From patchwork Wed Oct 9 08:42:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jia He X-Patchwork-Id: 11180809 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 3D8DD1709 for ; Wed, 9 Oct 2019 08:43:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 02CC0218AC for ; Wed, 9 Oct 2019 08:43:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02CC0218AC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 373928E0009; Wed, 9 Oct 2019 04:43:34 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 325278E0003; Wed, 9 Oct 2019 04:43:34 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 261698E0009; Wed, 9 Oct 2019 04:43:34 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0167.hostedemail.com [216.40.44.167]) by kanga.kvack.org (Postfix) with ESMTP id 06F838E0003 for ; Wed, 9 Oct 2019 04:43:33 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id C183D40E8 for ; Wed, 9 Oct 2019 08:43:32 +0000 (UTC) X-FDA: 76023607464.25.spade93_58d1659553c15 X-Spam-Summary: 2,0,0,d08ca6257578d572,d41d8cd98f00b204,justin.he@arm.com,:catalin.marinas@arm.com:will@kernel.org:mark.rutland@arm.com:james.morse@arm.com:maz@kernel.org:willy@infradead.org:kirill.shutemov@linux.intel.com:linux-arm-kernel@lists.infradead.org:linux-kernel@vger.kernel.org::suzuki.poulose@arm.com:bp@alien8.de:hpa@zytor.com:x86@kernel.org:tglx@linutronix.de:akpm@linux-foundation.org:hejianet@gmail.com:kaly.xin@arm.com:nd@arm.com:justin.he@arm.com,RULES_HIT:2:41:355:379:541:800:960:967:973:988:989:1042:1260:1261:1345:1359:1437:1535:1605:1730:1747:1777:1792:2194:2199:2393:2525:2559:2563:2682:2685:2693:2859:2901:2918:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3865:3866:3867:3868:3870:3871:3872:3873:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4049:4118:4250:4321:4605:5007:6117:6119:6261:6671:6737:7208:7903:8634:8660:9025:9108:10004:11026:11473:11658:11914:12043:12048:12291:12295:12296:12297:12438:12555:12683:12895:12986:13007:13 148:1316 X-HE-Tag: spade93_58d1659553c15 X-Filterd-Recvd-Size: 7685 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Oct 2019 08:43:30 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8F06B1000; Wed, 9 Oct 2019 01:43:29 -0700 (PDT) Received: from localhost.localdomain (entos-thunderx2-02.shanghai.arm.com [10.169.40.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id EAD153F68E; Wed, 9 Oct 2019 01:43:24 -0700 (PDT) From: Jia He To: Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Suzuki Poulose , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org Cc: Thomas Gleixner , Andrew Morton , hejianet@gmail.com, Kaly Xin , nd@arm.com, Jia He Subject: [PATCH v11 4/4] mm: fix double page fault on arm64 if PTE_AF is cleared Date: Wed, 9 Oct 2019 16:42:46 +0800 Message-Id: <20191009084246.123354-5-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191009084246.123354-1-justin.he@arm.com> References: <20191009084246.123354-1-justin.he@arm.com> 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 we tested pmdk unit test [1] vmmalloc_fork TEST3 on arm64 guest, there will be a double page fault in __copy_from_user_inatomic of cow_user_page. To reproduce the bug, the cmd is as follows after you deployed everything: make -C src/test/vmmalloc_fork/ TEST_TIME=60m check Below call trace is from arm64 do_page_fault for debugging purpose: [ 110.016195] Call trace: [ 110.016826] do_page_fault+0x5a4/0x690 [ 110.017812] do_mem_abort+0x50/0xb0 [ 110.018726] el1_da+0x20/0xc4 [ 110.019492] __arch_copy_from_user+0x180/0x280 [ 110.020646] do_wp_page+0xb0/0x860 [ 110.021517] __handle_mm_fault+0x994/0x1338 [ 110.022606] handle_mm_fault+0xe8/0x180 [ 110.023584] do_page_fault+0x240/0x690 [ 110.024535] do_mem_abort+0x50/0xb0 [ 110.025423] el0_da+0x20/0x24 The pte info before __copy_from_user_inatomic is (PTE_AF is cleared): [ffff9b007000] pgd=000000023d4f8003, pud=000000023da9b003, pmd=000000023d4b3003, pte=360000298607bd3 As told by Catalin: "On arm64 without hardware Access Flag, copying from user will fail because the pte is old and cannot be marked young. So we always end up with zeroed page after fork() + CoW for pfn mappings. we don't always have a hardware-managed access flag on arm64." This patch fixes it by calling pte_mkyoung. Also, the parameter