On Mon, Apr 15, 2013 at 2:47 PM, Hugh Dickins <hu...@google.com> wrote:
> --- 3.9-rc7/mm/mlock.c 2013-04-01 09:08:05.736012852 -0700
> +++ linux/mm/mlock.c 2013-04-15 14:20:24.454773245 -0700
> @@ -397,8 +397,7 @@ int __mm_populate(unsigned long start, u
> long ret = 0;
>
> VM_BUG_ON(start & ~PAGE_MASK);
> - VM_BUG_ON(len != PAGE_ALIGN(len));
> - end = start + len;
> + end = start + PAGE_ALIGN(len);
>
> for (nstart = start; nstart < end; nstart = nend) {
> /*
Yes, there was originally an issue with page alignment in mmap as well, which
was fixed by making sure mmap now passes the page aligned length to
mm_populate().
sys_brk() passes the length as the difference of two page aligned addresses, so
it's fine. But vm_brk() doesn't - it calls do_brk() which page aligns the
length, but then vm_brk passes the unaligned length to mm_populate().
What do you think of the following ? len is already a PAGE_SIZE multiple when
called from sys_brk()...
diff --git a/mm/mmap.c b/mm/mmap.c
index 0db0de1c2fbe..6af8b0d1c7db 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2557,10 +2557,6 @@ static unsigned long do_brk(unsigned long addr, unsigned
long len)
pgoff_t pgoff = addr >> PAGE_SHIFT;
int error;
- len = PAGE_ALIGN(len);
- if (!len)
- return addr;
-
flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
@@ -2643,6 +2639,10 @@ unsigned long vm_brk(unsigned long addr, unsigned long
len)
unsigned long ret;
bool populate;
+ len = PAGE_ALIGN(len);
+ if (!len)
+ return addr;
+
down_write(&mm->mmap_sem);
ret = do_brk(addr, len);
populate = ((mm->def_flags & VM_LOCKED) != 0);
--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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