From: Christoph Hellwig <hch@infradead.org> To: "Matias Bjørling" <m@bjorling.me> Cc: Christoph Hellwig <hch@infradead.org>, LKML <linux-kernel@vger.kernel.org>, "linux-block@vger.kernel.org" <linux-block@vger.kernel.org> Subject: Re: BUG: KASAN: Use-after-free Date: Tue, 24 Jan 2017 01:52:09 -0800 [thread overview] Message-ID: <20170124095209.GA22003@infradead.org> (raw) In-Reply-To: <400b4572-0994-8950-582b-c3372333f6c8@bjorling.me> 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 (;;) {
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org> To: "Matias Bjørling" <m@bjorling.me> Cc: Christoph Hellwig <hch@infradead.org>, LKML <linux-kernel@vger.kernel.org>, "linux-block@vger.kernel.org" <linux-block@vger.kernel.org> Subject: Re: BUG: KASAN: Use-after-free Date: Tue, 24 Jan 2017 01:52:09 -0800 [thread overview] Message-ID: <20170124095209.GA22003@infradead.org> (raw) In-Reply-To: <400b4572-0994-8950-582b-c3372333f6c8@bjorling.me> 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 (;;) {
next prev parent reply other threads:[~2017-01-24 9:52 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-01-23 16:07 BUG: KASAN: Use-after-free Matias Bjørling 2017-01-23 17:20 ` Christoph Hellwig 2017-01-23 17:20 ` Christoph Hellwig 2017-01-24 9:32 ` Matias Bjørling 2017-01-24 9:32 ` Matias Bjørling 2017-01-24 9:52 ` Christoph Hellwig [this message] 2017-01-24 9:52 ` Christoph Hellwig 2017-01-24 10:01 ` Matias Bjørling 2017-01-24 10:01 ` Matias Bjørling 2017-01-24 13:34 ` Christoph Hellwig 2017-01-24 13:34 ` Christoph Hellwig 2017-01-24 13:37 ` Matias Bjørling 2017-01-24 13:37 ` Matias Bjørling
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