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![Mike Kravetz](/assets/img/avatar_default.png)
hugetlb uses a fault mutex hash table to prevent page faults of the same pages concurrently. The key for shared and private mappings is different. Shared keys off address_space and file index. Private keys off mm and virtual address. Consider a private mappings of a populated hugetlbfs file. A fault will map the page from the file and if needed do a COW to map a writable page. Hugetlbfs hole punch uses the fault mutex to prevent mappings of file pages. It uses the address_space file index key. However, private mappings will use a different key and could race with this code to map the file page. This causes problems (BUG) for the page cache remove code as it expects the page to be unmapped. A sample stack is: page dumped because: VM_BUG_ON_PAGE(page_mapped(page)) kernel BUG at mm/filemap.c:169! ... RIP: 0010:unaccount_page_cache_page+0x1b8/0x200 ... Call Trace: __delete_from_page_cache+0x39/0x220 delete_from_page_cache+0x45/0x70 remove_inode_hugepages+0x13c/0x380 ? __add_to_page_cache_locked+0x162/0x380 hugetlbfs_fallocate+0x403/0x540 ? _cond_resched+0x15/0x30 ? __inode_security_revalidate+0x5d/0x70 ? selinux_file_permission+0x100/0x130 vfs_fallocate+0x13f/0x270 ksys_fallocate+0x3c/0x80 __x64_sys_fallocate+0x1a/0x20 do_syscall_64+0x5b/0x180 entry_SYSCALL_64_after_hwframe+0x44/0xa9 There seems to be another potential COW issue/race with this approach of different private and shared keys as noted in commit8382d914eb
("mm, hugetlb: improve page-fault scalability"). Since every hugetlb mapping (even anon and private) is actually a file mapping, just use the address_space index key for all mappings. This results in potentially more hash collisions. However, this should not be the common case. Link: http://lkml.kernel.org/r/20190328234704.27083-3-mike.kravetz@oracle.com Link: http://lkml.kernel.org/r/20190412165235.t4sscoujczfhuiyt@linux-r8p5 Fixes:b5cec28d36
("hugetlbfs: truncate_hugepages() takes a range of pages") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
616 lines
16 KiB
C
616 lines
16 KiB
C
/*
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* mm/userfaultfd.c
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*
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* Copyright (C) 2015 Red Hat, Inc.
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*/
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#include <linux/mm.h>
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#include <linux/sched/signal.h>
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#include <linux/pagemap.h>
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#include <linux/rmap.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/userfaultfd_k.h>
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#include <linux/mmu_notifier.h>
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#include <linux/hugetlb.h>
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#include <linux/shmem_fs.h>
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#include <asm/tlbflush.h>
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#include "internal.h"
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static int mcopy_atomic_pte(struct mm_struct *dst_mm,
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pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr,
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unsigned long src_addr,
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struct page **pagep)
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{
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struct mem_cgroup *memcg;
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pte_t _dst_pte, *dst_pte;
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spinlock_t *ptl;
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void *page_kaddr;
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int ret;
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struct page *page;
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pgoff_t offset, max_off;
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struct inode *inode;
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if (!*pagep) {
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ret = -ENOMEM;
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page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
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if (!page)
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goto out;
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page_kaddr = kmap_atomic(page);
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ret = copy_from_user(page_kaddr,
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(const void __user *) src_addr,
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PAGE_SIZE);
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kunmap_atomic(page_kaddr);
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/* fallback to copy_from_user outside mmap_sem */
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if (unlikely(ret)) {
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ret = -ENOENT;
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*pagep = page;
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/* don't free the page */
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goto out;
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}
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} else {
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page = *pagep;
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*pagep = NULL;
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}
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/*
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* The memory barrier inside __SetPageUptodate makes sure that
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* preceeding stores to the page contents become visible before
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* the set_pte_at() write.
