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![Christian Brauner](/assets/img/avatar_default.png)
The inode_owner_or_capable() helper determines whether the caller is the owner of the inode or is capable with respect to that inode. Allow it to handle idmapped mounts. If the inode is accessed through an idmapped mount it according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Similarly, allow the inode_init_owner() helper to handle idmapped mounts. It initializes a new inode on idmapped mounts by mapping the fsuid and fsgid of the caller from the mount's user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
281 lines
7 KiB
C
281 lines
7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/mincore.c
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*
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* Copyright (C) 1994-2006 Linus Torvalds
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*/
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/*
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* The mincore() system call.
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*/
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#include <linux/pagemap.h>
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#include <linux/gfp.h>
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#include <linux/pagewalk.h>
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#include <linux/mman.h>
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#include <linux/syscalls.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/shmem_fs.h>
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#include <linux/hugetlb.h>
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#include <linux/pgtable.h>
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#include <linux/uaccess.h>
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static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
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unsigned long end, struct mm_walk *walk)
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{
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#ifdef CONFIG_HUGETLB_PAGE
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unsigned char present;
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unsigned char *vec = walk->private;
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/*
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* Hugepages under user process are always in RAM and never
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* swapped out, but theoretically it needs to be checked.
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*/
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present = pte && !huge_pte_none(huge_ptep_get(pte));
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for (; addr != end; vec++, addr += PAGE_SIZE)
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*vec = present;
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walk->private = vec;
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#else
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BUG();
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#endif
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return 0;
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}
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/*
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* Later we can get more picky about what "in core" means precisely.
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* For now, simply check to see if the page is in the page cache,
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* and is up to date; i.e. that no page-in operation would be required
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* at this time if an application were to map and access this page.
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*/
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static unsigned char mincore_page(struct address_space *mapping, pgoff_t index)
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{
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unsigned char present = 0;
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struct page *page;
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/*
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* When tmpfs swaps out a page from a file, any process mapping that
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* file will not get a swp_entry_t in its pte, but rather it is like
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* any other file mapping (ie. marked !present and faulted in with
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* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
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*/
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page = find_get_incore_page(mapping, index);
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if (page) {
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present = PageUptodate(page);
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put_page(page);
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}
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return present;
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}
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static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
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struct vm_area_struct *vma, unsigned char *vec)
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{
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unsigned long nr = (end - addr) >> PAGE_SHIFT;
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int i;
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if (vma->vm_file) {
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pgoff_t pgoff;
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pgoff = linear_page_index(vma, addr);
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for (i = 0; i < nr; i++, pgoff++)
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vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
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} else {
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for (i = 0; i < nr; i++)
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vec[i] = 0;
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}
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return nr;
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}
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static int mincore_unmapped_range(unsigned long addr, unsigned long end,
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__always_unused int depth,
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struct mm_walk *walk)
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{
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walk->private += __mincore_unmapped_range(addr, end,
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walk->vma, walk->private);
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return 0;
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}
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static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
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struct mm_walk *walk)
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{
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spinlock_t *ptl;
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struct vm_area_struct *vma = walk->vma;
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pte_t *ptep;
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unsigned char *vec = walk->private;
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int nr = (end - addr) >> PAGE_SHIFT;
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ptl = pmd_trans_huge_lock(pmd, vma);
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if (ptl) {
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memset(vec, 1, nr);
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spin_unlock(ptl);
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goto out;
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}
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if (pmd_trans_unstable(pmd)) {
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__mincore_unmapped_range(addr, end, vma, vec);
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goto out;
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}
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ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
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for (; addr != end; ptep++, addr += PAGE_SIZE) {
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pte_t pte = *ptep;
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if (pte_none(pte))
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__mincore_unmapped_range(addr, addr + PAGE_SIZE,
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vma, vec);
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else if (pte_present(pte))
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*vec = 1;
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else { /* pte is a swap entry */
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swp_entry_t entry = pte_to_swp_entry(pte);
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if (non_swap_entry(entry)) {
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/*
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* migration or hwpoison entries are always
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* uptodate
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*/
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*vec = 1;
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} else {
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#ifdef CONFIG_SWAP
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*vec = mincore_page(swap_address_space(entry),
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swp_offset(entry));
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#else
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WARN_ON(1);
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*vec = 1;
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#endif
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}
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}
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vec++;
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}
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pte_unmap_unlock(ptep - 1, ptl);
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out:
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walk->private += nr;
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cond_resched();
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return 0;
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}
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static inline bool can_do_mincore(struct vm_area_struct *vma)
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{
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if (vma_is_anonymous(vma))
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return true;
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if (!vma->vm_file)
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return false;
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/*
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* Reveal pagecache information only for non-anonymous mappings that
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* correspond to the files the calling process could (if tried) open
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* for writing; otherwise we'd be including shared non-exclusive
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* mappings, which opens a side channel.
