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Peter Anvin" , Thomas Gleixner , Ingo Molnar , 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 , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang Cc: Yu-cheng Yu , "Kirill A . Shutemov" Subject: [PATCH v24 15/30] x86/mm: Update maybe_mkwrite() for shadow stack Date: Thu, 1 Apr 2021 15:10:49 -0700 Message-Id: <20210401221104.31584-16-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210401221104.31584-1-yu-cheng.yu@intel.com> References: <20210401221104.31584-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 11E6040002C8 X-Stat-Signature: jucr7kccpjznc9ybzceubsbiyi8icyha Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf02; identity=mailfrom; envelope-from=""; helo=mga03.intel.com; client-ip=134.134.136.65 X-HE-DKIM-Result: none/none X-HE-Tag: 1617315084-115855 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When serving a page fault, maybe_mkwrite() makes a PTE writable if its vm= a has VM_WRITE. A shadow stack vma has VM_SHADOW_STACK. Its PTEs have _PAGE_DIRTY, but n= ot _PAGE_WRITE. In fork(), _PAGE_DIRTY is cleared to cause copy-on-write, and in the page fault handler, _PAGE_DIRTY is restored and the shadow sta= ck page is writable again. Introduce an x86 version of maybe_mkwrite(), which sets proper PTE bits according to VM flags. Apply the same changes to maybe_pmd_mkwrite(). Signed-off-by: Yu-cheng Yu Cc: Kees Cook Cc: Kirill A. Shutemov --- v24: - Instead of doing arch_maybe_mkwrite(), overwrite maybe*_mkwrite() with = x86 versions. - Change VM_SHSTK to VM_SHADOW_STACK. arch/x86/include/asm/pgtable.h | 8 ++++++++ arch/x86/mm/pgtable.c | 20 ++++++++++++++++++++ include/linux/mm.h | 2 ++ mm/huge_memory.c | 2 ++ 4 files changed, 32 insertions(+) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtabl= e.h index 46d9394b884f..51cdf14488b7 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1686,6 +1686,14 @@ static inline bool arch_faults_on_old_pte(void) return false; } =20 +#define maybe_mkwrite maybe_mkwrite +extern pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma); + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#define maybe_pmd_mkwrite maybe_pmd_mkwrite +extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma); +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + #endif /* __ASSEMBLY__ */ =20 #endif /* _ASM_X86_PGTABLE_H */ diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index f6a9e2e36642..e778dbbef3d8 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -610,6 +610,26 @@ int pmdp_clear_flush_young(struct vm_area_struct *vm= a, } #endif =20 +pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) +{ + if (likely(vma->vm_flags & VM_WRITE)) + pte =3D pte_mkwrite(pte); + else if (likely(vma->vm_flags & VM_SHADOW_STACK)) + pte =3D pte_mkwrite_shstk(pte); + return pte; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) +{ + if (likely(vma->vm_flags & VM_WRITE)) + pmd =3D pmd_mkwrite(pmd); + else if (likely(vma->vm_flags & VM_SHADOW_STACK)) + pmd =3D pmd_mkwrite_shstk(pmd); + return pmd; +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + /** * reserve_top_address - reserves a hole in the top of kernel address sp= ace * @reserve - size of hole to reserve diff --git a/include/linux/mm.h b/include/linux/mm.h index 08282eb2f195..6ac9b3e9a865 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -993,12 +993,14 @@ void free_compound_page(struct page *page); * pte_mkwrite. But get_user_pages can cause write faults for mappings * that do not have writing enabled, when used by access_process_vm. */ +#ifndef maybe_mkwrite static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pte =3D pte_mkwrite(pte); return pte; } +#endif =20 vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page); void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long a= ddr); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ae907a9c2050..8203bd6ae4bd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -478,12 +478,14 @@ static int __init setup_transparent_hugepage(char *= str) } __setup("transparent_hugepage=3D", setup_transparent_hugepage); =20 +#ifndef maybe_pmd_mkwrite pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pmd =3D pmd_mkwrite(pmd); return pmd; } +#endif =20 #ifdef CONFIG_MEMCG static inline struct deferred_split *get_deferred_split_queue(struct pag= e *page) --=20 2.21.0