From patchwork Wed Jun 3 05:19:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Christopher M. Riedl" X-Patchwork-Id: 11584973 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 305FD90 for ; Wed, 3 Jun 2020 05:18:18 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 6E7D720678 for ; Wed, 3 Jun 2020 05:18:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E7D720678 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=informatik.wtf Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18911-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 29991 invoked by uid 550); 3 Jun 2020 05:17:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 29892 invoked from network); 3 Jun 2020 05:17:53 -0000 From: "Christopher M. Riedl" To: linuxppc-dev@lists.ozlabs.org, kernel-hardening@lists.openwall.com Subject: [PATCH 3/5] powerpc/lib: Use a temporary mm for code patching Date: Wed, 3 Jun 2020 00:19:10 -0500 Message-Id: <20200603051912.23296-4-cmr@informatik.wtf> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200603051912.23296-1-cmr@informatik.wtf> References: <20200603051912.23296-1-cmr@informatik.wtf> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Currently, code patching a STRICT_KERNEL_RWX exposes the temporary mappings to other CPUs. These mappings should be kept local to the CPU doing the patching. Use the pre-initialized temporary mm and patching address for this purpose. Also add a check after patching to ensure the patch succeeded. Use the KUAP functions on non-BOOKS3_64 platforms since the temporary mapping for patching uses a userspace address (to keep the mapping local). On BOOKS3_64 platforms hash does not implement KUAP and on radix the use of PAGE_KERNEL sets EAA[0] for the PTE which means the AMR (KUAP) protection is ignored (see PowerISA v3.0b, Fig, 35). Based on x86 implementation: commit b3fd8e83ada0 ("x86/alternatives: Use temporary mm for text poking") Signed-off-by: Christopher M. Riedl --- arch/powerpc/lib/code-patching.c | 148 ++++++++++++------------------- 1 file changed, 55 insertions(+), 93 deletions(-) diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 599114f63b44..df0765845204 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -20,6 +20,7 @@ #include #include #include +#include static int __patch_instruction(struct ppc_inst *exec_addr, struct ppc_inst instr, struct ppc_inst *patch_addr) @@ -78,101 +79,58 @@ void __init poking_init(void) pte_unmap_unlock(ptep, ptl); } -static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); - -static int text_area_cpu_up(unsigned int cpu) -{ - struct vm_struct *area; - - area = get_vm_area(PAGE_SIZE, VM_ALLOC); - if (!area) { - WARN_ONCE(1, "Failed to create text area for cpu %d\n", - cpu); - return -1; - } - this_cpu_write(text_poke_area, area); - - return 0; -} - -static int text_area_cpu_down(unsigned int cpu) -{ - free_vm_area(this_cpu_read(text_poke_area)); - return 0; -} - -/* - * Run as a late init call. This allows all the boot time patching to be done - * simply by patching the code, and then we're called here prior to - * mark_rodata_ro(), which happens after all init calls are run. Although - * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge - * it as being preferable to a kernel that will crash later when someone tries - * to use patch_instruction(). - */ -static int __init setup_text_poke_area(void) -{ - BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, - "powerpc/text_poke:online", text_area_cpu_up, - text_area_cpu_down)); - - return 0; -} -late_initcall(setup_text_poke_area); +struct patch_mapping { + spinlock_t *ptl; /* for protecting pte table */ + pte_t *ptep; + struct temp_mm temp_mm; +}; /* * This can be called for kernel text or a module. */ -static int map_patch_area(void *addr, unsigned long text_poke_addr) +static int map_patch(const void *addr, struct patch_mapping *patch_mapping) { - unsigned long pfn; - int err; + struct page *page; + pte_t pte; + pgprot_t pgprot; if (is_vmalloc_addr(addr)) - pfn = vmalloc_to_pfn(addr); + page = vmalloc_to_page(addr); else - pfn = __pa_symbol(addr) >> PAGE_SHIFT; + page = virt_to_page(addr); - err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL); + if (radix_enabled()) + pgprot = PAGE_KERNEL; + else + pgprot = PAGE_SHARED; - pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err); - if (err) + patch_mapping->ptep = get_locked_pte(patching_mm, patching_addr, + &patch_mapping->ptl); + if (unlikely(!patch_mapping->ptep)) { + pr_warn("map patch: failed to allocate pte for patching\n"); return -1; + } + + pte = mk_pte(page, pgprot); + if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64)) + pte = pte_mkdirty(pte); + set_pte_at(patching_mm, patching_addr, patch_mapping->ptep, pte); + + init_temp_mm(&patch_mapping->temp_mm, patching_mm); + use_temporary_mm(&patch_mapping->temp_mm); return 0; } -static inline int unmap_patch_area(unsigned long addr) +static void unmap_patch(struct patch_mapping *patch_mapping) { - pte_t *ptep; - pmd_t *pmdp; - pud_t *pudp; - pgd_t *pgdp; - - pgdp = pgd_offset_k(addr); - if (unlikely(!pgdp)) - return -EINVAL; - - pudp = pud_offset(pgdp, addr); - if (unlikely(!pudp)) - return -EINVAL; - - pmdp = pmd_offset(pudp, addr); - if (unlikely(!pmdp)) - return -EINVAL; - - ptep = pte_offset_kernel(pmdp, addr); - if (unlikely(!ptep)) - return -EINVAL; + /* In hash, pte_clear flushes the tlb */ + pte_clear(patching_mm, patching_addr, patch_mapping->ptep); + unuse_temporary_mm(&patch_mapping->temp_mm); - pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); - - /* - * In hash, pte_clear flushes the tlb, in radix, we have to - */ - pte_clear(&init_mm, addr, ptep); - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); - - return 0; + /* In radix, we have to explicitly flush the tlb (no-op in hash) */ + local_flush_tlb_mm(patching_mm); + pte_unmap_unlock(patch_mapping->ptep, patch_mapping->ptl); } static int do_patch_instruction(struct ppc_inst *addr, struct ppc_inst instr) @@ -180,32 +138,36 @@ static int do_patch_instruction(struct ppc_inst *addr, struct ppc_inst instr) int err; struct ppc_inst *patch_addr = NULL; unsigned long flags; - unsigned long text_poke_addr; - unsigned long kaddr = (unsigned long)addr; + struct patch_mapping patch_mapping; /* - * During early early boot patch_instruction is called - * when text_poke_area is not ready, but we still need - * to allow patching. We just do the plain old patching + * The patching_mm is initialized before calling mark_rodata_ro. Prior + * to this, patch_instruction is called when we don't have (and don't + * need) the patching_mm so just do plain old patching. */ - if (!this_cpu_read(text_poke_area)) + if (!patching_mm) return raw_patch_instruction(addr, instr); local_irq_save(flags); - text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; - if (map_patch_area(addr, text_poke_addr)) { - err = -1; + err = map_patch(addr, &patch_mapping); + if (err) goto out; - } - patch_addr = (struct ppc_inst *)(text_poke_addr + (kaddr & ~PAGE_MASK)); + patch_addr = (struct ppc_inst *)(patching_addr | offset_in_page(addr)); - __patch_instruction(addr, instr, patch_addr); + if (!radix_enabled()) + allow_write_to_user(patch_addr, sizeof(instr)); + err = __patch_instruction(addr, instr, patch_addr); + if (!radix_enabled()) + prevent_write_to_user(patch_addr, sizeof(instr)); - err = unmap_patch_area(text_poke_addr); - if (err) - pr_warn("failed to unmap %lx\n", text_poke_addr); + unmap_patch(&patch_mapping); + /* + * Something is wrong if what we just wrote doesn't match what we + * think we just wrote. + */ + WARN_ON(!ppc_inst_equal(ppc_inst_read(addr), instr)); out: local_irq_restore(flags);