_VM_FLAG VM_NONE > > +#endif > > This ends up looking pretty wonky in practice: > > > + vm_flags =3D VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP; > > + vm_flags |=3D MSEAL_SYSTEM_MAPPINGS_VM_FLAG; > > because MSEAL_SYSTEM_MAPPINGS_VM_FLAG is so much different from the > other ones. > > Would it really hurt to have > > #ifdef CONFIG_64BIT > /* VM is sealed, in vm_flags */ > #define VM_SEALED _BITUL(63) > +#else > +#define VM_SEALED VM_NONE > #endif > > ? > VM_SEALED isn't defined in 32-bit systems, and mseal.c isn't part of the build. This is intentional. Any 32-bit code trying to use the sealing function or the VM_SEALED flag will immediately fail compilation. This makes it easier to identify incorrect usage. For example: Consider the case below in src/third_party/kernel/v6.6/fs/proc/task_mmu.c, #ifdef CONFIG_64BIT [ilog2(VM_SEALED)] =3D "sl", #endif Redefining VM_SEALED to VM_NONE for 32 bit won't detect the problem in case that "#ifdef CONFIG_64BIT" line is missing. Please note, this has been like this since the first version of mseal() RFC patch, and I prefer to keep it this way. Thanks -Jeff