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| author | Hugh Dickins <hugh@veritas.com> | 2005-11-21 21:32:18 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-22 09:13:42 -0800 |
| commit | ee498ed730283e9cdfc8913f12b90a2246f1a8cc (patch) | |
| tree | 797966a8454e40fdf1879bacea510ad8c55a91a2 /mm/rmap.c | |
| parent | 920fc356f58d0e455bdfa53451f1c58eb211a846 (diff) | |
| download | lwn-ee498ed730283e9cdfc8913f12b90a2246f1a8cc.tar.gz lwn-ee498ed730283e9cdfc8913f12b90a2246f1a8cc.zip | |
[PATCH] unpaged: anon in VM_UNPAGED
copy_one_pte needs to copy the anonymous COWed pages in a VM_UNPAGED area,
zap_pte_range needs to free them, do_wp_page needs to COW them: just like
ordinary pages, not like the unpaged.
But recognizing them is a little subtle: because PageReserved is no longer a
condition for remap_pfn_range, we can now mmap all of /dev/mem (whether the
distro permits, and whether it's advisable on this or that architecture, is
another matter). So if we can see a PageAnon, it may not be ours to mess with
(or may be ours from elsewhere in the address space). I suspect there's an
entertaining insoluble self-referential problem here, but the page_is_anon
function does a good practical job, and MAP_PRIVATE PROT_WRITE VM_UNPAGED will
always be an odd choice.
In updating the comment on page_address_in_vma, noticed a potential NULL
dereference, in a path we don't actually take, but fixed it.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index 377d417ec15f..2e034a0b89ab 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -225,7 +225,9 @@ vma_address(struct page *page, struct vm_area_struct *vma) /* * At what user virtual address is page expected in vma? checking that the - * page matches the vma: currently only used by unuse_process, on anon pages. + * page matches the vma: currently only used on anon pages, by unuse_vma; + * and by extraordinary checks on anon pages in VM_UNPAGED vmas, taking + * care that an mmap of /dev/mem might window free and foreign pages. */ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) { @@ -234,7 +236,8 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) (void *)page->mapping - PAGE_MAPPING_ANON) return -EFAULT; } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { - if (vma->vm_file->f_mapping != page->mapping) + if (!vma->vm_file || + vma->vm_file->f_mapping != page->mapping) return -EFAULT; } else return -EFAULT; |