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Wed, 23 Sep 2026 00:10:29 -0700 (PDT) Received: from flow.bytedance.net ([203.208.167.150]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc75f3bae00sm643835a12.10.2026.09.23.00.10.26 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 23 Sep 2026 00:10:28 -0700 (PDT) From: By To: song@kernel.org, yukuai@fygo.io Cc: magiclinan@didiglobal.com, xiao@kernel.org, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, By , syzbot+95eeb4ada2349a2170ea@syzkaller.appspotmail.com Subject: [PATCH] md: prevent opening an array before its sysfs kobject is ready Date: Wed, 23 Sep 2026 15:10:17 +0800 Message-ID: <20260923071017.23563-1-xiaobai050@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit md_alloc() publishes the gendisk with add_disk() before it initializes and registers mddev->kobj. A concurrent open can issue ADD_NEW_DISK in this window, causing bind_rdev_to_array() to pass the uninitialized mddev kobject as a parent to kobject_add(). This triggers a kobject warning. Set MD_CLOSING before publishing the disk so md_open() rejects opens until the kobject and sysfs attributes are ready. Clear the bit under open_mutex, which md_open() holds while checking it. Compile-tested with ARCH=arm64 defconfig and drivers/md/md.o. The upstream syzbot report has no reproducer, so this race was not tested at runtime. Fixes: 7df835a32a8b ("md: fix a lock order reversal in md_alloc") Reported-by: syzbot+95eeb4ada2349a2170ea@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=95eeb4ada2349a2170ea Assisted-by: LLM Signed-off-by: By --- drivers/md/md.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index 680b34a63..11b0b6b13 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6385,6 +6385,8 @@ struct mddev *md_alloc(dev_t dev, char *name) disk->events |= DISK_EVENT_MEDIA_CHANGE; mddev->gendisk = disk; + /* add_disk() exposes the device before its md kobject is registered. */ + set_bit(MD_CLOSING, &mddev->flags); error = add_disk(disk); if (error) goto out_put_disk; @@ -6406,6 +6408,9 @@ struct mddev *md_alloc(dev_t dev, char *name) kobject_uevent(&mddev->kobj, KOBJ_ADD); mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, "array_state"); mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, "level"); + mutex_lock(&mddev->open_mutex); + clear_bit(MD_CLOSING, &mddev->flags); + mutex_unlock(&mddev->open_mutex); mutex_unlock(&disks_mutex); return mddev; -- 2.55.0