From: Kees Cook <keescook@chromium.org>
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
Weijiang Yang <weijiang.yang@intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
John Allen <john.allen@amd.com>,
kcc@google.com, eranian@google.com, rppt@kernel.org,
jamorris@linux.microsoft.com, dethoma@microsoft.com,
akpm@linux-foundation.org, Andrew.Cooper3@citrix.com,
christina.schimpe@intel.com, Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: Re: [PATCH v5 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW
Date: Thu, 19 Jan 2023 16:58:53 -0800 [thread overview]
Message-ID: <202301191658.A599D620B@keescook> (raw)
In-Reply-To: <20230119212317.8324-13-rick.p.edgecombe@intel.com>
On Thu, Jan 19, 2023 at 01:22:50PM -0800, Rick Edgecombe wrote:
> From: Yu-cheng Yu <yu-cheng.yu@intel.com>
>
> When shadow stack is in use, Write=0,Dirty=1 PTE are preserved for
> shadow stack. Copy-on-write PTEs then have Write=0,Cow=1.
>
> When a PTE goes from Write=1,Dirty=1 to Write=0,Cow=1, it could
> become a transient shadow stack PTE in two cases:
>
> 1. Some processors can start a write but end up seeing a Write=0 PTE by
> the time they get to the Dirty bit, creating a transient shadow stack
> PTE. However, this will not occur on processors supporting shadow
> stack, and a TLB flush is not necessary.
>
> 2. When _PAGE_DIRTY is replaced with _PAGE_COW non-atomically, a transient
> shadow stack PTE can be created as a result. Thus, prevent that with
> cmpxchg.
>
> In the case of pmdp_set_wrprotect(), for nopmd configs the ->pmd operated
> on does not exist and the logic would need to be different. Although the
> extra functionality will normally be optimized out when user shadow
> stacks are not configured, also exclude it in the preprocessor stage so
> that it will still compile. User shadow stack is not supported there by
> Linux anyway. Leave the cpu_feature_enabled() check so that the
> functionality also gets disabled based on runtime detection of the
> feature.
>
> Similarly, compile it out in ptep_set_wrprotect() due to a clang warning
> on i386. Like above, the code path should get optimized out on i386
> since shadow stack is not supported on 32 bit kernels, but this makes
> the compiler happy.
>
> Dave Hansen, Jann Horn, Andy Lutomirski, and Peter Zijlstra provided many
> insights to the issue. Jann Horn provided the cmpxchg solution.
>
> Tested-by: Pengfei Xu <pengfei.xu@intel.com>
> Tested-by: John Allen <john.allen@amd.com>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2023-01-20 0:59 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-19 21:22 [PATCH v5 00/39] Shadow stacks for userspace Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 01/39] Documentation/x86: Add CET shadow stack description Rick Edgecombe
2023-01-20 0:38 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 02/39] x86/shstk: Add Kconfig option for shadow stack Rick Edgecombe
2023-01-20 0:40 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks Rick Edgecombe
2023-01-20 0:44 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack Rick Edgecombe
2023-01-20 0:46 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 05/39] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2023-01-20 0:46 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 06/39] x86/fpu: Add helper for modifying xstate Rick Edgecombe
2023-01-20 0:47 ` Kees Cook
2023-02-01 11:01 ` Borislav Petkov
2023-02-01 17:31 ` Edgecombe, Rick P
2023-02-01 18:18 ` Borislav Petkov
2023-01-19 21:22 ` [PATCH v5 07/39] x86: Add user control-protection fault handler Rick Edgecombe
2023-01-20 0:50 ` Kees Cook
2023-02-03 19:09 ` Borislav Petkov
2023-02-03 19:24 ` Edgecombe, Rick P
2023-02-03 19:44 ` Borislav Petkov
2023-02-03 23:01 ` Edgecombe, Rick P
2023-02-04 10:37 ` Borislav Petkov
2023-01-19 21:22 ` [PATCH v5 08/39] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2023-01-20 0:52 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 09/39] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 10/39] x86/mm: Introduce _PAGE_COW Rick Edgecombe
2023-01-20 0:55 ` Kees Cook
2023-01-23 9:16 ` David Hildenbrand
2023-01-23 9:28 ` David Hildenbrand
2023-01-23 20:56 ` Edgecombe, Rick P
2023-01-24 16:28 ` David Hildenbrand
2023-01-19 21:22 ` [PATCH v5 11/39] x86/mm: Update pte_modify for _PAGE_COW Rick Edgecombe
2023-01-20 0:57 ` Kees Cook
2023-02-09 14:08 ` Borislav Petkov
2023-02-09 17:09 ` Edgecombe, Rick P
2023-02-10 13:57 ` Borislav Petkov
2023-02-10 17:00 ` Edgecombe, Rick P
