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| author | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-29 23:07:55 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-29 23:07:55 +0100 |
| commit | 5d2a2dbbc1025dbf7998b9289574d9592b8f21cc (patch) | |
| tree | b4f3f45190b814b5196235c21f983fbc7878a47b | |
| parent | VM: add common helper function to create the page tables (diff) | |
| download | linux-5d2a2dbbc1025dbf7998b9289574d9592b8f21cc.tar.xz linux-5d2a2dbbc1025dbf7998b9289574d9592b8f21cc.zip | |
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: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | mm/memory.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/memory.c b/mm/memory.c index 74f95ae0510b..745b3482e6c2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -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; |