Re: [PATCH v9 1/7] mseal sysmap: kernel config and header change

[Jeff Xu]

On Tue, Mar 4, 2025 at 9:57 PM Lorenzo Stoakes
<lorenzo.stoakes@xxxxxxxxxx> wrote:
>
> On Wed, Mar 05, 2025 at 05:54:24AM +0000, Lorenzo Stoakes wrote:
> > On Wed, Mar 05, 2025 at 02:17:05AM +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>
> > > Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
> >
> > Umm... I reviewed this too? :) unless you made substantial changes here
> > (doesn't appear so), please do propagate tags for each revision :>)
> >
> > Anyway, FWIW:
> >
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> >
>
> (you also forgot to propagate Liam's tag here)
>
Sorry about that, I missed  "Reviewed-by" from you and Liam's from V8 [1] [2]
[1] https://lore.kernel.org/all/maamck3gjqjikefwlubtzg4ymaa6vh47hlxqqn4v23gqwl2tli@t372meccgycq/
[2] https://lore.kernel.org/all/0ea20f84-bd66-4180-aa04-0f66ce91bdf6@lucifer.local/

Thanks


> > > ---
> > >  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..7f67d8942a09 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 the system
> > > +     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..a914a02df27e 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 compat-mode), sigpage (arm compat-mode), uprobes.
> > > +
> > > +     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
> > >