From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754760Ab2GIOpS (ORCPT ); Mon, 9 Jul 2012 10:45:18 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:38216 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754402Ab2GIOiL (ORCPT ); Mon, 9 Jul 2012 10:38:11 -0400 Message-Id: <20120709143123.229568316@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 09 Jul 2012 15:32:02 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Andy Lutomirski , Hugh Dickins , Miklos Szeredi , Badari Pulavarty , Nick Piggin Subject: [ 46/48] mm: Hold a file reference in madvise_remove In-Reply-To: <20120709143116.348975190@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit 9ab4233dd08036fe34a89c7dc6f47a8bf2eb29eb upstream. Otherwise the code races with munmap (causing a use-after-free of the vma) or with close (causing a use-after-free of the struct file). The bug was introduced by commit 90ed52ebe481 ("[PATCH] holepunch: fix mmap_sem i_mutex deadlock") Cc: Hugh Dickins Cc: Miklos Szeredi Cc: Badari Pulavarty Cc: Nick Piggin Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: - Adjust context - madvise_remove() calls vmtruncate_range(), not do_fallocate()] Signed-off-by: Ben Hutchings --- mm/madvise.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) --- a/mm/madvise.c +++ b/mm/madvise.c @@ -13,6 +13,7 @@ #include #include #include +#include /* * Any behaviour which results in changes to the vma->vm_flags needs to @@ -197,14 +198,16 @@ static long madvise_remove(struct vm_are struct address_space *mapping; loff_t offset, endoff; int error; + struct file *f; *prev = NULL; /* tell sys_madvise we drop mmap_sem */ if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) return -EINVAL; - if (!vma->vm_file || !vma->vm_file->f_mapping - || !vma->vm_file->f_mapping->host) { + f = vma->vm_file; + + if (!f || !f->f_mapping || !f->f_mapping->host) { return -EINVAL; } @@ -218,9 +221,16 @@ static long madvise_remove(struct vm_are endoff = (loff_t)(end - vma->vm_start - 1) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); - /* vmtruncate_range needs to take i_mutex */ + /* + * vmtruncate_range may need to take i_mutex. We need to + * explicitly grab a reference because the vma (and hence the + * vma's reference to the file) can go away as soon as we drop + * mmap_sem. + */ + get_file(f); up_read(¤t->mm->mmap_sem); error = vmtruncate_range(mapping->host, offset, endoff); + fput(f); down_read(¤t->mm->mmap_sem); return error; }