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cow_user_page: fix page alignment

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High Dickins points out that the user virtual address passed to the page
fault handler isn't necessarily page-aligned.

Also, add a comment on why the copy could fail for the user address case.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Linus Torvalds 2005-11-29 14:07:55 -08:00
parent c9cfcddfd6
commit 5d2a2dbbc1
1 changed files with 9 additions and 2 deletions
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11
mm/memory.c
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@ -1394,8 +1394,15 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo
*/ */
if (unlikely(!src)) { if (unlikely(!src)) {
void *kaddr = kmap_atomic(dst, KM_USER0); void *kaddr = kmap_atomic(dst, KM_USER0);
unsigned long left = __copy_from_user_inatomic(kaddr, (void __user *)va, PAGE_SIZE); void __user *uaddr = (void __user *)(va & PAGE_MASK);
if (left)
/*
* This really shouldn't fail, because the page is there
* in the page tables. But it might just be unreadable,
* in which case we just give up and fill the result with
* zeroes.
*/
if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
memset(kaddr, 0, PAGE_SIZE); memset(kaddr, 0, PAGE_SIZE);
kunmap_atomic(kaddr, KM_USER0); kunmap_atomic(kaddr, KM_USER0);
return; return;