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authorHugh Dickins <hugh@veritas.com>2005-11-21 21:32:18 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-22 09:13:42 -0800
commitee498ed730283e9cdfc8913f12b90a2246f1a8cc (patch)
tree797966a8454e40fdf1879bacea510ad8c55a91a2 /mm/rmap.c
parent920fc356f58d0e455bdfa53451f1c58eb211a846 (diff)
downloadlwn-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.c7
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;