[PATCH] mlock-vs-VM_IO hang fix
With Andrea Arcangeli <andrea@novell.com> Fix a hang which occurs when mlock() encounters a mapping of /dev/mem. These have VM_IO set. follow_page() keeps returning zero (not a valid pfn) and handle_mm_fault() keeps on returning VM_FAULT_MINOR (there's a pte there), so get_user_pages() locks up. The patch changes get_user_pages() to just bale out when it hits a VM_IO region. make_pages_present() is taught to ignore the resulting -EFAULT. We still have two bugs: a) If a process has a VM_IO vma, get_user_pages() will bale early, without having considered the vmas at higher virtual addresses. As do_mlock() also walks the vma list this bug is fairly benign, but get_user_pages() is doing the wrong thing there. b) The `len' argument to get_user_pages should be long, not int. We presently have a 16TB limit on 64-bit. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Showing
Please register or sign in to comment