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Commit 5d2a2dbb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

cow_user_page: fix page alignment 



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: default avatarLinus Torvalds <torvalds@osdl.org>
parent c9cfcddf

mm/memory.c

+9 −2
Original line number Diff line number Diff line
@@ -1394,8 +1394,15 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo 
	 */

	if (unlikely(!src)) {

		void *kaddr = kmap_atomic(dst, KM_USER0);

		unsigned long left = __copy_from_user_inatomic(kaddr, (void __user *)va, PAGE_SIZE);

		if (left)

		void __user *uaddr = (void __user *)(va & PAGE_MASK);



		/*

		 * 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);

		kunmap_atomic(kaddr, KM_USER0);

		return;