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*/
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__SetPageUptodate(page);
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ret = -ENOMEM;
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if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false))
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goto out_release;
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_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
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if (dst_vma->vm_flags & VM_WRITE)
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_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
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dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
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if (dst_vma->vm_file) {
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/* the shmem MAP_PRIVATE case requires checking the i_size */
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inode = dst_vma->vm_file->f_inode;
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offset = linear_page_index(dst_vma, dst_addr);
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max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
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ret = -EFAULT;
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if (unlikely(offset >= max_off))
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goto out_release_uncharge_unlock;
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}
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ret = -EEXIST;
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if (!pte_none(*dst_pte))
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goto out_release_uncharge_unlock;
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inc_mm_counter(dst_mm, MM_ANONPAGES);
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page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
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mem_cgroup_commit_charge(page, memcg, false, false);
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lru_cache_add_active_or_unevictable(page, dst_vma);
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set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
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/* No need to invalidate - it was non-present before */
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update_mmu_cache(dst_vma, dst_addr, dst_pte);
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pte_unmap_unlock(dst_pte, ptl);
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ret = 0;
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out:
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return ret;
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out_release_uncharge_unlock:
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pte_unmap_unlock(dst_pte, ptl);
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mem_cgroup_cancel_charge(page, memcg, false);
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out_release:
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put_page(page);
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goto out;
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}
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static int mfill_zeropage_pte(struct mm_struct *dst_mm,
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pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr)
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{
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pte_t _dst_pte, *dst_pte;
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spinlock_t *ptl;
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int ret;
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pgoff_t offset, max_off;
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struct inode *inode;
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_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
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dst_vma->vm_page_prot));
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dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
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if (dst_vma->vm_file) {
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/* the shmem MAP_PRIVATE case requires checking the i_size */
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inode = dst_vma->vm_file->f_inode;
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offset = linear_page_index(dst_vma, dst_addr);
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max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
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ret = -EFAULT;
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if (unlikely(offset >= max_off))
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goto out_unlock;
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}
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ret = -EEXIST;
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if (!pte_none(*dst_pte))
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goto out_unlock;
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set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
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/* No need to invalidate - it was non-present before */
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update_mmu_cache(dst_vma, dst_addr, dst_pte);
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ret = 0;
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out_unlock:
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pte_unmap_unlock(dst_pte, ptl);
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return ret;
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}
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static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
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{
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pgd_t *pgd;
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p4d_t *p4d;
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pud_t *pud;
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pgd = pgd_offset(mm, address);
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p4d = p4d_alloc(mm, pgd, address);
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if (!p4d)
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return NULL;
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pud = pud_alloc(mm, p4d, address);
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if (!pud)
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return NULL;
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/*
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* Note that we didn't run this because the pmd was
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* missing, the *pmd may be already established and in
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* turn it may also be a trans_huge_pmd.
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*/
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return pmd_alloc(mm, pud, address);
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}
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#ifdef CONFIG_HUGETLB_PAGE
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/*
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* __mcopy_atomic processing for HUGETLB vmas. Note that this routine is
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* called with mmap_sem held, it will release mmap_sem before returning.
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*/
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static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
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struct vm_area_struct *dst_vma,
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unsigned long dst_start,
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unsigned long src_start,
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unsigned long len,
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bool zeropage)
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{
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int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED;
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int vm_shared = dst_vma->vm_flags & VM_SHARED;
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ssize_t err;
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pte_t *dst_pte;
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unsigned long src_addr, dst_addr;
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long copied;
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struct page *page;
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struct hstate *h;
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unsigned long vma_hpagesize;
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pgoff_t idx;
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u32 hash;
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struct address_space *mapping;
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/*
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* There is no default zero huge page for all huge page sizes as
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* supported by hugetlb. A PMD_SIZE huge pages may exist as used
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* by THP. Since we can not reliably insert a zero page, this
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* feature is not supported.
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*/
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if (zeropage) {
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up_read(&dst_mm->mmap_sem);
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return -EINVAL;
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}
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src_addr = src_start;
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dst_addr = dst_start;
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copied = 0;
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page = NULL;
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vma_hpagesize = vma_kernel_pagesize(dst_vma);
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/*
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* Validate alignment based on huge page size
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*/
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err = -EINVAL;
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if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
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goto out_unlock;
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retry:
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/*
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* On routine entry dst_vma is set. If we had to drop mmap_sem and
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* retry, dst_vma will be set to NULL and we must lookup again.
