| Message ID | 20190416134522.17540-11-ldufour@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Speculative page faults | expand |
On Tue, Apr 16, 2019 at 03:45:01PM +0200, Laurent Dufour wrote: > 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 <ldufour@linux.ibm.com> Reviewed-by: Jérôme Glisse <jglisse@redhat.com> > --- > 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 | 28 ++++++++++++++++--------- > mm/mprotect.c | 4 +++- > mm/swap_state.c | 10 ++++++--- > 9 files changed, 95 insertions(+), 42 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 01d4eb0e6bd1..0864c050b2de 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1162,8 +1162,11 @@ 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 3b30301c90ec..2e0f98cadd81 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -667,8 +667,11 @@ 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; > } > > @@ -908,8 +911,10 @@ 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); > } > skip_mm: > up_write(&mm->mmap_sem); > @@ -1474,8 +1479,10 @@ 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; > @@ -1636,8 +1643,10 @@ 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 a335f7c1fac4..6a0cbca3885e 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1011,6 +1011,7 @@ 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); > @@ -1046,6 +1047,7 @@ 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; > } > @@ -1081,6 +1083,7 @@ 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 a692d2a893b5..6cf07dc546fc 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 2219e747df49..94c103c5034a 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); > } > > @@ -575,9 +578,11 @@ 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; > } > @@ -683,6 +688,7 @@ 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) > @@ -690,11 +696,17 @@ 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 accesses 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; > } > @@ -1654,23 +1666,28 @@ COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid, > 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 080f3b36415b..f390903d9bbb 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; > @@ -569,10 +571,11 @@ 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 a4e4d52a5148..b77ec0149249 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -877,17 +877,18 @@ 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) { > @@ -1850,12 +1851,14 @@ 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) || vma_is_dax(vma) || > is_vm_hugetlb_page(vma) || > vma == get_gate_vma(current->mm)) > - vma->vm_flags &= VM_LOCKED_CLEAR_MASK; > + WRITE_ONCE(vma->vm_flags, > + vma->vm_flags &= VM_LOCKED_CLEAR_MASK); > else > mm->locked_vm += (len >> PAGE_SHIFT); > } > @@ -1870,9 +1873,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > * then new mapped in-place (which must be aimed as > * a completely new data area). > */ > - vma->vm_flags |= VM_SOFTDIRTY; > + WRITE_ONCE(vma->vm_flags, vma->vm_flags | VM_SOFTDIRTY); > > vma_set_page_prot(vma); > + vm_write_end(vma); > > return addr; > > @@ -2430,7 +2434,9 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) > mm->locked_vm += grow; > vm_stat_account(mm, vma->vm_flags, grow); > anon_vma_interval_tree_pre_update_vma(vma); > - vma->vm_end = address; > + vm_write_begin(vma); > + WRITE_ONCE(vma->vm_end, address); > + vm_write_end(vma); > anon_vma_interval_tree_post_update_vma(vma); > if (vma->vm_next) > vma_gap_update(vma->vm_next); > @@ -2510,8 +2516,10 @@ 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; > + vm_write_begin(vma); > + WRITE_ONCE(vma->vm_start, address); > + WRITE_ONCE(vma->vm_pgoff, vma->vm_pgoff - grow); > + vm_write_end(vma); > 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 65242f1e4457..78fce873ca3a 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -427,12 +427,14 @@ 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); > > change_protection(vma, start, end, vma->vm_page_prot, > dirty_accountable, 0); > + vm_write_end(vma); > > /* > * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major > diff --git a/mm/swap_state.c b/mm/swap_state.c > index eb714165afd2..c45f9122b457 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -523,7 +523,11 @@ static unsigned long swapin_nr_pages(unsigned long offset) > * This has been extended to use the NUMA policies from the mm triggering > * the readahead. > * > - * Caller must hold read mmap_sem if vmf->vma is not NULL. > + * 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) > @@ -624,9 +628,9 @@ 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)); > } > > -- > 2.21.0 >
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 01d4eb0e6bd1..0864c050b2de 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1162,8 +1162,11 @@ 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 3b30301c90ec..2e0f98cadd81 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -667,8 +667,11 @@ 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; } @@ -908,8 +911,10 @@ 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); } skip_mm: up_write(&mm->mmap_sem); @@ -1474,8 +1479,10 @@ 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; @@ -1636,8 +1643,10 @@ 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 a335f7c1fac4..6a0cbca3885e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1011,6 +1011,7 @@ 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); @@ -1046,6 +1047,7 @@ 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; } @@ -1081,6 +1083,7 @@ 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 a692d2a893b5..6cf07dc546fc 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 2219e747df49..94c103c5034a 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); } @@ -575,9 +578,11 @@ 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; } @@ -683,6 +688,7 @@ 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) @@ -690,11 +696,17 @@ 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 accesses 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; } @@ -1654,23 +1666,28 @@ COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid, 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 080f3b36415b..f390903d9bbb 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; @@ -569,10 +571,11 @@ 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 a4e4d52a5148..b77ec0149249 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -877,17 +877,18 @@ 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) { @@ -1850,12 +1851,14 @@ 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) || vma_is_dax(vma) || is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm)) - vma->vm_flags &= VM_LOCKED_CLEAR_MASK; + WRITE_ONCE(vma->vm_flags, + vma->vm_flags &= VM_LOCKED_CLEAR_MASK); else mm->locked_vm += (len >> PAGE_SHIFT); } @@ -1870,9 +1873,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr, * then new mapped in-place (which must be aimed as * a completely new data area). */ - vma->vm_flags |= VM_SOFTDIRTY; + WRITE_ONCE(vma->vm_flags, vma->vm_flags | VM_SOFTDIRTY); vma_set_page_prot(vma); + vm_write_end(vma); return addr; @@ -2430,7 +2434,9 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) mm->locked_vm += grow; vm_stat_account(mm, vma->vm_flags, grow); anon_vma_interval_tree_pre_update_vma(vma); - vma->vm_end = address; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_end, address); + vm_write_end(vma); anon_vma_interval_tree_post_update_vma(vma); if (vma->vm_next) vma_gap_update(vma->vm_next); @@ -2510,8 +2516,10 @@ 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; + vm_write_begin(vma); + WRITE_ONCE(vma->vm_start, address); + WRITE_ONCE(vma->vm_pgoff, vma->vm_pgoff - grow); + vm_write_end(vma); 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 65242f1e4457..78fce873ca3a 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -427,12 +427,14 @@ 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); change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable, 0); + vm_write_end(vma); /* * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major diff --git a/mm/swap_state.c b/mm/swap_state.c index eb714165afd2..c45f9122b457 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -523,7 +523,11 @@ static unsigned long swapin_nr_pages(unsigned long offset) * This has been extended to use the NUMA policies from the mm triggering * the readahead. * - * Caller must hold read mmap_sem if vmf->vma is not NULL. + * 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) @@ -624,9 +628,9 @@ 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)); }
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 <ldufour@linux.ibm.com> --- 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 | 28 ++++++++++++++++--------- mm/mprotect.c | 4 +++- mm/swap_state.c | 10 ++++++--- 9 files changed, 95 insertions(+), 42 deletions(-)