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Violators will be prosecuted; Tue, 13 Mar 2018 18:00:14 -0000 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w2DI0DrY25690262; Tue, 13 Mar 2018 18:00:13 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D1AAA4204B; Tue, 13 Mar 2018 17:52:29 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B5F8842041; Tue, 13 Mar 2018 17:52:28 +0000 (GMT) Received: from nimbus.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.33]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 13 Mar 2018 17:52:28 +0000 (GMT) From: Laurent Dufour To: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com, Daniel Jordan Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: [PATCH v9 08/24] mm: Protect VMA modifications using VMA sequence count Date: Tue, 13 Mar 2018 18:59:38 +0100 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1520963994-28477-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1520963994-28477-1-git-send-email-ldufour@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18031318-0016-0000-0000-000005320194 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18031318-0017-0000-0000-0000286F0185 Message-Id: <1520963994-28477-9-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-13_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803130203 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The VMA sequence count has been introduced to allow fast detection of VMA modification when running a page fault handler without holding the mmap_sem. This patch provides protection against the VMA modification done in : - madvise() - mpol_rebind_policy() - vma_replace_policy() - change_prot_numa() - mlock(), munlock() - mprotect() - mmap_region() - collapse_huge_page() - userfaultd registering services In addition, VMA fields which will be read during the speculative fault path needs to be written using WRITE_ONCE to prevent write to be split and intermediate values to be pushed to other CPUs. Signed-off-by: Laurent Dufour --- fs/proc/task_mmu.c | 5 ++++- fs/userfaultfd.c | 17 +++++++++++++---- mm/khugepaged.c | 3 +++ mm/madvise.c | 6 +++++- mm/mempolicy.c | 51 ++++++++++++++++++++++++++++++++++----------------- mm/mlock.c | 13 ++++++++----- mm/mmap.c | 17 ++++++++++------- mm/mprotect.c | 4 +++- mm/swap_state.c | 8 ++++++-- 9 files changed, 86 insertions(+), 38 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 65ae54659833..a2d9c87b7b0b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1136,8 +1136,11 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, goto out_mm; } for (vma = mm->mmap; vma; vma = vma->vm_next) { - vma->vm_flags &= ~VM_SOFTDIRTY; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, + vma->vm_flags & ~VM_SOFTDIRTY); vma_set_page_prot(vma); + vm_write_end(vma); } downgrade_write(&mm->mmap_sem); break; diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index cec550c8468f..b8212ba17695 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -659,8 +659,11 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) octx = vma->vm_userfaultfd_ctx.ctx; if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { + vm_write_begin(vma); vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; - vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); + WRITE_ONCE(vma->vm_flags, + vma->vm_flags & ~(VM_UFFD_WP | VM_UFFD_MISSING)); + vm_write_end(vma); return 0; } @@ -885,8 +888,10 @@ static int userfaultfd_release(struct inode *inode, struct file *file) vma = prev; else prev = vma; - vma->vm_flags = new_flags; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, new_flags); vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; + vm_write_end(vma); } up_write(&mm->mmap_sem); mmput(mm); @@ -1434,8 +1439,10 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, * the next vma was merged into the current one and * the current one has not been updated yet. */ - vma->vm_flags = new_flags; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, new_flags); vma->vm_userfaultfd_ctx.ctx = ctx; + vm_write_end(vma); skip: prev = vma; @@ -1592,8 +1599,10 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, * the next vma was merged into the current one and * the current one has not been updated yet. */ - vma->vm_flags = new_flags; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, new_flags); vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; + vm_write_end(vma); skip: prev = vma; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index b7e2268dfc9a..32314e9e48dd 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1006,6 +1006,7 @@ static void collapse_huge_page(struct mm_struct *mm, if (mm_find_pmd(mm, address) != pmd) goto out; + vm_write_begin(vma); anon_vma_lock_write(vma->anon_vma); pte = pte_offset_map(pmd, address); @@ -1041,6 +1042,7 @@ static void collapse_huge_page(struct mm_struct *mm, pmd_populate(mm, pmd, pmd_pgtable(_pmd)); spin_unlock(pmd_ptl); anon_vma_unlock_write(vma->anon_vma); + vm_write_end(vma); result = SCAN_FAIL; goto out; } @@ -1075,6 +1077,7 @@ static void collapse_huge_page(struct mm_struct *mm, set_pmd_at(mm, address, pmd, _pmd); update_mmu_cache_pmd(vma, address, pmd); spin_unlock(pmd_ptl); + vm_write_end(vma); *hpage = NULL; diff --git a/mm/madvise.c b/mm/madvise.c index 4d3c922ea1a1..e328f7ab5942 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -184,7 +184,9 @@ static long madvise_behavior(struct vm_area_struct *vma, /* * vm_flags is protected by the mmap_sem held in write mode. */ - vma->vm_flags = new_flags; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, new_flags); + vm_write_end(vma); out: return error; } @@ -450,9 +452,11 @@ static void madvise_free_page_range(struct mmu_gather *tlb, .private = tlb, }; + vm_write_begin(vma); tlb_start_vma(tlb, vma); walk_page_range(addr, end, &free_walk); tlb_end_vma(tlb, vma); + vm_write_end(vma); } static int madvise_free_single_vma(struct vm_area_struct *vma, diff --git a/mm/mempolicy.c b/mm/mempolicy.c index e0e706f0b34e..2632c6f93b63 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -380,8 +380,11 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) struct vm_area_struct *vma; down_write(&mm->mmap_sem); - for (vma = mm->mmap; vma; vma = vma->vm_next) + for (vma = mm->mmap; vma; vma = vma->vm_next) { + vm_write_begin(vma); mpol_rebind_policy(vma->vm_policy, new); + vm_write_end(vma); + } up_write(&mm->mmap_sem); } @@ -554,9 +557,11 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, { int nr_updated; + vm_write_begin(vma); nr_updated = change_protection(vma, addr, end, PAGE_NONE, 0, 1); if (nr_updated) count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated); + vm_write_end(vma); return nr_updated; } @@ -657,6 +662,7 @@ static int vma_replace_policy(struct vm_area_struct *vma, if (IS_ERR(new)) return PTR_ERR(new); + vm_write_begin(vma); if (vma->vm_ops && vma->vm_ops->set_policy) { err = vma->vm_ops->set_policy(vma, new); if (err) @@ -664,11 +670,17 @@ static int vma_replace_policy(struct vm_area_struct *vma, } old = vma->vm_policy; - vma->vm_policy = new; /* protected by mmap_sem */ + /* + * The speculative page fault handler access this field without + * hodling the mmap_sem. + */ + WRITE_ONCE(vma->vm_policy, new); + vm_write_end(vma); mpol_put(old); return 0; err_out: + vm_write_end(vma); mpol_put(new); return err; } @@ -1552,23 +1564,28 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len, struct mempolicy *__get_vma_policy(struct vm_area_struct *vma, unsigned long addr) { - struct mempolicy *pol = NULL; + struct mempolicy *pol; - if (vma) { - if (vma->vm_ops && vma->vm_ops->get_policy) { - pol = vma->vm_ops->get_policy(vma, addr); - } else if (vma->vm_policy) { - pol = vma->vm_policy; + if (!vma) + return NULL; - /* - * shmem_alloc_page() passes MPOL_F_SHARED policy with - * a pseudo vma whose vma->vm_ops=NULL. Take a reference - * count on these policies which will be dropped by - * mpol_cond_put() later - */ - if (mpol_needs_cond_ref(pol)) - mpol_get(pol); - } + if (vma->vm_ops && vma->vm_ops->get_policy) + return vma->vm_ops->get_policy(vma, addr); + + /* + * This could be called without holding the mmap_sem in the + * speculative page fault handler's path. + */ + pol = READ_ONCE(vma->vm_policy); + if (pol) { + /* + * shmem_alloc_page() passes MPOL_F_SHARED policy with + * a pseudo vma whose vma->vm_ops=NULL. Take a reference + * count on these policies which will be dropped by + * mpol_cond_put() later + */ + if (mpol_needs_cond_ref(pol)) + mpol_get(pol); } return