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Mon, 24 Feb 2025 11:42:42 -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> <3nxcy7zshqxmjia7y6cyajeoclcxizkrhhsitji5ujbafbvhlu@7hqs6uodor56> <202502241123.D398A24@keescook> In-Reply-To: <202502241123.D398A24@keescook> From: Jeff Xu Date: Mon, 24 Feb 2025 11:42:31 -0800 X-Gm-Features: AWEUYZnIh-aVK2V5D2Z7CSJGHhvBCNIiddlen5uSwHi2kaMpnPPFF88FSIikjiE Message-ID: Subject: Re: [PATCH v6 1/7] mseal, system mappings: kernel config and header change To: Kees Cook Cc: "Liam R. Howlett" , Dave Hansen , akpm@linux-foundation.org, jannh@google.com, torvalds@linux-foundation.org, vbabka@suse.cz, lorenzo.stoakes@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: ED09A1A0017 X-Stat-Signature: tzf1tij3w6kx4814dyzwa9sfcitmwdqo X-HE-Tag: 1740426162-386398 X-HE-Meta: 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 YDb/N5Uk UGuVzIXraxQAwViDgWz51Q18eYmdBofu/XVqWYFHG99/CIJ/8m6JokV+WIDZJEY9r8tzkQnfwrTF7psh6/ert6YDLtq9v0ECGFJnIU3ZWx5LtteYeC4EyXioIWgyhFHIUOdKjjrSVCtsfJkvmjq7uKEbVBRn2BB2rWDePBWDjg8uOeR+XWaf6SLJcOuZdvaNz4n1mc372GronDvewpQ7xzAdfHFdlH8j9jS1utXhP6iSq0eNjRaxZbBX/zFaIsALxJZCug9qH/DMPuQCOvSb+rJOeKy0ouC3u8D6Mni/yxOU0mdsjXmHvDAjOp1odBKmmRzYtDrTilcoNfwUex9oeMJ6vcALc2I69+5np7i2YqqDkM04= 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 11:25=E2=80=AFAM Kees Cook wrote: > > On Mon, Feb 24, 2025 at 11:10:22AM -0800, Jeff Xu wrote: > > On Mon, Feb 24, 2025 at 11:03=E2=80=AFAM Liam R. Howlett > > wrote: > > > > > > * Jeff Xu [250224 13:44]: > > > > 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_PFNM= AP; > > > > > > + vm_flags |=3D MSEAL_SYSTEM_MAPPINGS_VM_FLAG; > > > > > > > > > > because MSEAL_SYSTEM_MAPPINGS_VM_FLAG is so much different from t= he > > > > > 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 o= f > > > > 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. > > > > > > > > > > The reason that two #defines are needed is because you can have mseal > > > enabled while not sealing system mappings, so for this to be clean we > > > need two defines. > > > > > > However MSEAL_SYSTEM_MAPPINGS_VM_FLAG, is _way_ too long, in my opini= on. > > > Keeping with "VM_SEALED" I'd suggest "VM_SYSTEM_SEALED". > > > > > How about MSEAL_SYSTME_MAPPINGS as Kees suggested ? > > > > The VM_SYSTEM_SEALED doesn't have the MSEAL key or the MAPPING, so it > > might take longer for the new reader to understand what it is. > > I think to address Dave's concern, it should start with "VM_". We use > "SEAL" already with VM_SEALED, so the "M" in "MSEAL" may be redundant, > and to clarify the system mapping, how avout VM_SEAL_SYSMAP ? That > capture's, hopefully, Dave, Liam, and your thoughts about the naming? > Liam had a comment in the previous version, asking everything related with mseal() to have the MSEAL keyword, that is why KCONFIG change has MSEAL. How about VM_MSEAL_SYSMAP ? -Jeff > -- > Kees Cook