From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id 9A63D6B0036 for ; Wed, 14 May 2014 23:38:50 -0400 (EDT) Received: by mail-pa0-f41.google.com with SMTP id lj1so485023pab.28 for ; Wed, 14 May 2014 20:38:50 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id ud7si3946259pab.40.2014.05.14.20.38.49 for ; Wed, 14 May 2014 20:38:49 -0700 (PDT) Date: Wed, 14 May 2014 20:38:59 -0700 From: Andrew Morton Subject: Re: [PATCH v2 -next] x86,vdso: Fix an OOPS accessing the hpet mapping w/o an hpet Message-Id: <20140514203859.8c82aa3a.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Hillf Danton Cc: Andy Lutomirski , x86@kernel.org, Sasha Levin , "linux-mm@kvack.org" , Dave Jones , LKML , Stefani Seibold On Thu, 15 May 2014 11:18:29 +0800 Hillf Danton wrote: > > --- a/arch/x86/vdso/vma.c > > +++ b/arch/x86/vdso/vma.c > > @@ -90,6 +90,7 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr) > > struct vm_area_struct *vma; > > unsigned long addr; > > int ret = 0; > > + static struct page *no_pages[] = {NULL}; > > > > if (calculate_addr) { > > addr = vdso_addr(current->mm->start_stack, > > @@ -125,7 +126,7 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr) > > addr + image->size, > > image->sym_end_mapping - image->size, > > VM_READ, > > - NULL); > > + no_pages); > > > > if (IS_ERR(vma)) { > > ret = PTR_ERR(vma); > > -- > > 1.9.0 > > > As the comment says, > /* > * Called with mm->mmap_sem held for writing. > * Insert a new vma covering the given region, with the given flags. > * Its pages are supplied by the given array of struct page *. > * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated. > * The region past the last page supplied will always produce SIGBUS. > * The array pointer and the pages it points to are assumed to stay alive > * for as long as this mapping might exist. > */ > struct vm_area_struct *_install_special_mapping(struct mm_struct *mm, > unsigned long addr, unsigned long len, > unsigned long vm_flags, struct page **pages) > { > > we can send sigbus at fault time if no pages are supplied at install time. Yes, but the way to communicate "no pages" is to pass (*pages)==NULL. Passing (pages)==NULL causes the code to oops at fault time. We could easily change the interface so that pages==NULL means "no pages" but that isn't the way it works at present. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org