From: Yu Kuai <yukuai1@huaweicloud.com> To: Christoph Hellwig <hch@lst.de>, Yu Kuai <yukuai1@huaweicloud.com> Cc: Jens Axboe <axboe@kernel.dk>, Alasdair Kergon <agk@redhat.com>, Mike Snitzer <snitzer@kernel.org>, dm-devel@redhat.com, linux-block@vger.kernel.org, "yukuai (C)" <yukuai3@huawei.com> Subject: Re: [PATCH 7/7] block: store the holder kobject in bd_holder_disk Date: Tue, 1 Nov 2022 19:12:51 +0800 [thread overview] Message-ID: <d3f6ec1d-8141-19d1-ce4c-d42710f4a636@huaweicloud.com> (raw) In-Reply-To: <20221101104927.GA13823@lst.de> Hi, 在 2022/11/01 18:49, Christoph Hellwig 写道: > On Mon, Oct 31, 2022 at 09:52:04AM +0800, Yu Kuai wrote: >>> INIT_LIST_HEAD(&holder->list); >>> - holder->bdev = bdev; >>> holder->refcnt = 1; >>> + holder->holder_dir = kobject_get(bdev->bd_holder_dir); >> >> I wonder is this safe here, if kobject reference is 0 here and >> bd_holder_dir is about to be freed. Here in kobject_get, kref_get() will >> warn about uaf, and kobject_get will return a address that is about to >> be freed. > > But how could the reference be 0 here? The driver that calls > bd_link_disk_holder must have the block device open and thus hold a > reference to it. Like I said before, the caller of bd_link_disk_holder() get bdev by blkdev_get_by_dev(), which do not grab reference of holder_dir, and grab disk reference can only prevent disk_release() to be called, not del_gendisk() while holder_dir reference is dropped in del_gendisk() and can be decreased to 0. If you agree with above explanation, I tried to fix this: 1) move kobject_put(bd_holder_dir) from del_gendisk to disk_release, there seems to be a lot of other dependencies. 2) protect bd_holder_dir reference by open_mutex. Thanks, Kuai > > . >
WARNING: multiple messages have this Message-ID (diff)
From: Yu Kuai <yukuai1@huaweicloud.com> To: Christoph Hellwig <hch@lst.de>, Yu Kuai <yukuai1@huaweicloud.com> Cc: Jens Axboe <axboe@kernel.dk>, Mike Snitzer <snitzer@kernel.org>, linux-block@vger.kernel.org, dm-devel@redhat.com, "yukuai \(C\)" <yukuai3@huawei.com>, Alasdair Kergon <agk@redhat.com> Subject: Re: [dm-devel] [PATCH 7/7] block: store the holder kobject in bd_holder_disk Date: Tue, 1 Nov 2022 19:12:51 +0800 [thread overview] Message-ID: <d3f6ec1d-8141-19d1-ce4c-d42710f4a636@huaweicloud.com> (raw) In-Reply-To: <20221101104927.GA13823@lst.de> Hi, 在 2022/11/01 18:49, Christoph Hellwig 写道: > On Mon, Oct 31, 2022 at 09:52:04AM +0800, Yu Kuai wrote: >>> INIT_LIST_HEAD(&holder->list); >>> - holder->bdev = bdev; >>> holder->refcnt = 1; >>> + holder->holder_dir = kobject_get(bdev->bd_holder_dir); >> >> I wonder is this safe here, if kobject reference is 0 here and >> bd_holder_dir is about to be freed. Here in kobject_get, kref_get() will >> warn about uaf, and kobject_get will return a address that is about to >> be freed. > > But how could the reference be 0 here? The driver that calls > bd_link_disk_holder must have the block device open and thus hold a > reference to it. Like I said before, the caller of bd_link_disk_holder() get bdev by blkdev_get_by_dev(), which do not grab reference of holder_dir, and grab disk reference can only prevent disk_release() to be called, not del_gendisk() while holder_dir reference is dropped in del_gendisk() and can be decreased to 0. If you agree with above explanation, I tried to fix this: 1) move kobject_put(bd_holder_dir) from del_gendisk to disk_release, there seems to be a lot of other dependencies. 2) protect bd_holder_dir reference by open_mutex. Thanks, Kuai > > . > -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2022-11-01 11:12 UTC|newest] Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-30 15:31 fix delayed holder tracking v2 Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-30 15:31 ` [PATCH 1/7] block: clear ->slave_dir when dropping the main slave_dir reference Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-30 15:31 ` [PATCH 2/7] dm: remove free_table_devices Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-30 15:31 ` [PATCH 3/7] dm: cleanup open_table_device Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-30 15:31 ` [PATCH 4/7] dm: cleanup close_table_device Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-30 15:31 ` [PATCH 5/7] dm: track per-add_disk holder relations in DM Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-11-09 2:08 ` Yu Kuai 2022-11-09 2:08 ` [dm-devel] " Yu Kuai 2022-11-09 8:26 ` Christoph Hellwig 2022-11-09 8:26 ` [dm-devel] " Christoph Hellwig 2022-11-10 18:09 ` Mike Snitzer 2022-11-10 18:09 ` [dm-devel] " Mike Snitzer 2022-11-10 19:48 ` Mike Snitzer 2022-11-10 19:48 ` Mike Snitzer 2022-11-12 6:23 ` Yu Kuai 2022-11-12 6:23 ` [dm-devel] " Yu Kuai 2022-10-30 15:31 ` [PATCH 6/7] block: remove delayed holder registration Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-30 15:31 ` [PATCH 7/7] block: store the holder kobject in bd_holder_disk Christoph Hellwig 2022-10-30 15:31 ` [dm-devel] " Christoph Hellwig 2022-10-31 1:52 ` Yu Kuai 2022-10-31 1:52 ` [dm-devel] " Yu Kuai 2022-11-01 10:49 ` Christoph Hellwig 2022-11-01 10:49 ` [dm-devel] " Christoph Hellwig 2022-11-01 11:12 ` Yu Kuai [this message] 2022-11-01 11:12 ` Yu Kuai 2022-11-01 11:21 ` Christoph Hellwig 2022-11-01 11:21 ` [dm-devel] " Christoph Hellwig 2022-11-01 11:28 ` Yu Kuai 2022-11-01 11:28 ` [dm-devel] " Yu Kuai 2022-11-01 13:18 ` Christoph Hellwig 2022-11-01 13:18 ` [dm-devel] " Christoph Hellwig 2022-11-01 13:29 ` Yu Kuai 2022-11-01 13:29 ` [dm-devel] " Yu Kuai
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