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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 Subject: [PATCH v21 12/26] mm: Introduce VM_SHSTK for shadow stack memory Date: Wed, 17 Feb 2021 14:27:16 -0800 Message-Id: <20210217222730.15819-13-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210217222730.15819-1-yu-cheng.yu@intel.com> References: <20210217222730.15819-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 X-Stat-Signature: w8zggxstozzfgdqgm7yubfipksgdtz38 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CEF9AC0001FA Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf03; identity=mailfrom; envelope-from=""; helo=mga18.intel.com; client-ip=134.134.136.126 X-HE-DKIM-Result: none/none X-HE-Tag: 1613600879-861687 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: A shadow stack PTE must be read-only and have _PAGE_DIRTY set. However, read-only and Dirty PTEs also exist for copy-on-write (COW) pages. These two cases are handled differently for page faults. Introduce VM_SHSTK to track shadow stack VMAs. Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook --- Documentation/filesystems/proc.rst | 1 + arch/x86/mm/mmap.c | 2 ++ fs/proc/task_mmu.c | 3 +++ include/linux/mm.h | 8 ++++++++ 4 files changed, 14 insertions(+) diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesyste= ms/proc.rst index 2fa69f710e2a..fc533bfb9391 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -549,6 +549,7 @@ encoded manner. The codes are the following: mg mergable advise flag bt arm64 BTI guarded page mt arm64 MTE allocation tags are enabled + ss shadow stack page =3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 Note that there is no guarantee that every flag and associated mnemonic = will diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index c90c20904a60..a22c6b6fc607 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -165,6 +165,8 @@ unsigned long get_mmap_base(int is_legacy) =20 const char *arch_vma_name(struct vm_area_struct *vma) { + if (vma->vm_flags & VM_SHSTK) + return "[shadow stack]"; return NULL; } =20 diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 602e3a52884d..59623dcd92bb 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -661,6 +661,9 @@ static void show_smap_vma_flags(struct seq_file *m, s= truct vm_area_struct *vma) [ilog2(VM_PKEY_BIT4)] =3D "", #endif #endif /* CONFIG_ARCH_HAS_PKEYS */ +#ifdef CONFIG_X86_CET + [ilog2(VM_SHSTK)] =3D "ss", +#endif }; size_t i; =20 diff --git a/include/linux/mm.h b/include/linux/mm.h index ecdf8a8cd6ae..7be5f8b874aa 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -312,11 +312,13 @@ extern unsigned int kobjsize(const void *objp); #define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures= */ #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures= */ #define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures= */ +#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures= */ #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) #define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4) +#define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5) #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ =20 #ifdef CONFIG_ARCH_HAS_PKEYS @@ -332,6 +334,12 @@ extern unsigned int kobjsize(const void *objp); #endif #endif /* CONFIG_ARCH_HAS_PKEYS */ =20 +#ifdef CONFIG_X86_CET +# define VM_SHSTK VM_HIGH_ARCH_5 +#else +# define VM_SHSTK VM_NONE +#endif + #if defined(CONFIG_X86) # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ #elif defined(CONFIG_PPC) --=20 2.21.0