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From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: 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>,
	Kees Cook <keescook@chromium.org>,
	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>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v14 18/26] mm: Update can_follow_write_pte() for shadow stack
Date: Mon, 12 Oct 2020 08:38:42 -0700
Message-ID: <20201012153850.26996-19-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20201012153850.26996-1-yu-cheng.yu@intel.com>

Can_follow_write_pte() ensures a read-only page is COWed by checking the
FOLL_COW flag, and uses pte_dirty() to validate the flag is still valid.

Like a writable data page, a shadow stack page is writable, and becomes
read-only during copy-on-write, but it is always dirty.  Thus, in the
can_follow_write_pte() check, it belongs to the writable page case and
should be excluded from the read-only page pte_dirty() check.  Apply
the same changes to can_follow_write_pmd().

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
 mm/gup.c         | 8 +++++---
 mm/huge_memory.c | 8 +++++---
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index e869c634cc9a..10e32f574822 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -384,10 +384,12 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
  * FOLL_FORCE can write to even unwritable pte's, but only
  * after we've gone through a COW cycle and they are dirty.
  */
-static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
+static inline bool can_follow_write_pte(pte_t pte, unsigned int flags,
+					struct vm_area_struct *vma)
 {
 	return pte_write(pte) ||
-		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
+		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte) &&
+				  !arch_shadow_stack_mapping(vma->vm_flags));
 }
 
 static struct page *follow_page_pte(struct vm_area_struct *vma,
@@ -430,7 +432,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
 	}
 	if ((flags & FOLL_NUMA) && pte_protnone(pte))
 		goto no_page;
-	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
+	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags, vma)) {
 		pte_unmap_unlock(ptep, ptl);
 		return NULL;
 	}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 01252b00cd06..fd22ceaba945 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1324,10 +1324,12 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
  * FOLL_FORCE can write to even unwritable pmd's, but only
  * after we've gone through a COW cycle and they are dirty.
  */
-static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
+static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags,
+					struct vm_area_struct *vma)
 {
 	return pmd_write(pmd) ||
-	       ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
+	       ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd) &&
+				  !arch_shadow_stack_mapping(vma->vm_flags));
 }
 
 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
@@ -1340,7 +1342,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
 
 	assert_spin_locked(pmd_lockptr(mm, pmd));
 
-	if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
+	if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags, vma))
 		goto out;
 
 	/* Avoid dumping huge zero page */
-- 
2.21.0


  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 15:38 [PATCH v14 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 01/26] Documentation/x86: Add CET description Yu-cheng Yu
2020-11-06 17:34   ` Borislav Petkov
2020-11-06 18:16     ` Yu, Yu-cheng
2020-11-06 18:28       ` Borislav Petkov
2020-11-06 18:32         ` Yu, Yu-cheng
2020-10-12 15:38 ` [PATCH v14 02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-11-06 18:49   ` Borislav Petkov
2020-11-06 19:48     ` Yu, Yu-cheng
2020-11-06 20:11       ` Borislav Petkov
2020-11-06 20:14         ` Yu, Yu-cheng
2020-10-12 15:38 ` [PATCH v14 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-10-12 19:58   ` Cyrill Gorcunov
2020-10-12 20:48     ` Yu, Yu-cheng
2020-10-12 15:38 ` [PATCH v14 04/26] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 08/26] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 09/26] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 10/26] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 12/26] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 13/26] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 14/26] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 15/26] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 16/26] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 17/26] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-10-12 15:38 ` Yu-cheng Yu [this message]
2020-10-12 15:38 ` [PATCH v14 19/26] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 20/26] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 21/26] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 22/26] binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND properties Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 23/26] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 24/26] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 25/26] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 26/26] mm: Introduce PROT_SHSTK " Yu-cheng Yu
  -- strict thread matches above, loose matches on Subject: below --
2020-10-09 18:32 [PATCH v14 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 18/26] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu

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