pol; diff --git a/mm/mlock.c b/mm/mlock.c index 74e5a6547c3d..c40285c94ced 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -445,7 +445,9 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, void munlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end) { - vma->vm_flags &= VM_LOCKED_CLEAR_MASK; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, vma->vm_flags & VM_LOCKED_CLEAR_MASK); + vm_write_end(vma); while (start < end) { struct page *page; @@ -568,10 +570,11 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev, * It's okay if try_to_unmap_one unmaps a page just after we * set VM_LOCKED, populate_vma_page_range will bring it back. */ - - if (lock) - vma->vm_flags = newflags; - else + if (lock) { + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, newflags); + vm_write_end(vma); + } else munlock_vma_pages_range(vma, start, end); out: diff --git a/mm/mmap.c b/mm/mmap.c index 5898255d0aeb..d6533cb85213 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -847,17 +847,18 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, } if (start != vma->vm_start) { - vma->vm_start = start; + WRITE_ONCE(vma->vm_start, start); start_changed = true; } if (end != vma->vm_end) { - vma->vm_end = end; + WRITE_ONCE(vma->vm_end, end); end_changed = true; } - vma->vm_pgoff = pgoff; + WRITE_ONCE(vma->vm_pgoff, pgoff); if (adjust_next) { - next->vm_start += adjust_next << PAGE_SHIFT; - next->vm_pgoff += adjust_next; + WRITE_ONCE(next->vm_start, + next->vm_start + (adjust_next << PAGE_SHIFT)); + WRITE_ONCE(next->vm_pgoff, next->vm_pgoff + adjust_next); } if (root) { @@ -1781,6 +1782,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, out: perf_event_mmap(vma); + vm_write_begin(vma); vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT); if (vm_flags & VM_LOCKED) { if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) || @@ -1803,6 +1805,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma->vm_flags |= VM_SOFTDIRTY; vma_set_page_prot(vma); + vm_write_end(vma); return addr; @@ -2431,8 +2434,8 @@ int expand_downwards(struct vm_area_struct *vma, mm->locked_vm += grow; vm_stat_account(mm, vma->vm_flags, grow); anon_vma_interval_tree_pre_update_vma(vma); - vma->vm_start = address; - vma->vm_pgoff -= grow; + WRITE_ONCE(vma->vm_start, address); + WRITE_ONCE(vma->vm_pgoff, vma->vm_pgoff - grow); anon_vma_interval_tree_post_update_vma(vma); vma_gap_update(vma); spin_unlock(&mm->page_table_lock); diff --git a/mm/mprotect.c b/mm/mprotect.c index e3309fcf586b..9b7a71c30287 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -366,7 +366,8 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, * vm_flags and vm_page_prot are protected by the mmap_sem * held in write mode. */ - vma->vm_flags = newflags; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_flags, newflags); dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot); vma_set_page_prot(vma); @@ -381,6 +382,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, (newflags & VM_WRITE)) { populate_vma_page_range(vma, start, end, NULL); } + vm_write_end(vma); vm_stat_account(mm, oldflags, -nrpages); vm_stat_account(mm, newflags, nrpages); diff --git a/mm/swap_state.c b/mm/swap_state.c index 486f7c26386e..691bd6e06967 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -575,6 +575,10 @@ static unsigned long swapin_nr_pages(unsigned long offset) * the readahead. * * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL. + * This is needed to ensure the VMA will not be freed in our back. In the case + * of the speculative page fault handler, this cannot happen, even if we don't + * hold the mmap_sem. Callees are assumed to take care of reading VMA's fields + * using READ_ONCE() to read consistent values. */ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, struct vm_fault *vmf) @@ -669,9 +673,9 @@ static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma, unsigned long *start, unsigned long *end) { - *start = max3(lpfn, PFN_DOWN(vma->vm_start), + *start = max3(lpfn, PFN_DOWN(READ_ONCE(vma->vm_start)), PFN_DOWN(faddr & PMD_MASK)); - *end = min3(rpfn, PFN_DOWN(vma->vm_end), + *end = min3(rpfn, PFN_DOWN(READ_ONCE(vma->vm_end)), PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE)); } -- 2.7.4