From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932708AbbFRRx1 (ORCPT ); Thu, 18 Jun 2015 13:53:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47628 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932431AbbFRRxR (ORCPT ); Thu, 18 Jun 2015 13:53:17 -0400 Date: Thu, 18 Jun 2015 19:52:07 +0200 From: Oleg Nesterov To: Al Viro , Andrew Morton , Benjamin LaHaise , Jeff Moyer Cc: linux-aio@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 1/3] aio_ring_remap: kill the bogus ctx->dead check Message-ID: <20150618175207.GA10055@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150618175143.GA10033@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kill_ioctx() sets ctx->dead and removes ctx from ->ioctx_table "atomically" under mm->ioctx_lock, so aio_ring_remap() can never see a dead ctx. And even -EINVAL doesn't look necessary. Yes, if mremap() races with kill_ioctx() vm_munmap(ctx->mmap_base, ctx->mmap_size) can unmap the wrong region. In this case the buggy application should blame itself. And there are other reasons why that vm_munmap() can be wrong. Say, an application can mremap() the part of aio region and then do io_destroy(). We could change aio_ring_remap() to verify vma->that vma_end - vma->vma_start == ctx->mmap_size but this won't help if the application does munmap() instead. Signed-off-by: Oleg Nesterov --- fs/aio.c | 9 +++------ 1 files changed, 3 insertions(+), 6 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 480440f..893d300 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -325,14 +325,11 @@ static int aio_ring_remap(struct file *file, struct vm_area_struct *vma) rcu_read_lock(); table = rcu_dereference(mm->ioctx_table); for (i = 0; i < table->nr; i++) { - struct kioctx *ctx; + struct kioctx *ctx = table->table[i]; - ctx = table->table[i]; if (ctx && ctx->aio_ring_file == file) { - if (!atomic_read(&ctx->dead)) { - ctx->user_id = ctx->mmap_base = vma->vm_start; - res = 0; - } + ctx->user_id = ctx->mmap_base = vma->vm_start; + res = 0; break; } } -- 1.5.5.1