On Mon, Mar 3, 2025 at 8:37 AM Kees Cook <kees@xxxxxxxxxx> wrote: > > On Mon, Mar 03, 2025 at 05:09:15AM +0000, jeffxu@xxxxxxxxxxxx wrote: > > From: Jeff Xu <jeffxu@xxxxxxxxxxxx> > > > > Provide infrastructure to mseal system mappings. Establish > > two kernel configs (CONFIG_MSEAL_SYSTEM_MAPPINGS, > > ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS) and VM_SEALED_SYSMAP > > macro for future patches. > > > > Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx> > > --- > > include/linux/mm.h | 10 ++++++++++ > > init/Kconfig | 22 ++++++++++++++++++++++ > > security/Kconfig | 21 +++++++++++++++++++++ > > 3 files changed, 53 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 7b1068ddcbb7..8b800941678d 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -4155,4 +4155,14 @@ int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *st > > int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status); > > int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status); > > > > + > > +/* > > + * mseal of userspace process's system mappings. > > + */ > > +#ifdef CONFIG_MSEAL_SYSTEM_MAPPINGS > > +#define VM_SEALED_SYSMAP VM_SEALED > > +#else > > +#define VM_SEALED_SYSMAP VM_NONE > > +#endif > > + > > #endif /* _LINUX_MM_H */ > > diff --git a/init/Kconfig b/init/Kconfig > > index d0d021b3fa3b..c90dd8778993 100644 > > --- a/init/Kconfig > > +++ b/init/Kconfig > > @@ -1882,6 +1882,28 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS > > config ARCH_HAS_MEMBARRIER_SYNC_CORE > > bool > > > > +config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS > > + bool > > + help > > + Control MSEAL_SYSTEM_MAPPINGS access based on architecture. > > + > > + A 64-bit kernel is required for the memory sealing feature. > > + No specific hardware features from the CPU are needed. > > + > > + To enable this feature, the architecture needs to update their > > + special mappings calls to include the sealing flag and confirm > > + that it doesn't unmap/remap system mappings during the life > > + time of the process. The existence of this flag for an architecture > > + implies that it does not require the remapping of thest system > > typo nit: "the" instead of "thest" > > > + mappings during process lifetime, so sealing these mappings is safe > > + from a kernel perspective. > > + > > + After the architecture enables this, a distribution can set > > + CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature. > > + > > + For complete descriptions of memory sealing, please see > > + Documentation/userspace-api/mseal.rst > > + > > config HAVE_PERF_EVENTS > > bool > > help > > diff --git a/security/Kconfig b/security/Kconfig > > index f10dbf15c294..5311f4a6786c 100644 > > --- a/security/Kconfig > > +++ b/security/Kconfig > > @@ -51,6 +51,27 @@ config PROC_MEM_NO_FORCE > > > > endchoice > > > > +config MSEAL_SYSTEM_MAPPINGS > > + bool "mseal system mappings" > > + depends on 64BIT > > + depends on ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS > > + depends on !CHECKPOINT_RESTORE > > + help > > + Apply mseal on system mappings. > > + The system mappings includes vdso, vvar, vvar_vclock, > > + vectors (arm compact-mode), sigpage (arm compact-mode), uprobes. > > typo nits: "compat" instead of "compact". > Got it, I will change everywhere for this (mseal.rst, coverletter) > > + > > + A 64-bit kernel is required for the memory sealing feature. > > + No specific hardware features from the CPU are needed. > > + > > + WARNING: This feature breaks programs which rely on relocating > > + or unmapping system mappings. Known broken software at the time > > + of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore > > + this config can't be enabled universally. > > + > > + For complete descriptions of memory sealing, please see > > + Documentation/userspace-api/mseal.rst > > + > > config SECURITY > > bool "Enable different security models" > > depends on SYSFS > > -- > > 2.48.1.711.g2feabab25a-goog > > > > Perhaps akpm can fix these up directly instead of a v9 spin? > V9 is relatively easy for me. I probably need a good version for backporting to chromeOS/Android. If all goes well, I'll follow up with a V10 based on Thomas Weißschuh's vdso refactor branch [1] [2]. [1] https://lore.kernel.org/all/CABi2SkXwaJ=s3XqHKu1aFVfcacgxpQ5Ji1_BqaN+ch2i_RnA9Q@xxxxxxxxxxxxxx/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/log/?h=timers/vdso > But otherwise, yes, reads well to me: > > Reviewed-by: Kees Cook <kees@xxxxxxxxxx> > > -- > Kees Cook