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*/
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if (!dst_vma) {
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err = -ENOENT;
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dst_vma = find_vma(dst_mm, dst_start);
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if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
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goto out_unlock;
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/*
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* Check the vma is registered in uffd, this is
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* required to enforce the VM_MAYWRITE check done at
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* uffd registration time.
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*/
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if (!dst_vma->vm_userfaultfd_ctx.ctx)
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goto out_unlock;
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if (dst_start < dst_vma->vm_start ||
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dst_start + len > dst_vma->vm_end)
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goto out_unlock;
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err = -EINVAL;
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if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
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goto out_unlock;
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vm_shared = dst_vma->vm_flags & VM_SHARED;
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}
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if (WARN_ON(dst_addr & (vma_hpagesize - 1) ||
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(len - copied) & (vma_hpagesize - 1)))
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goto out_unlock;
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/*
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* If not shared, ensure the dst_vma has a anon_vma.
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*/
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err = -ENOMEM;
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if (!vm_shared) {
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if (unlikely(anon_vma_prepare(dst_vma)))
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goto out_unlock;
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}
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h = hstate_vma(dst_vma);
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while (src_addr < src_start + len) {
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pte_t dst_pteval;
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BUG_ON(dst_addr >= dst_start + len);
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VM_BUG_ON(dst_addr & ~huge_page_mask(h));
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/*
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* Serialize via hugetlb_fault_mutex
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*/
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idx = linear_page_index(dst_vma, dst_addr);
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mapping = dst_vma->vm_file->f_mapping;
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hash = hugetlb_fault_mutex_hash(h, mapping, idx, dst_addr);
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mutex_lock(&hugetlb_fault_mutex_table[hash]);
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err = -ENOMEM;
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dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
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if (!dst_pte) {
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mutex_unlock(&hugetlb_fault_mutex_table[hash]);
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goto out_unlock;
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}
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err = -EEXIST;
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dst_pteval = huge_ptep_get(dst_pte);
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if (!huge_pte_none(dst_pteval)) {
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mutex_unlock(&hugetlb_fault_mutex_table[hash]);
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goto out_unlock;
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}
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err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
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dst_addr, src_addr, &page);
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mutex_unlock(&hugetlb_fault_mutex_table[hash]);
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vm_alloc_shared = vm_shared;
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cond_resched();
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if (unlikely(err == -ENOENT)) {
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up_read(&dst_mm->mmap_sem);
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BUG_ON(!page);
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err = copy_huge_page_from_user(page,
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(const void __user *)src_addr,
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pages_per_huge_page(h), true);
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if (unlikely(err)) {
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err = -EFAULT;
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goto out;
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}
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down_read(&dst_mm->mmap_sem);
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dst_vma = NULL;
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goto retry;
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} else
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BUG_ON(page);
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if (!err) {
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dst_addr += vma_hpagesize;
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src_addr += vma_hpagesize;
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copied += vma_hpagesize;
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if (fatal_signal_pending(current))
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err = -EINTR;
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}
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if (err)
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break;
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}
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out_unlock:
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up_read(&dst_mm->mmap_sem);
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out:
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if (page) {
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/*
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* We encountered an error and are about to free a newly
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* allocated huge page.
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*
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* Reservation handling is very subtle, and is different for
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* private and shared mappings. See the routine
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* restore_reserve_on_error for details. Unfortunately, we
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* can not call restore_reserve_on_error now as it would
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* require holding mmap_sem.
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*
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* If a reservation for the page existed in the reservation
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* map of a private mapping, the map was modified to indicate
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* the reservation was consumed when the page was allocated.
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* We clear the PagePrivate flag now so that the global
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* reserve count will not be incremented in free_huge_page.
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* The reservation map will still indicate the reservation
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* was consumed and possibly prevent later page allocation.
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* This is better than leaking a global reservation. If no
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* reservation existed, it is still safe to clear PagePrivate
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* as no adjustments to reservation counts were made during
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* allocation.
