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Mon, 3 Aug 2026 18:20:54 +0000 (GMT) From: Nagamani PV To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: horms@kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, wintera@linux.ibm.com, twinkler@linux.ibm.com, heiko.carstens@de.ibm.com, hidayath@linux.ibm.com, borntraeger@linux.ibm.com, stable@vger.kernel.org Subject: [PATCH net-next] net/iucv: fix UAF in afiucv_netdev_event() Date: Mon, 3 Aug 2026 20:20:53 +0200 Message-ID: <20260803182053.2355882-1-nagamani@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwODAzMDE2MiBTYWx0ZWRfX7Vw8xPl3LY/1 Z2r+U7gdivjl438T5lb9jzMZIZcHNiYFTFNwv2yN0rnPl6RClnAAKVfFQFIvSDln9FVF94noUKz SWp4gMisorgpAsFQZ1t3M59xJulGwN0= X-Authority-Analysis: v=2.4 cv=I7VVgtgg c=1 sm=1 tr=0 ts=6a70dc0c cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=9erWuH-dJbx6lHhtDFoA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAzMDE2MiBTYWx0ZWRfX0Trovc4+qUDe QQdcFFqKCsvCrkjBO4FWbbA+4ohC+Z+vARGTvaSmK1mLis5VqaIALexKIyXYBaeCn/Tt5W/H52q 2eZNwwTe6+qbH0CK6eVMv310d30G6P/7i1841q90Ru7+RY8XVytUBENHYt9SSfe7RlfNJoF5rln Pz5doQbD63p2295D7jakFAiadU0daDGtl4962+fMpODoglD7CJOQZU5+PqjzCRORPYnEWly4UtZ DP06ymjt63K76UZmi8zHD6EAKvv0Pnkkr0zKjhVDUih2yeauB9L+7xhJYRu9e69xPGIXKnyok4X 8brZ/lng7gzHL6a3hnoliiWp+c1pBo5Mql5jJAi3ASD7jTxAuBTyOrWyROlSITHz/nt585cJsEj 15gK7dFOC4va7si0FJXz0gWjtdDeo+J2zepfu1wQ1BIVc8Vw61hDprPENP661Ak9E7pI9XpDwyT WcWXpF70xpi+m8niN9A== X-Proofpoint-ORIG-GUID: RKENEiIK7HTDh2HKB9m3NaR-nxu4k1jT X-Proofpoint-GUID: MzUuTnwLBFT2u-rvelEiNoq-Dc2PfjLZ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-03_04,2026-08-03_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 impostorscore=0 clxscore=1011 priorityscore=1501 suspectscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608030162 afiucv_netdev_event() traverses iucv_sk_list without holding iucv_sk_list.lock. A concurrent socket teardown can unlink and free an af_iucv socket via iucv_sock_kill() while the netdevice notifier path is still traversing the list, resulting in a use-after-free when dereferencing the socket. syzbot reported a KASAN slab-use-after-free triggered from the netdevice notifier path: BUG: KASAN: slab-use-after-free in afiucv_netdev_event+0x166/0x570 Read of size 8 at addr 001a54009dcda368 by task syz.3.24/516 Call Trace: afiucv_netdev_event+0x166/0x570 net/iucv/af_iucv.c:2193 notifier_call_chain+0x18e/0x510 kernel/notifier.c:85 call_netdevice_notifiers net/core/dev.c:2301 [inline] __dev_close_many+0x1c6/0x680 net/core/dev.c:1747 unregister_netdevice_many_notify+0x9b6/0x2650 net/core/dev.c:12388 unregister_netdevice_queue+0x392/0x3d0 net/core/dev.c:12291 __tun_detach+0xa50/0x1990 drivers/net/tun.c:621 Allocated by task 521: sk_prot_alloc+0xd2/0x230 net/core/sock.c:2247 sk_alloc+0x48/0x680 net/core/sock.c:2303 iucv_sock_alloc+0x4e/0x710 net/iucv/af_iucv.c:456 iucv_sock_create+0x114/0x180 net/iucv/af_iucv.c:2254 Freed by task 519: kfree+0x164/0x500 mm/slub.c:6561 iucv_sock_release+0x12e/0x150 net/iucv/af_iucv.c:1482 sock_close+0xa4/0x230 net/socket.c:1514 Protect the list traversal with the existing read-side lock. Use read_lock_bh()/read_unlock_bh() to synchronize with write_lock_bh()-protected updates to iucv_sk_list. Fixes: 9fbd87d41392 ("af_iucv: handle netdev events") Cc: stable@vger.kernel.org Suggested-by: Hidayath Khan Signed-off-by: Nagamani PV --- net/iucv/af_iucv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c index ea047bab65e7..034039c50941 100644 --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -2213,6 +2213,7 @@ static int afiucv_netdev_event(struct notifier_block *this, switch (event) { case NETDEV_REBOOT: case NETDEV_GOING_DOWN: + read_lock_bh(&iucv_sk_list.lock); sk_for_each(sk, &iucv_sk_list.head) { iucv = iucv_sk(sk); if ((iucv->hs_dev == event_dev) && @@ -2223,6 +2224,7 @@ static int afiucv_netdev_event(struct notifier_block *this, sk->sk_state_change(sk); } } + read_unlock_bh(&iucv_sk_list.lock); break; case NETDEV_DOWN: case NETDEV_UNREGISTER: -- 2.53.0