From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([65.50.211.133]:55512 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750707AbdAXJwK (ORCPT ); Tue, 24 Jan 2017 04:52:10 -0500 Date: Tue, 24 Jan 2017 01:52:09 -0800 From: Christoph Hellwig To: Matias =?iso-8859-1?Q?Bj=F8rling?= Cc: Christoph Hellwig , LKML , "linux-block@vger.kernel.org" Subject: Re: BUG: KASAN: Use-after-free Message-ID: <20170124095209.GA22003@infradead.org> References: <0b458b92-62ee-bffc-8f3e-fbd6490b26fd@bjorling.me> <20170123172021.GA28446@infradead.org> <400b4572-0994-8950-582b-c3372333f6c8@bjorling.me> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <400b4572-0994-8950-582b-c3372333f6c8@bjorling.me> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Tue, Jan 24, 2017 at 10:32:11AM +0100, Matias Bj�rling wrote: > *(gdb) list *blkdev_direct_IO+0x50c > 0xffffffff8142ab8c is in blkdev_direct_IO (fs/block_dev.c:401). > 396 submit_bio(bio); > 397 bio = bio_alloc(GFP_KERNEL, nr_pages); > 398 } > 399 blk_finish_plug(&plug); > 400 > 401 if (!dio->is_sync) > 402 return -EIOCBQUEUED; > > It looks like the qc = submit_bio() completes the I/O before the > blkdev_direct_IO completes, which then leads to the use after free case, > when the private dio struct is accessed. Ok, the is_sync check here is clearly a bug, we need a local variable for is_sync as well for the aio case: diff --git a/fs/block_dev.c b/fs/block_dev.c index 5db5d13..3c47614 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -331,7 +331,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) struct blk_plug plug; struct blkdev_dio *dio; struct bio *bio; - bool is_read = (iov_iter_rw(iter) == READ); + bool is_read = (iov_iter_rw(iter) == READ), is_sync; loff_t pos = iocb->ki_pos; blk_qc_t qc = BLK_QC_T_NONE; int ret; @@ -344,7 +344,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) bio_get(bio); /* extra ref for the completion handler */ dio = container_of(bio, struct blkdev_dio, bio); - dio->is_sync = is_sync_kiocb(iocb); + dio->is_sync = is_sync = is_sync_kiocb(iocb); if (dio->is_sync) dio->waiter = current; else @@ -398,7 +398,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) } blk_finish_plug(&plug); - if (!dio->is_sync) + if (!is_sync) return -EIOCBQUEUED; for (;;) { From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750775AbdAXJwM (ORCPT ); Tue, 24 Jan 2017 04:52:12 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:55512 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750707AbdAXJwK (ORCPT ); Tue, 24 Jan 2017 04:52:10 -0500 Date: Tue, 24 Jan 2017 01:52:09 -0800 From: Christoph Hellwig To: Matias =?iso-8859-1?Q?Bj=F8rling?= Cc: Christoph Hellwig , LKML , "linux-block@vger.kernel.org" Subject: Re: BUG: KASAN: Use-after-free Message-ID: <20170124095209.GA22003@infradead.org> References: <0b458b92-62ee-bffc-8f3e-fbd6490b26fd@bjorling.me> <20170123172021.GA28446@infradead.org> <400b4572-0994-8950-582b-c3372333f6c8@bjorling.me> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <400b4572-0994-8950-582b-c3372333f6c8@bjorling.me> User-Agent: Mutt/1.7.1 (2016-10-04) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 24, 2017 at 10:32:11AM +0100, Matias Bjørling wrote: > *(gdb) list *blkdev_direct_IO+0x50c > 0xffffffff8142ab8c is in blkdev_direct_IO (fs/block_dev.c:401). > 396 submit_bio(bio); > 397 bio = bio_alloc(GFP_KERNEL, nr_pages); > 398 } > 399 blk_finish_plug(&plug); > 400 > 401 if (!dio->is_sync) > 402 return -EIOCBQUEUED; > > It looks like the qc = submit_bio() completes the I/O before the > blkdev_direct_IO completes, which then leads to the use after free case, > when the private dio struct is accessed. Ok, the is_sync check here is clearly a bug, we need a local variable for is_sync as well for the aio case: diff --git a/fs/block_dev.c b/fs/block_dev.c index 5db5d13..3c47614 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -331,7 +331,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) struct blk_plug plug; struct blkdev_dio *dio; struct bio *bio; - bool is_read = (iov_iter_rw(iter) == READ); + bool is_read = (iov_iter_rw(iter) == READ), is_sync; loff_t pos = iocb->ki_pos; blk_qc_t qc = BLK_QC_T_NONE; int ret; @@ -344,7 +344,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) bio_get(bio); /* extra ref for the completion handler */ dio = container_of(bio, struct blkdev_dio, bio); - dio->is_sync = is_sync_kiocb(iocb); + dio->is_sync = is_sync = is_sync_kiocb(iocb); if (dio->is_sync) dio->waiter = current; else @@ -398,7 +398,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) } blk_finish_plug(&plug); - if (!dio->is_sync) + if (!is_sync) return -EIOCBQUEUED; for (;;) {