is changed because vmf should be passed to cow_user_page() Add a WARN_ON_ONCE when __copy_from_user_inatomic() returns error in case there can be some obscure use-case (by Kirill). [1] https://github.com/pmem/pmdk/tree/master/src/test/vmmalloc_fork Signed-off-by: Jia He Reported-by: Yibo Cai Reviewed-by: Catalin Marinas Acked-by: Kirill A. Shutemov --- mm/memory.c | 104 ++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 89 insertions(+), 15 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index b1ca51a079f2..b6a5d6a08438 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -118,6 +118,18 @@ int randomize_va_space __read_mostly = 2; #endif +#ifndef arch_faults_on_old_pte +static inline bool arch_faults_on_old_pte(void) +{ + /* + * Those arches which don't have hw access flag feature need to + * implement their own helper. By default, "true" means pagefault + * will be hit on old pte. + */ + return true; +} +#endif + static int __init disable_randmaps(char *s) { randomize_va_space = 0; @@ -2145,32 +2157,82 @@ static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, return same; } -static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma) +static inline bool cow_user_page(struct page *dst, struct page *src, + struct vm_fault *vmf) { + bool ret; + void *kaddr; + void __user *uaddr; + bool force_mkyoung; + struct vm_area_struct *vma = vmf->vma; + struct mm_struct *mm = vma->vm_mm; + unsigned long addr = vmf->address; + debug_dma_assert_idle(src); + if (likely(src)) { + copy_user_highpage(dst, src, addr, vma); + return true; + } + /* * If the source page was a PFN mapping, we don't have * a "struct page" for it. We do a best-effort copy by * just copying from the original user address. If that * fails, we just zero-fill it. Live with it. */ - if (unlikely(!src)) { - void *kaddr = kmap_atomic(dst); - void __user *uaddr = (void __user *)(va & PAGE_MASK); + kaddr = kmap_atomic(dst); + uaddr = (void __user *)(addr & PAGE_MASK); + + /* + * On architectures with software "accessed" bits, we would + * take a double page fault, so mark it accessed here. + */ + force_mkyoung = arch_faults_on_old_pte() && !pte_young(vmf->orig_pte); + if (force_mkyoung) { + pte_t entry; + + vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl); + if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) { + /* + * Other thread has already handled the fault + * and we don't need to do anything. If it's + * not the case, the fault will be triggered + * again on the same address. + */ + ret = false; + goto pte_unlock; + } + entry = pte_mkyoung(vmf->orig_pte); + if (ptep_set_access_flags(vma, addr, vmf->pte, entry, 0)) + update_mmu_cache(vma, addr, vmf->pte); + } + + /* + * This really shouldn't fail, because the page is there + * in the page tables. But it might just be unreadable, + * in which case we just give up and fill the result with + * zeroes. + */ + if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { /* - * This really shouldn't fail, because the page is there - * in the page tables. But it might just be unreadable, - * in which case we just give up and fill the result with - * zeroes. + * Give a warn in case there can be some obscure + * use-case */ - if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) - clear_page(kaddr); - kunmap_atomic(kaddr); - flush_dcache_page(dst); - } else - copy_user_highpage(dst, src, va, vma); + WARN_ON_ONCE(1); + clear_page(kaddr); + } + + ret = true; + +pte_unlock: + if (force_mkyoung) + pte_unmap_unlock(vmf->pte, vmf->ptl); + kunmap_atomic(kaddr); + flush_dcache_page(dst); + + return ret; } static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma) @@ -2327,7 +2389,19 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) vmf->address); if (!new_page) goto oom; - cow_user_page(new_page, old_page, vmf->address, vma); + + if (!cow_user_page(new_page, old_page, vmf)) { + /* + * COW failed, if the fault was solved by other, + * it's fine. If not, userspace would re-fault on + * the same address and we will handle the fault + * from the second attempt. + */ + put_page(new_page); + if (old_page) + put_page(old_page); + return 0; + } } if (mem_cgroup_try_charge_delay(new_page, mm, GFP_KERNEL, &memcg, false))