From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Yu-cheng Yu <yu-cheng.yu@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>,
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>,
Haitao Huang <haitao.huang@intel.com>
Subject: Re: [PATCH v23 14/28] x86/mm: Shadow Stack page fault error checking
Date: Mon, 22 Mar 2021 13:38:58 +0300 [thread overview]
Message-ID: <20210322103858.evxun5bhw2i5sio6@box> (raw)
In-Reply-To: <20210316151054.5405-15-yu-cheng.yu@intel.com>
On Tue, Mar 16, 2021 at 08:10:40AM -0700, Yu-cheng Yu wrote:
> Shadow stack accesses are those that are performed by the CPU where it
> expects to encounter a shadow stack mapping. These accesses are performed
> implicitly by CALL/RET at the site of the shadow stack pointer. These
> accesses are made explicitly by shadow stack management instructions like
> WRUSSQ.
>
> Shadow stacks accesses to shadow-stack mapping can see faults in normal,
> valid operation just like regular accesses to regular mappings. Shadow
> stacks need some of the same features like delayed allocation, swap and
> copy-on-write.
>
> Shadow stack accesses can also result in errors, such as when a shadow
> stack overflows, or if a shadow stack access occurs to a non-shadow-stack
> mapping.
>
> In handling a shadow stack page fault, verify it occurs within a shadow
> stack mapping. It is always an error otherwise. For valid shadow stack
> accesses, set FAULT_FLAG_WRITE to effect copy-on-write. Because clearing
> _PAGE_DIRTY (vs. _PAGE_RW) is used to trigger the fault, shadow stack read
> fault and shadow stack write fault are not differentiated and both are
> handled as a write access.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
> arch/x86/include/asm/trap_pf.h | 2 ++
> arch/x86/mm/fault.c | 19 +++++++++++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/arch/x86/include/asm/trap_pf.h b/arch/x86/include/asm/trap_pf.h
> index 10b1de500ab1..afa524325e55 100644
> --- a/arch/x86/include/asm/trap_pf.h
> +++ b/arch/x86/include/asm/trap_pf.h
> @@ -11,6 +11,7 @@
> * bit 3 == 1: use of reserved bit detected
> * bit 4 == 1: fault was an instruction fetch
> * bit 5 == 1: protection keys block access
> + * bit 6 == 1: shadow stack access fault
> * bit 15 == 1: SGX MMU page-fault
> */
> enum x86_pf_error_code {
> @@ -20,6 +21,7 @@ enum x86_pf_error_code {
> X86_PF_RSVD = 1 << 3,
> X86_PF_INSTR = 1 << 4,
> X86_PF_PK = 1 << 5,
> + X86_PF_SHSTK = 1 << 6,
> X86_PF_SGX = 1 << 15,
> };
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index a73347e2cdfc..4316732a18c6 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1100,6 +1100,17 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
> (error_code & X86_PF_INSTR), foreign))
> return 1;
>
> + /*
> + * Verify a shadow stack access is within a shadow stack VMA.
> + * It is always an error otherwise. Normal data access to a
> + * shadow stack area is checked in the case followed.
> + */
> + if (error_code & X86_PF_SHSTK) {
> + if (!(vma->vm_flags & VM_SHSTK))
> + return 1;
> + return 0;
Any reason to return 0 here? I would rather keep the single return 0 in
the function, after all checks are done.
> + }
> +
> if (error_code & X86_PF_WRITE) {
> /* write, present and write, not present: */
> if (unlikely(!(vma->vm_flags & VM_WRITE)))
> @@ -1293,6 +1304,14 @@ void do_user_addr_fault(struct pt_regs *regs,
>
> perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
>
> + /*
> + * Clearing _PAGE_DIRTY is used to detect shadow stack access.
> + * This method cannot distinguish shadow stack read vs. write.
> + * For valid shadow stack accesses, set FAULT_FLAG_WRITE to effect
> + * copy-on-write.
> + */
> + if (error_code & X86_PF_SHSTK)
> + flags |= FAULT_FLAG_WRITE;
> if (error_code & X86_PF_WRITE)
> flags |= FAULT_FLAG_WRITE;
> if (error_code & X86_PF_INSTR)
> --
> 2.21.0
>
--
Kirill A. Shutemov
next prev parent reply other threads:[~2021-03-22 10:38 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 15:10 [PATCH v23 00/28] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 01/28] Documentation/x86: Add CET description Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 02/28] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 03/28] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 04/28] x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 05/28] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 06/28] x86/cet: Add control-protection fault handler Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 07/28] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Yu-cheng Yu
2021-03-22 9:13 ` Kirill A. Shutemov
2021-03-22 14:52 ` Yu, Yu-cheng
2021-03-16 15:10 ` [PATCH v23 08/28] x86/mm: Move pmd_write(), pud_write() up in the file Yu-cheng Yu
2021-03-22 11:28 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 09/28] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2021-03-22 11:29 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 10/28] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2021-03-22 11:30 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 11/28] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2021-03-22 11:31 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 12/28] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Yu-cheng Yu
2021-03-22 10:15 ` Kirill A. Shutemov
2021-03-22 10:46 ` Peter Zijlstra
2021-03-22 11:38 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 13/28] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2021-03-22 11:33 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 14/28] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2021-03-22 10:38 ` Kirill A. Shutemov [this message]
2021-03-22 17:27 ` Yu, Yu-cheng
2021-03-16 15:10 ` [PATCH v23 15/28] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2021-03-17 15:56 ` Borislav Petkov
2021-03-22 10:46 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 16/28] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2021-03-18 9:47 ` Borislav Petkov
2021-03-18 11:16 ` Borislav Petkov
2021-03-16 15:10 ` [PATCH v23 17/28] mm: Add guard pages around a shadow stack Yu-cheng Yu
2021-03-22 10:55 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 18/28] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2021-03-22 10:57 ` Kirill A. Shutemov
2021-03-26 15:46 ` Yu, Yu-cheng
2021-03-29 10:10 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 19/28] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 20/28] mm/mprotect: Exclude shadow stack from preserve_write Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 21/28] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2021-03-18 11:42 ` Borislav Petkov
2021-03-18 15:59 ` Yu, Yu-cheng
2021-03-18 16:13 ` Borislav Petkov
2021-03-16 15:10 ` [PATCH v23 22/28] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2021-03-18 12:32 ` Borislav Petkov
2021-03-18 19:05 ` Yu, Yu-cheng
2021-03-19 9:28 ` Borislav Petkov
2021-03-19 15:15 ` Yu, Yu-cheng
2021-03-16 15:10 ` [PATCH v23 23/28] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2021-03-19 12:51 ` Borislav Petkov
2021-03-16 15:10 ` [PATCH v23 24/28] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 25/28] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 26/28] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 27/28] mm: Move arch_calc_vm_prot_bits() to arch/x86/include/asm/mman.h Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 28/28] mm: Introduce PROT_SHSTK for shadow stack Yu-cheng Yu
2021-03-22 11:27 ` Kirill A. Shutemov
2021-03-16 21:15 ` [PATCH v23 00/28] Control-flow Enforcement: Shadow Stack Peter Zijlstra
2021-03-16 21:34 ` Yu, Yu-cheng
2021-03-17 9:18 ` Ingo Molnar
2021-03-17 10:14 ` Peter Zijlstra
2021-03-19 16:24 ` Yu, Yu-cheng
2021-03-19 21:43 ` Yu, Yu-cheng
2021-03-23 20:49 ` Peter Zijlstra
2021-03-23 21:03 ` Yu, Yu-cheng
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