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Fri, 7 Aug 2026 08:16:14 +0000 (GMT) Received: by tuxmaker.boeblingen.de.ibm.com (Postfix, from userid 56341) id CAD99160DFC; Fri, 07 Aug 2026 10:16:14 +0200 (CEST) From: Mahanta Jambigi To: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, alibuda@linux.alibaba.com, dust.li@linux.alibaba.com, sidraya@linux.ibm.com Cc: pasic@linux.ibm.com, horms@kernel.org, tonylu@linux.alibaba.com, guwen@linux.alibaba.com, netdev@vger.kernel.org, linux-s390@vger.kernel.org, Mahanta Jambigi Subject: [PATCH net v3] net/smc: fix clcsock and lgr/lnk races in smc_diag dump path Date: Fri, 7 Aug 2026 10:16:04 +0200 Message-ID: <20260807081606.3200128-1-mjambigi@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA3MDA1NyBTYWx0ZWRfXx4Y43Akhefun 24sBYsMLeKFO4WujLbDetqXVRGnKPWJf5lh4cbaQJ72Py8eYGqU4HcKnen4KJ2hZUzk5ZEHAnVG BMGLaNc2EaGxxpDHGJqP3IhGBUDaPiLOXAsKWShbuK+zqQEVknOdVXI/iPkfqXr9p5JcQUOEYXJ 7sO6O4I9alQ118XKdGDszoS/4ZCgVtgW4Y8kT991x7ZGod0DiE8OjtCKH7yuJ43ZWNl2FzkM9UY OkdoWZDgNmJgU44cUsiQTATGAz04wJ2kU1CAotPruly9tsbYqrxkLXyXAv+kimCLkAWxMZsv6K4 nDk2d8GsG2ChVqlWbueo9lFqqlYDKiQMe9O58aCu4ywtl6EjkNVCh2hixccHds51Lz4EaABumDy eOgUezznOtIGOeHEfpIhAgPEGUUyAC+2Lb1vdjO3xO3dJcthfAzWak7hC5VJN6OYH7YCnY6DlG3 0QCPMVBAqafwVXZ0v5Q== X-Proofpoint-ORIG-GUID: N-gexsGQoPS_Cu7dchBsN5xiW4UrsWqJ X-Proofpoint-GUID: sHUUdkfmuf19Xa13JQm1Pbrtr-Evabz1 X-Proofpoint-Spam-Info: AW1haW4tMjYwODA3MDA1NyBTYWx0ZWRfX3bo0LicR6M7C vaOvGXVbC5/Eoknxi55gcJqmzn3NFbJAWy0TSQleZI/M+4unVjtyeEiaXawh/ghuha3tiWeRvhI 1GXlHpuEky4iVrFZGpXoNnUmO6KWryc= X-Authority-Analysis: v=2.4 cv=WLpPmHsR c=1 sm=1 tr=0 ts=6a759455 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=ChcJzeUvlmU10I9KIo8A:9 a=QEXdDO2ut3YA:10 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=2026-08-07_01,2026-08-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 adultscore=0 malwarescore=0 clxscore=1011 impostorscore=0 priorityscore=1501 phishscore=0 suspectscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608070057 Two races in the SMC diag dump path: Race 1: smc_diag_msg_common_fill() reads smc->clcsock fields after a NULL check, but smc_clcsock_release() can set clcsock =3D NULL under clcsock_release_lock between the check and the reads. Hold the same mutex in the read path to make the check and reads atomic. Race 2: __smc_diag_dump() dereferences conn->lgr and conn->lnk with no protection against concurrent teardown. smc_close_active_abort() calls smc_conn_free() =E2=80=94 which drops lgr and link refcounts =E2=80=94 wi= thout first unhashing the socket, leaving stale pointers visible to the dump. The teardown path holds lock_sock(sk) across smc_conn_free(); take the same lock in __smc_diag_dump() to serialise fully. Both fixes require sleeping locks, which are illegal under the read_lock(&smc_hash->lock) held by smc_diag_dump_proto(). Pin each socket with refcount_inc_not_zero() before dropping the hash lock, call __smc_diag_dump() locklessly, then release the pin. Restart sk_for_each(= ) from head after each unlock rather than resuming mid-walk: smc_unhash_sk() nulls sk->sk_node.next via sk_del_node_init(), so resuming an interrupted walk silently truncates the dump. Fixes: f16a7dd5cf27 ("smc: netlink