4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andrea Arcangeli <aarca...@redhat.com> [ Upstream commit 6bbc4a4144b1a69743022ac68dfaf6e7d993abb9 ] __do_fault assumes vmf->page has been initialized and is valid if VM_FAULT_NOPAGE is not returned by vma->vm_ops->fault(vma, vmf). handle_userfault() in turn should return VM_FAULT_NOPAGE if it doesn't return VM_FAULT_SIGBUS or VM_FAULT_RETRY (the other two possibilities). This VM_FAULT_NOPAGE case is only invoked when signal are pending and it didn't matter for anonymous memory before. It only started to matter since shmem was introduced. hugetlbfs also takes a different path and doesn't exercise __do_fault. Link: http://lkml.kernel.org/r/20170228154201.gh5...@redhat.com Signed-off-by: Andrea Arcangeli <aarca...@redhat.com> Reported-by: Dmitry Vyukov <dvyu...@google.com> Cc: "Kirill A. Shutemov" <kir...@shutemov.name> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Sasha Levin <alexander.le...@verizon.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- fs/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -386,7 +386,7 @@ int handle_userfault(struct vm_area_stru * in such case. */ down_read(&mm->mmap_sem); - ret = 0; + ret = VM_FAULT_NOPAGE; } }
