tree: https://android.googlesource.com/kernel/common android12-5.10 head: 70c9301d9c4be76630901189cc7376eb22115a3b commit: 6971350406a366f4565bdc6b17c08ddd577f27f3 [13859/13862] ANDROID: fix mmu_notifier race caused by not taking mmap_lock during SPF config: x86_64-randconfig-r033-20211214 (https://download.01.org/0day-ci/archive/20211216/202112161632.kQZI4tAz-lk...) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): git remote add android-common https://android.googlesource.com/kernel/common git fetch --no-tags android-common android12-5.10 git checkout 6971350406a366f4565bdc6b17c08ddd577f27f3 # save the config file to linux build tree mkdir build_dir make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): mm/memory.c: In function 'handle_pte_fault': 4724 | if (!mmu_notifier_trylock(vmf->vma->vm_mm)) { | ^~~~~~~~~~~~~~~~~~~~ | mmu_notifier_unlock cc1: some warnings being treated as errors vim +4724 mm/memory.c 4616 4617 /* 4618 * These routines also need to handle stuff like marking pages dirty 4619 * and/or accessed for architectures that don't do it in hardware (most 4620 * RISC architectures). The early dirtying is also good on the i386. 4621 * 4622 * There is also a hook called "update_mmu_cache()" that architectures 4623 * with external mmu caches can use to update those (ie the Sparc or 4624 * PowerPC hashed page tables that act as extended TLBs). 4625 * 4626 * We enter with non-exclusive mmap_lock (to exclude vma changes, but allow 4627 * concurrent faults). 4628 * 4629 * The mmap_lock may have been released depending on flags and our return value. 4630 * See filemap_fault() and __lock_page_or_retry(). 4631 */ 4632 static vm_fault_t handle_pte_fault(struct vm_fault *vmf) 4633 { 4634 pte_t entry; 4635 vm_fault_t ret = 0; 4636 4637 if (unlikely(pmd_none(*vmf->pmd))) { 4638 /* 4639 * In the case of the speculative page fault handler we abort 4640 * the speculative path immediately as the pmd is probably 4641 * in the way to be converted in a huge one. We will try 4642 * again holding the mmap_sem (which implies that the collapse 4643 * operation is done). 4644 */ 4645 if (vmf->flags & FAULT_FLAG_SPECULATIVE) 4646 return VM_FAULT_RETRY; 4647 /* 4648 * Leave __pte_alloc() until later: because vm_ops->fault may 4649 * want to allocate huge page, and if we expose page table 4650 * for an instant, it will be difficult to retract from 4651 * concurrent faults and from rmap lookups. 4652 */ 4653 vmf->pte = NULL; 4654 } else if (!(vmf->flags & FAULT_FLAG_SPECULATIVE)) { 4655 /* 4656 * If a huge pmd materialized under us just retry later. Use 4657 * pmd_trans_unstable() via pmd_devmap_trans_unstable() instead 4658 * of pmd_trans_huge() to ensure the pmd didn't become 4659 * pmd_trans_huge under us and then back to pmd_none, as a 4660 * result of MADV_DONTNEED running immediately after a huge pmd 4661 * fault in a different thread of this mm, in turn leading to a 4662 * misleading pmd_trans_huge() retval. All we have to ensure is 4663 * that it is a regular pmd that we can walk with 4664 * pte_offset_map() and we can do that through an atomic read 4665 * in C, which is what pmd_trans_unstable() provides. 4666 */ 4667 if (pmd_devmap_trans_unstable(vmf->pmd)) 4668 return 0; 4669 /* 4670 * A regular pmd is established and it can't morph into a huge 4671 * pmd from under us anymore at this point because we hold the 4672 * mmap_lock read mode and khugepaged takes it in write mode. 4673 * So now it's safe to run pte_offset_map(). 4674 * This is not applicable to the speculative page fault handler 4675 * but in that case, the pte is fetched earlier in 4676 * handle_speculative_fault(). 4677 */ 4678 vmf->pte = pte_offset_map(vmf->pmd, vmf->address); 4679 vmf->orig_pte = *vmf->pte; 4680 4681 /* 4682 * some architectures can have larger ptes than wordsize, 4683 * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and 4684 * CONFIG_32BIT=y, so READ_ONCE cannot guarantee atomic 4685 * accesses. The code below just needs a consistent view 4686 * for the ifs and we later double check anyway with the 4687 * ptl lock held. So here a barrier will do. 4688 */ 4689 barrier(); 4690 if (pte_none(vmf->orig_pte)) { 4691 pte_unmap(vmf->pte); 4692 vmf->pte = NULL; 4693 } 4694 } 4695 4696 if (!vmf->pte) { 4697 if (vma_is_anonymous(vmf->vma)) 4698 return do_anonymous_page(vmf); 4699 else if ((vmf->flags & FAULT_FLAG_SPECULATIVE) && 4700 !vmf_allows_speculation(vmf)) 4701 return VM_FAULT_RETRY; 4702 else 4703 return do_fault(vmf); 4704 } 4705 4706 if (!pte_present(vmf->orig_pte)) 4707 return do_swap_page(vmf); 4708 4709 if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma)) 4710 return do_numa_page(vmf); 4711 4712 if (!pte_spinlock(vmf)) 4713 return VM_FAULT_RETRY; 4714 entry = vmf->orig_pte; 4715 if (unlikely(!pte_same(*vmf->pte, entry))) { 4716 update_mmu_tlb(vmf->vma, vmf->address, vmf->pte); 4717 goto unlock; 4718 } 4719 if (vmf->flags & FAULT_FLAG_WRITE) { 4720 if (!pte_write(entry)) { 4721 if (!(vmf->flags & FAULT_FLAG_SPECULATIVE)) 4722 return do_wp_page(vmf); 4723 4725 ret = VM_FAULT_RETRY; 4726 goto unlock; 4727 } 4728 4729 ret = do_wp_page(vmf); 4730 mmu_notifier_unlock(vmf->vma->vm_mm); 4731 return ret; 4732 } 4733 entry = pte_mkdirty(entry); 4734 } 4735 entry = pte_mkyoung(entry); 4736 if (ptep_set_access_flags(vmf->vma, vmf->address, vmf->pte, entry, 4737 vmf->flags & FAULT_FLAG_WRITE)) { 4738 update_mmu_cache(vmf->vma, vmf->address, vmf->pte); 4739 } else { 4740 /* Skip spurious TLB flush for retried page fault */ 4741 if (vmf->flags & FAULT_FLAG_TRIED) 4742 goto unlock; 4743 if (vmf->flags & FAULT_FLAG_SPECULATIVE) 4744 ret = VM_FAULT_RETRY; 4745 /* 4746 * This is needed only for protection faults but the arch code 4747 * is not yet telling us if this is a protection fault or not. 4748 * This still avoids useless tlb flushes for .text page faults 4749 * with threads. 4750 */ 4751 if (vmf->flags & FAULT_FLAG_WRITE) 4752 flush_tlb_fix_spurious_fault(vmf->vma, vmf->address); 4753 } 4754 unlock: 4755 pte_unmap_unlock(vmf->pte, vmf->ptl); 4756 return ret; 4757 } 4758 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org