2023-02-17 16:11 ` Borislav Petkov
2023-02-17 16:53 ` Edgecombe, Rick P
2023-01-19 21:22 ` [PATCH v5 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Rick Edgecombe
2023-01-20 0:58 ` Kees Cook [this message]
2023-01-19 21:22 ` [PATCH v5 13/39] x86/mm: Start actually marking _PAGE_COW Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 14/39] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 15/39] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 16/39] x86/mm: Check shadow stack page fault errors Rick Edgecombe
2023-01-20 0:59 ` Kees Cook
2023-01-19 21:22 ` [PATCH v5 17/39] x86/mm: Update maybe_mkwrite() for shadow stack Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk Rick Edgecombe
2023-01-23 9:50 ` David Hildenbrand
2023-01-23 20:47 ` Edgecombe, Rick P
2023-01-24 16:24 ` David Hildenbrand
2023-01-24 18:14 ` Edgecombe, Rick P
2023-01-25 9:27 ` David Hildenbrand
2023-01-25 18:43 ` Edgecombe, Rick P
2023-01-26 0:59 ` Edgecombe, Rick P
2023-01-26 8:46 ` David Hildenbrand
2023-01-26 20:19 ` Edgecombe, Rick P
2023-01-27 16:12 ` David Hildenbrand
2023-01-28 0:51 ` Edgecombe, Rick P
2023-01-31 8:46 ` David Hildenbrand
2023-01-31 23:33 ` Edgecombe, Rick P
2023-02-01 9:03 ` David Hildenbrand
2023-02-01 17:32 ` Edgecombe, Rick P
2023-02-01 18:03 ` David Hildenbrand
2023-01-26 8:57 ` David Hildenbrand
2023-01-26 20:16 ` Edgecombe, Rick P
2023-01-27 16:19 ` David Hildenbrand
2023-01-19 21:22 ` [PATCH v5 19/39] mm: Fixup places that call pte_mkwrite() directly Rick Edgecombe
2023-01-20 1:01 ` Kees Cook
2023-02-14 0:09 ` Deepak Gupta
2023-02-14 1:07 ` Edgecombe, Rick P
2023-02-14 6:10 ` Deepak Gupta
2023-02-14 18:24 ` Edgecombe, Rick P
2023-02-15 6:37 ` Deepak Gupta
2023-01-19 21:22 ` [PATCH v5 20/39] mm: Add guard pages around a shadow stack Rick Edgecombe
2023-01-19 21:22 ` [PATCH v5 21/39] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 22/39] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory Rick Edgecombe
2023-01-23 9:10 ` David Hildenbrand
2023-01-23 10:45 ` Florian Weimer
2023-01-23 20:46 ` Edgecombe, Rick P
2023-01-24 16:26 ` David Hildenbrand
2023-01-24 18:42 ` Edgecombe, Rick P
2023-01-24 23:08 ` Kees Cook
2023-01-24 23:41 ` Edgecombe, Rick P
2023-01-25 9:29 ` David Hildenbrand
2023-01-25 15:23 ` Kees Cook
2023-01-25 15:36 ` Schimpe, Christina
2023-01-25 16:43 ` Schimpe, Christina
2023-01-19 21:23 ` [PATCH v5 24/39] x86/mm: Introduce MAP_ABOVE4G Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 25/39] mm: Warn on shadow stack memory in wrong vma Rick Edgecombe
2023-01-20 1:01 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 26/39] x86: Introduce userspace API for shadow stack Rick Edgecombe
2023-01-20 1:04 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 27/39] x86/shstk: Add user-mode shadow stack support Rick Edgecombe
2023-01-20 1:05 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 28/39] x86/shstk: Handle thread shadow stack Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 29/39] x86/shstk: Introduce routines modifying shstk Rick Edgecombe
2023-01-20 1:05 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 30/39] x86/shstk: Handle signals for shadow stack Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 31/39] x86/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2023-01-20 1:07 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 32/39] x86/shstk: Support WRSS for userspace Rick Edgecombe
2023-01-20 1:06 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 33/39] x86: Expose thread features in /proc/$PID/status Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 34/39] x86/shstk: Wire in shadow stack interface Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 35/39] selftests/x86: Add shadow stack test Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 36/39] x86/fpu: Add helper for initing features Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 37/39] x86: Add PTRACE interface for shadow stack Rick Edgecombe
2023-01-20 1:08 ` Kees Cook
2023-01-19 21:23 ` [PATCH v5 38/39] x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe
2023-01-19 21:23 ` [PATCH v5 39/39] x86/shstk: Add ARCH_SHSTK_STATUS Rick Edgecombe
2023-01-20 1:08 ` Kees Cook
2023-01-19 22:26 ` [PATCH v5 00/39] Shadow stacks for userspace Andrew Morton
2023-01-20 17:27 ` Edgecombe, Rick P
2023-01-20 19:19 ` Kees Cook
2023-01-25 19:46 ` Edgecombe, Rick P
2023-01-20 17:48 ` John Allen
2023-01-22 8:20 ` Mike Rapoport
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