From 6bbc4a4144b1a69743022ac68dfaf6e7d993abb9 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 9 Mar 2017 16:16:28 -0800 Subject: [PATCH] userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE __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.GH5816@redhat.com Signed-off-by: Andrea Arcangeli Reported-by: Dmitry Vyukov Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 973607df579d..f62199b90fd0 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -490,7 +490,7 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason) * in such case. */ down_read(&mm->mmap_sem); - ret = 0; + ret = VM_FAULT_NOPAGE; } } -- GitLab