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Mon, 3 Nov 2025 11:19:16 +0000 (GMT) Date: Mon, 3 Nov 2025 12:19:15 +0100 From: Heiko Carstens To: Duoming Zhou , Jan Hoeppner Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, mingo@kernel.org, tglx@linutronix.de Subject: Re: [PATCH] s390/tape: fix use-after-free bugs caused by tape_dnr delayed work Message-ID: <20251103111915.18191A14-hca@linux.ibm.com> References: <20251103060544.22720-1-duoming@zju.edu.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251103060544.22720-1-duoming@zju.edu.cn> X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=StmdKfO0 c=1 sm=1 tr=0 ts=69088fba cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=pBTJcwekMGGDtO02zGIA:9 a=CjuIK1q_8ugA:10 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-ORIG-GUID: 3byK_aW4tFw9iyp-MNLo4HpiuD2-nlTX X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTAxMDAxOCBTYWx0ZWRfX0Nqianh8vm6P JvxIhmJeOVTzihQvYUcF56bO5l29G2qtZ31gzHExTor5jpDzgois9J11zAgW7FasMhxMAOe589A v3cOdX+ULeDkKWfoJVPCfghtgRvEnaUeY6rjVc97kndVsYWaQAo1WpxOazMjFNIAq9A4+q5znoY T1eOsGhADtzPgKED/wrO3Z9A6cOTEw4AaaU4lJGZo9j41ywYUTuEdKML2LVTkz+EowB/SZFdsp7 hDe99SS4k+9okuYCzZmrg5kQuw1Jg2L6DuH9it35w9vatTpg14xtfXD+Uzmt3aj6gK0+MFlKDtE 7wcgkNaMpqJfrZbDyiGVt0qeDnZv7xT72rUvKc0p+aweaxJKhvVkJ6QNiz3MyGOEDilP02JPNyT LMmskc6q60tewCJ1iylwKgEuZ4cCEg== X-Proofpoint-GUID: 3byK_aW4tFw9iyp-MNLo4HpiuD2-nlTX X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-03_01,2025-10-29_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 phishscore=0 impostorscore=0 priorityscore=1501 malwarescore=0 clxscore=1011 adultscore=0 bulkscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511010018 [full quote below - adding Jan] On Mon, Nov 03, 2025 at 02:05:44PM +0800, Duoming Zhou wrote: > The delayed work tape_dnr is initialized in tape_alloc_device(), which > is called from tape_generic_probe(), and is scheduled in the following > scenarios: > > 1. Starting an I/O operation fails with -EBUSY in __tape_start_io(). > 2. Canceling an I/O operation fails with -EBUSY in __tape_cancel_io(). > 3. A deferred error condition is detected in __tape_do_irq(). > > When the tape device is detached via tape_generic_remove(), the > tape_device structure might be deallocated after the final call to > tape_put_device(). However, if the delayed work tape_dnr is still > pending or executing at the time of detachment, it could lead to > use-after-free bugs when the work function tape_delayed_next_request() > accesses the already freed tape_device memory. > > The race condition can occur as follows: > > CPU 0(detach thread) | CPU 1 (delayed work) > tape_generic_remove() | > tape_put_device(device) | tape_delayed_next_request > | device = container_of(...) // USE > | device-> // USE > > Add disable_delayed_work_sync() in tape_generic_remove() to guarantee > proper cancellation of the delayed work item before tape_device is > deallocated. > > This bug is identified by static analysis. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Duoming Zhou > --- > drivers/s390/char/tape_core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/s390/char/tape_core.c b/drivers/s390/char/tape_core.c > index 6ec812280221..722dc4737a87 100644 > --- a/drivers/s390/char/tape_core.c > +++ b/drivers/s390/char/tape_core.c > @@ -625,6 +625,7 @@ tape_generic_remove(struct ccw_device *cdev) > } > DBF_LH(3, "(%08x): tape_generic_remove(%p)\n", device->cdev_id, cdev); > > + disable_delayed_work_sync(&device->tape_dnr); > spin_lock_irq(get_ccwdev_lock(device->cdev)); > switch (device->tape_state) { > case TS_INIT: Jan, could you please have a look at this?