4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andrea Arcangeli <[email protected]> [ 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/[email protected] Signed-off-by: Andrea Arcangeli <[email protected]> Reported-by: Dmitry Vyukov <[email protected]> Cc: "Kirill A. Shutemov" <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -419,7 +419,7 @@ int handle_userfault(struct fault_env *f * in such case. */ down_read(&mm->mmap_sem); - ret = 0; + ret = VM_FAULT_NOPAGE; } }