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*/
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return inode_owner_or_capable(&init_user_ns,
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file_inode(vma->vm_file)) ||
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file_permission(vma->vm_file, MAY_WRITE) == 0;
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}
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static const struct mm_walk_ops mincore_walk_ops = {
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.pmd_entry = mincore_pte_range,
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.pte_hole = mincore_unmapped_range,
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.hugetlb_entry = mincore_hugetlb,
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};
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/*
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* Do a chunk of "sys_mincore()". We've already checked
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* all the arguments, we hold the mmap semaphore: we should
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* just return the amount of info we're asked for.
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*/
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static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
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{
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struct vm_area_struct *vma;
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unsigned long end;
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int err;
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vma = find_vma(current->mm, addr);
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if (!vma || addr < vma->vm_start)
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return -ENOMEM;
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end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
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if (!can_do_mincore(vma)) {
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unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
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memset(vec, 1, pages);
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return pages;
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}
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err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
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if (err < 0)
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return err;
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return (end - addr) >> PAGE_SHIFT;
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}
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/*
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* The mincore(2) system call.
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*
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* mincore() returns the memory residency status of the pages in the
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* current process's address space specified by [addr, addr + len).
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* The status is returned in a vector of bytes. The least significant
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* bit of each byte is 1 if the referenced page is in memory, otherwise
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* it is zero.
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*
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* Because the status of a page can change after mincore() checks it
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* but before it returns to the application, the returned vector may
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* contain stale information. Only locked pages are guaranteed to
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* remain in memory.
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*
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* return values:
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* zero - success
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* -EFAULT - vec points to an illegal address
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* -EINVAL - addr is not a multiple of PAGE_SIZE
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* -ENOMEM - Addresses in the range [addr, addr + len] are
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* invalid for the address space of this process, or
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* specify one or more pages which are not currently
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* mapped
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* -EAGAIN - A kernel resource was temporarily unavailable.
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*/
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SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
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unsigned char __user *, vec)
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{
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long retval;
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unsigned long pages;
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unsigned char *tmp;
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start = untagged_addr(start);
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/* Check the start address: needs to be page-aligned.. */
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if (start & ~PAGE_MASK)
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return -EINVAL;
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/* ..and we need to be passed a valid user-space range */
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if (!access_ok((void __user *) start, len))
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return -ENOMEM;
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/* This also avoids any overflows on PAGE_ALIGN */
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pages = len >> PAGE_SHIFT;
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pages += (offset_in_page(len)) != 0;
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if (!access_ok(vec, pages))
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return -EFAULT;
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tmp = (void *) __get_free_page(GFP_USER);
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if (!tmp)
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return -EAGAIN;
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retval = 0;
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while (pages) {
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/*
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* Do at most PAGE_SIZE entries per iteration, due to
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* the temporary buffer size.
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*/
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mmap_read_lock(current->mm);
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retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
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mmap_read_unlock(current->mm);
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if (retval <= 0)
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break;
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if (copy_to_user(vec, tmp, retval)) {
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retval = -EFAULT;
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break;
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}
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pages -= retval;
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vec += retval;
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start += retval << PAGE_SHIFT;
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retval = 0;
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}
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free_page((unsigned long) tmp);
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return retval;
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}
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