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Message-ID: <544138c0-5668-4a6b-9160-59da95b990f6@lucifer.local>
Date: Wed, 5 Mar 2025 05:57:19 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
torvalds@...ux-foundation.org, vbabka@...e.cz, Liam.Howlett@...cle.com,
adhemerval.zanella@...aro.org, oleg@...hat.com, avagin@...il.com,
benjamin@...solutions.net, linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org, linux-mm@...ck.org,
linux-kselftest@...r.kernel.org, jorgelo@...omium.org,
sroettger@...gle.com, hch@....de, ojeda@...nel.org,
thomas.weissschuh@...utronix.de, adobriyan@...il.com,
johannes@...solutions.net, pedro.falcato@...il.com, hca@...ux.ibm.com,
willy@...radead.org, anna-maria@...utronix.de, mark.rutland@....com,
linus.walleij@...aro.org, Jason@...c4.com, deller@....de,
rdunlap@...radead.org, davem@...emloft.net, peterx@...hat.com,
f.fainelli@...il.com, gerg@...nel.org, dave.hansen@...ux.intel.com,
mingo@...nel.org, ardb@...nel.org, mhocko@...e.com,
42.hyeyoo@...il.com, peterz@...radead.org, ardb@...gle.com,
enh@...gle.com, rientjes@...gle.com, groeck@...omium.org,
mpe@...erman.id.au, aleksandr.mikhalitsyn@...onical.com,
mike.rapoport@...il.com, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v9 1/7] mseal sysmap: kernel config and header change
On Wed, Mar 05, 2025 at 05:54:24AM +0000, Lorenzo Stoakes wrote:
> On Wed, Mar 05, 2025 at 02:17:05AM +0000, jeffxu@...omium.org wrote:
> > From: Jeff Xu <jeffxu@...omium.org>
> >
> > 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@...omium.org>
> > Reviewed-by: Kees Cook <kees@...nel.org>
>
> 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@...cle.com>
>
(you also forgot to propagate Liam's tag here)
> > ---
> > 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
> >
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