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*
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* The reservation map for shared mappings indicates which
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* pages have reservations. When a huge page is allocated
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* for an address with a reservation, no change is made to
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* the reserve map. In this case PagePrivate will be set
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* to indicate that the global reservation count should be
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* incremented when the page is freed. This is the desired
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* behavior. However, when a huge page is allocated for an
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* address without a reservation a reservation entry is added
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* to the reservation map, and PagePrivate will not be set.
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* When the page is freed, the global reserve count will NOT
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* be incremented and it will appear as though we have leaked
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* reserved page. In this case, set PagePrivate so that the
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* global reserve count will be incremented to match the
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* reservation map entry which was created.
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*
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* Note that vm_alloc_shared is based on the flags of the vma
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* for which the page was originally allocated. dst_vma could
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* be different or NULL on error.
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*/
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if (vm_alloc_shared)
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SetPagePrivate(page);
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else
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ClearPagePrivate(page);
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put_page(page);
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}
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BUG_ON(copied < 0);
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BUG_ON(err > 0);
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BUG_ON(!copied && !err);
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return copied ? copied : err;
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}
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#else /* !CONFIG_HUGETLB_PAGE */
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/* fail at build time if gcc attempts to use this */
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extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
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struct vm_area_struct *dst_vma,
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unsigned long dst_start,
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unsigned long src_start,
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unsigned long len,
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bool zeropage);
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#endif /* CONFIG_HUGETLB_PAGE */
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static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
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pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr,
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unsigned long src_addr,
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struct page **page,
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bool zeropage)
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{
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ssize_t err;
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/*
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* The normal page fault path for a shmem will invoke the
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* fault, fill the hole in the file and COW it right away. The
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* result generates plain anonymous memory. So when we are
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* asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
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* generate anonymous memory directly without actually filling
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* the hole. For the MAP_PRIVATE case the robustness check
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* only happens in the pagetable (to verify it's still none)
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* and not in the radix tree.
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*/
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if (!(dst_vma->vm_flags & VM_SHARED)) {
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if (!zeropage)
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err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
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dst_addr, src_addr, page);
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else
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err = mfill_zeropage_pte(dst_mm, dst_pmd,
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dst_vma, dst_addr);
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} else {
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if (!zeropage)
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err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
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dst_vma, dst_addr,
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src_addr, page);
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else
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err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd,
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dst_vma, dst_addr);
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}
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return err;
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}
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static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
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unsigned long dst_start,
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unsigned long src_start,
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unsigned long len,
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bool zeropage,
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bool *mmap_changing)
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{
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struct vm_area_struct *dst_vma;
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ssize_t err;
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pmd_t *dst_pmd;
|
|
unsigned long src_addr, dst_addr;
|
|
long copied;
|
|
struct page *page;
|
|
|
|
/*
|
|
* Sanitize the command parameters:
|
|
*/
|
|
BUG_ON(dst_start & ~PAGE_MASK);
|
|
BUG_ON(len & ~PAGE_MASK);
|
|
|
|
/* Does the address range wrap, or is the span zero-sized? */
|
|
BUG_ON(src_start + len <= src_start);
|
|
BUG_ON(dst_start + len <= dst_start);
|
|
|
|
src_addr = src_start;
|
|
dst_addr = dst_start;
|
|
copied = 0;
|
|
page = NULL;
|
|
retry:
|
|
down_read(&dst_mm->mmap_sem);
|
|
|
|
/*
|
|
* If memory mappings are changing because of non-cooperative
|
|
* operation (e.g. mremap) running in parallel, bail out and
|
|
* request the user to retry later
|
|
*/
|
|
err = -EAGAIN;
|
|
if (mmap_changing && READ_ONCE(*mmap_changing))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* Make sure the vma is not shared, that the dst range is
|
|
* both valid and fully within a single existing vma.
|
|
*/
|
|
err = -ENOENT;
|
|
dst_vma = find_vma(dst_mm, dst_start);
|
|
if (!dst_vma)
|
|
goto out_unlock;
|
|
/*
|
|
* Check the vma is registered in uffd, this is required to
|
|
* enforce the VM_MAYWRITE check done at uffd registration
|
|
* time.
