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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 v4 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW
Date: Fri, 2 Dec 2022 18:32:26 -0800	[thread overview]
Message-ID: <202212021832.3793DA082C@keescook> (raw)
In-Reply-To: <20221203003606.6838-13-rick.p.edgecombe@intel.com>

On Fri, Dec 02, 2022 at 04:35:39PM -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 reserved 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:
> 
> The first case is that 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.
> 
> The second case is that 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 disables based on runtime detection of the feature.
> 
> 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

  reply	other threads:[~2022-12-03  2:32 UTC|newest]

Thread overview: 107+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-03  0:35 [PATCH v4 00/39] Shadow stacks for userspace Rick Edgecombe
2022-12-03  0:35 ` [PATCH v4 01/39] Documentation/x86: Add CET shadow stack description Rick Edgecombe
2022-12-03  2:20   ` Kees Cook
2022-12-03  8:58   ` Bagas Sanjaya
2022-12-05 21:20     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 02/39] x86/shstk: Add Kconfig option for Shadow Stack Rick Edgecombe
2022-12-03  2:20   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks Rick Edgecombe
2022-12-03  2:22   ` Kees Cook
2022-12-07 11:00   ` Borislav Petkov
2022-12-07 22:35     ` Edgecombe, Rick P
2022-12-08 11:10       ` Borislav Petkov
2022-12-03  0:35 ` [PATCH v4 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack Rick Edgecombe
2022-12-03  2:23   ` Kees Cook
2022-12-07 12:49   ` Borislav Petkov
2022-12-07 18:35     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 05/39] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2022-12-03  2:24   ` Kees Cook
2022-12-20 11:32   ` Borislav Petkov
2022-12-21  0:45     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 06/39] x86/fpu: Add helper for modifying xstate Rick Edgecombe
2022-12-03  2:25   ` Kees Cook
2022-12-20 12:04   ` Borislav Petkov
2022-12-21  0:03     ` Edgecombe, Rick P
2022-12-21 10:31       ` Borislav Petkov
2022-12-03  0:35 ` [PATCH v4 07/39] x86: Add user control-protection fault handler Rick Edgecombe
2022-12-03  2:28   ` Kees Cook
2022-12-20 16:19   ` Borislav Petkov
2022-12-21  0:37     ` Edgecombe, Rick P
2022-12-21 10:41       ` Borislav Petkov
2022-12-21 21:42         ` Edgecombe, Rick P
2023-01-04 12:50           ` Borislav Petkov
2022-12-20 21:21   ` Borislav Petkov
2022-12-21  0:38     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 08/39] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2022-12-03  2:29   ` Kees Cook
2022-12-20 19:11   ` Borislav Petkov
2022-12-03  0:35 ` [PATCH v4 09/39] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2022-12-03  0:35 ` [PATCH v4 10/39] x86/mm: Introduce _PAGE_COW Rick Edgecombe
2022-12-03  2:31   ` Kees Cook
2022-12-20 21:29   ` Borislav Petkov
2022-12-21  0:45     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 11/39] x86/mm: Update pte_modify for _PAGE_COW Rick Edgecombe
2022-12-03  2:31   ` Kees Cook
2022-12-27 11:42   ` Borislav Petkov
2022-12-27 23:31     ` Edgecombe, Rick P
2023-01-04 13:25       ` Borislav Petkov
2023-01-05  1:06         ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Rick Edgecombe
2022-12-03  2:32   ` Kees Cook [this message]
2022-12-27 13:26   ` Borislav Petkov
2022-12-27 22:26     ` Edgecombe, Rick P
2023-01-04 13:28       ` Borislav Petkov
2022-12-03  0:35 ` [PATCH v4 13/39] x86/mm: Start actually marking _PAGE_COW Rick Edgecombe
2022-12-03  2:33   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 14/39] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2022-12-03  0:35 ` [PATCH v4 15/39] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2022-12-03  2:34   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 16/39] x86/mm: Check Shadow Stack page fault errors Rick Edgecombe
2023-01-04 14:32   ` Borislav Petkov
2023-01-05  1:29     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 17/39] x86/mm: Update maybe_mkwrite() for shadow stack Rick Edgecombe
2022-12-03  2:34   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 18/39] mm: Fixup places that call pte_mkwrite() directly Rick Edgecombe
2022-12-03  2:37   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 19/39] mm: Add guard pages around a shadow stack Rick Edgecombe
2022-12-03  0:35 ` [PATCH v4 20/39] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2022-12-03  2:38   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 21/39] mm/mprotect: Exclude shadow stack from preserve_write Rick Edgecombe
2022-12-03  2:38   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 22/39] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2022-12-03  0:35 ` [PATCH v4 23/39] mm: Don't allow write GUPs to shadow stack memory Rick Edgecombe
2022-12-03  2:39   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 24/39] mm: Warn on shadow stack memory in wrong vma Rick Edgecombe
2022-12-03  2:40   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 25/39] x86: Introduce userspace API for shadow stack Rick Edgecombe
2022-12-03  2:42   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 26/39] x86/shstk: Add user-mode shadow stack support Rick Edgecombe
2022-12-03  2:43   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 27/39] x86/shstk: Handle thread shadow stack Rick Edgecombe
2022-12-03  2:44   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 28/39] x86/shstk: Introduce routines modifying shstk Rick Edgecombe
2022-12-03  2:45   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 29/39] x86/shstk: Handle signals for shadow stack Rick Edgecombe
2022-12-03  2:46   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 30/39] x86/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2022-12-03  2:51   ` Kees Cook
2022-12-05 22:19     ` Edgecombe, Rick P
2022-12-03  0:35 ` [PATCH v4 31/39] x86/shstk: Support wrss for userspace Rick Edgecombe
2022-12-03  2:52   ` Kees Cook
2022-12-03  0:35 ` [PATCH v4 32/39] x86: Expose thread features in /proc/$PID/status Rick Edgecombe
2022-12-03  2:52   ` Kees Cook
2022-12-03  0:36 ` [PATCH v4 33/39] x86: Prevent 32 bit operations for 64 bit shstk tasks Rick Edgecombe
2022-12-03 22:49   ` Andy Lutomirski
2022-12-04 20:51     ` Edgecombe, Rick P
2022-12-15  0:25       ` Edgecombe, Rick P
2022-12-03  0:36 ` [PATCH v4 34/39] x86/shstk: Wire in shadow stack interface Rick Edgecombe
2022-12-03  0:36 ` [PATCH v4 35/39] selftests/x86: Add shadow stack test Rick Edgecombe
2022-12-03  0:36 ` [PATCH v4 36/39] x86/fpu: Add helper for initing features Rick Edgecombe
2022-12-03  0:36 ` [PATCH v4 37/39] x86: Add PTRACE interface for shadow stack Rick Edgecombe
2022-12-03  2:55   ` Kees Cook
2022-12-09 17:04   ` Mike Rapoport
2022-12-09 17:08     ` Edgecombe, Rick P
2022-12-03  0:36 ` [PATCH v4 38/39] x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe
2022-12-03  2:56   ` Kees Cook
2022-12-03  0:36 ` [PATCH v4 39/39] x86/shstk: Add ARCH_SHSTK_STATUS Rick Edgecombe
2022-12-03  2:57   ` Kees Cook

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