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Mon, 01 Jun 2026 11:55:48 -0700 (PDT) Received: from ALA-EXCHNG02.corp.ad.wrs.com (10.11.224.122) by ala-exchng01.corp.ad.wrs.com (10.11.224.121) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.61; Mon, 1 Jun 2026 11:55:46 -0700 Received: from c38b02c5ee49.wrs.com (10.11.232.110) by ALA-EXCHNG02.corp.ad.wrs.com (10.11.224.122) with Microsoft SMTP Server id 15.1.2507.61 via Frontend Transport; Mon, 1 Jun 2026 11:55:45 -0700 From: Yun Zhou To: , CC: , , Subject: [PATCH] ublk: fix null-ptr-deref in ublk_queue_cmd Date: Tue, 2 Jun 2026 02:55:43 +0800 Message-ID: <20260601185544.1180263-1-yun.zhou@windriver.com> X-Mailer: git-send-email 2.48.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjAxMDE4NiBTYWx0ZWRfX9S/ZkuiZtfi0 RNN8V1ABwUHGGkwj57T6lPcTjd/hf3aPchdGlx2gPBwD9JrATh27QjlHzgF2NERvRXS04X7WSQO 7pdpyDgSr8aXKIOHXl5jrpq4QCLu6rXod0Fx7HCosPhWTn16z8fTTy8y8r3Dzf3F4jkUx/bioDV fitoLLgOnghM1FKstE74Oo+TjbUbHMaGYPEOyZZWdx/GwAJB//sb/eSlU06BBO8nuuvhjrx33Rx 75SXHdheG0+OwqfwXY2L8EAdbmzfweTn3TngRVXa+tFMWv9bNDyGWvQ8sZE9pQiKv5IYMqZ53W3 5SLzVDmtN+dYbNREN2qMcoLWhW15Qq+l7fK80QrDofdDmhuT+daLYwjo0of3auYG+6OwpEGehy/ oDqRpUBGzcmfpvZgbS+qKm5a0AQd6AEp4fPaPyRlFKmrWT6x+DfwoHHggb46qG5enFcgRLdxo84 mJO6rPTQh7JTyah+/0Q== X-Proofpoint-GUID: TSUX0mV6r5MkXFqM7vozdV-KFP2b_MTm X-Authority-Analysis: v=2.4 cv=Iq0utr/g c=1 sm=1 tr=0 ts=6a1dd5b4 cx=c_pps a=AbJuCvi4Y3V6hpbCNWx0WA==:117 a=AbJuCvi4Y3V6hpbCNWx0WA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=bi6dqmuHe4P4UrxVR6um:22 a=iKiJcTA2PjBS6x5JeXcw:22 a=edf1wS77AAAA:8 a=hSkVLCK3AAAA:8 a=t7CeM3EgAAAA:8 a=nFqGxSASerJtwWmRO4wA:9 a=DcSpbTIhAlouE1Uv7lRv:22 a=cQPPKAXgyycSBL8etih5:22 a=FdTzh2GWekK77mhwV6Dw:22 X-Proofpoint-ORIG-GUID: TSUX0mV6r5MkXFqM7vozdV-KFP2b_MTm X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-01_05,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 adultscore=0 priorityscore=1501 clxscore=1011 malwarescore=0 impostorscore=0 suspectscore=0 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606010186 Content-Type: text/plain; charset="utf-8" ublk_queue_cmd() dereferences ios[tag].cmd without NULL check. The cmd pointer can be NULL when ublk_cancel_cmd() races with IO dispatch during server teardown: CPU0 (partition scan work) CPU1 (io_uring cancel callback) ublk_queue_rq() ublk_prep_req() -> OK check canceling -> false ublk_start_cancel() quiesce, set canceling, unquiesce ublk_cancel_cmd() io->cmd =3D NULL ublk_queue_cmd() cmd =3D ios[tag].cmd -> NULL ublk_get_uring_cmd_pdu(cmd) -> null-ptr-deref The race window exists because ublk_cancel_cmd() can execute between the canceling flag check and the cmd dereference in ublk_queue_cmd(). This cannot be closed with simple synchronization since blk_mq_quiesce_queue only waits for in-flight dispatches, not requests already past the canceling check. Fix by checking cmd for NULL before dereferencing. When NULL, abort the request via __ublk_abort_rq() which handles both recovery (requeue) and non-recovery (end with IOERR) cases. Fixes: 71f28f3136af ("ublk_drv: add io_uring based userspace block driver") Reported-by: syzbot+415b9ec753cd2a196087@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D415b9ec753cd2a196087 Signed-off-by: Yun Zhou --- drivers/block/ublk_drv.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 6c041eaebdb9..656e0d4e92bb 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -2090,8 +2090,14 @@ static void ublk_batch_queue_cmd(struct ublk_queue *= ubq, struct request *rq, boo static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq) { struct io_uring_cmd *cmd =3D ubq->ios[rq->tag].cmd; - struct ublk_uring_cmd_pdu *pdu =3D ublk_get_uring_cmd_pdu(cmd); + struct ublk_uring_cmd_pdu *pdu; + + if (unlikely(!cmd)) { + __ublk_abort_rq(ubq, rq); + return; + } =20 + pdu =3D ublk_get_uring_cmd_pdu(cmd); pdu->req =3D rq; io_uring_cmd_complete_in_task(cmd, ublk_cmd_tw_cb); } --=20 2.43.0