|
|
*/
|
|
if (!dst_vma->vm_userfaultfd_ctx.ctx)
|
|
goto out_unlock;
|
|
|
|
if (dst_start < dst_vma->vm_start ||
|
|
dst_start + len > dst_vma->vm_end)
|
|
goto out_unlock;
|
|
|
|
err = -EINVAL;
|
|
/*
|
|
* shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
|
|
* it will overwrite vm_ops, so vma_is_anonymous must return false.
|
|
*/
|
|
if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
|
|
dst_vma->vm_flags & VM_SHARED))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* If this is a HUGETLB vma, pass off to appropriate routine
|
|
*/
|
|
if (is_vm_hugetlb_page(dst_vma))
|
|
return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
|
|
src_start, len, zeropage);
|
|
|
|
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* Ensure the dst_vma has a anon_vma or this page
|
|
* would get a NULL anon_vma when moved in the
|
|
* dst_vma.
|
|
*/
|
|
err = -ENOMEM;
|
|
if (!(dst_vma->vm_flags & VM_SHARED) &&
|
|
unlikely(anon_vma_prepare(dst_vma)))
|
|
goto out_unlock;
|
|
|
|
while (src_addr < src_start + len) {
|
|
pmd_t dst_pmdval;
|
|
|
|
BUG_ON(dst_addr >= dst_start + len);
|
|
|
|
dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
|
|
if (unlikely(!dst_pmd)) {
|
|
err = -ENOMEM;
|
|
break;
|
|
}
|
|
|
|
dst_pmdval = pmd_read_atomic(dst_pmd);
|
|
/*
|
|
* If the dst_pmd is mapped as THP don't
|
|
* override it and just be strict.
|
|
*/
|
|
if (unlikely(pmd_trans_huge(dst_pmdval))) {
|
|
err = -EEXIST;
|
|
break;
|
|
}
|
|
if (unlikely(pmd_none(dst_pmdval)) &&
|
|
unlikely(__pte_alloc(dst_mm, dst_pmd))) {
|
|
err = -ENOMEM;
|
|
break;
|
|
}
|
|
/* If an huge pmd materialized from under us fail */
|
|
if (unlikely(pmd_trans_huge(*dst_pmd))) {
|
|
err = -EFAULT;
|
|
break;
|
|
}
|
|
|
|
BUG_ON(pmd_none(*dst_pmd));
|
|
BUG_ON(pmd_trans_huge(*dst_pmd));
|
|
|
|
err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
|
|
src_addr, &page, zeropage);
|
|
cond_resched();
|
|
|
|
if (unlikely(err == -ENOENT)) {
|
|
void *page_kaddr;
|
|
|
|
up_read(&dst_mm->mmap_sem);
|
|
BUG_ON(!page);
|
|
|
|
page_kaddr = kmap(page);
|
|
err = copy_from_user(page_kaddr,
|
|
(const void __user *) src_addr,
|
|
PAGE_SIZE);
|
|
kunmap(page);
|
|
if (unlikely(err)) {
|
|
err = -EFAULT;
|
|
goto out;
|
|
}
|
|
goto retry;
|
|
} else
|
|
BUG_ON(page);
|
|
|
|
if (!err) {
|
|
dst_addr += PAGE_SIZE;
|
|
src_addr += PAGE_SIZE;
|
|
copied += PAGE_SIZE;
|
|
|
|
if (fatal_signal_pending(current))
|
|
err = -EINTR;
|
|
}
|
|
if (err)
|
|
break;
|
|
}
|
|
|
|
out_unlock:
|
|
up_read(&dst_mm->mmap_sem);
|
|
out:
|
|
if (page)
|
|
put_page(page);
|
|
BUG_ON(copied < 0);
|
|
BUG_ON(err > 0);
|
|
BUG_ON(!copied && !err);
|
|
return copied ? copied : err;
|
|
}
|
|
|
|
ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
|
|
unsigned long src_start, unsigned long len,
|
|
bool *mmap_changing)
|
|
{
|
|
return __mcopy_atomic(dst_mm, dst_start, src_start, len, false,
|
|
mmap_changing);
|
|
}
|
|
|
|
ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
|
|
unsigned long len, bool *mmap_changing)
|
|
{
|
|
return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing);
|
|
}
|