> > it used to be MAP_NR(page) earlier which was of course wrong. but
> > vaddr can come from userspace (read/write a raw device),
>
> It should be quite safe. kiobufs should always refer to kernel
> addresses, not user addresses. If you do a map_user_kiobuf(), the user
> pages will already have been converted into kernel virtual addresses and
> the appropriate pages pinned in memory. (That's what the follow_page()
> is for before map_user_kiobuf calls get_page_map().)
we do
map = follow_page(ptr);
to convert the userspace vaddr to a struct page *. right ?
where is it converted to a kernel virtual address ? if ptr already was a
kernel address, then we should have simply done
map = mem_map + MAP_NR(ptr).
then we do
map = get_page_map(map, ptr);
and now we pass this to get_page_map() which promptly returns 0, so
map = 0.
it's quite easy to hit this, just try reading a raw device.
ganesh
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This archive was generated by hypermail 2b29 : Tue Mar 07 2000 - 21:00:11 EST