interface for SMC sockets") Fixes: 9dbe086c69b8 ("net/smc: fix invalid link access in dumping SMC-R c= onnections") Reviewed-by: Sidraya Jayagond Signed-off-by: Mahanta Jambigi --- net/smc/smc_diag.c | 78 +++++++++++++++++++++++++++++++++++---------- 1 file changed, 61 insertions(+), 17 deletions(-) diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c index bf0beaa23bdb..000000000000 100644 --- a/net/smc/smc_diag.c +++ b/net/smc/smc_diag.c @@ -39,22 +39,34 @@ memset(r, 0, sizeof(*r)); r->diag_family =3D sk->sk_family; sock_diag_save_cookie(sk, r->id.idiag_cookie); - if (!smc->clcsock) - return; - r->id.idiag_sport =3D htons(smc->clcsock->sk->sk_num); - r->id.idiag_dport =3D smc->clcsock->sk->sk_dport; - r->id.idiag_if =3D smc->clcsock->sk->sk_bound_dev_if; - if (sk->sk_protocol =3D=3D SMCPROTO_SMC) { - r->id.idiag_src[0] =3D smc->clcsock->sk->sk_rcv_saddr; - r->id.idiag_dst[0] =3D smc->clcsock->sk->sk_daddr; + /* + * smc_clcsock_release() sets smc->clcsock =3D NULL under + * clcsock_release_lock before freeing the socket. Hold the same + * mutex here to make the NULL check and all field reads atomic + * with that writer. mutex_lock() is safe: this function is called + * only after the hash spinlock has been dropped by + * smc_diag_dump_proto(). + */ + mutex_lock(&smc->clcsock_release_lock); + if (smc->clcsock) { + r->id.idiag_sport =3D htons(smc->clcsock->sk->sk_num); + r->id.idiag_dport =3D smc->clcsock->sk->sk_dport; + r->id.idiag_if =3D smc->clcsock->sk->sk_bound_dev_if; + if (sk->sk_protocol =3D=3D SMCPROTO_SMC) { + r->id.idiag_src[0] =3D smc->clcsock->sk->sk_rcv_saddr; + r->id.idiag_dst[0] =3D smc->clcsock->sk->sk_daddr; #if IS_ENABLED(CONFIG_IPV6) - } else if (sk->sk_protocol =3D=3D SMCPROTO_SMC6) { - memcpy(&r->id.idiag_src, &smc->clcsock->sk->sk_v6_rcv_saddr, - sizeof(smc->clcsock->sk->sk_v6_rcv_saddr)); - memcpy(&r->id.idiag_dst, &smc->clcsock->sk->sk_v6_daddr, - sizeof(smc->clcsock->sk->sk_v6_daddr)); + } else if (sk->sk_protocol =3D=3D SMCPROTO_SMC6) { + memcpy(&r->id.idiag_src, + &smc->clcsock->sk->sk_v6_rcv_saddr, + sizeof(smc->clcsock->sk->sk_v6_rcv_saddr)); + memcpy(&r->id.idiag_dst, + &smc->clcsock->sk->sk_v6_daddr, + sizeof(smc->clcsock->sk->sk_v6_daddr)); #endif + } } + mutex_unlock(&smc->clcsock_release_lock); } =20 static int smc_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb, @@ -87,6 +99,15 @@ =20 r =3D nlmsg_data(nlh); smc_diag_msg_common_fill(r, sk); + /* + * Take the socket lock to serialise against smc_conn_free(), + * which drops lgr and link refcounts under lock_sock(). Without + * this, a concurrent close can free lgr->lnk[] memory between + * our smc_conn_lgr_valid() check and the subsequent lgr/lnk + * dereferences. lock_sock() is safe here because the hash + * spinlock has been dropped by smc_diag_dump_proto(). + */ + lock_sock(sk); r->diag_state =3D sk->sk_state; if (smc->use_fallback) r->diag_mode =3D SMC_DIAG_MODE_FALLBACK_TCP; @@ -182,13 +203,16 @@ dinfo.peer_token =3D conn->peer_token; =20 if (nla_put(skb, SMC_DIAG_DMBINFO, sizeof(dinfo), &dinfo) < 0) goto errout; } =20 + release_sock(sk); + nlmsg_end(skb, nlh); return 0; =20 errout: + release_sock(sk); nlmsg_cancel(skb, nlh); return -EMSGSIZE; } @@ -204,25 +228,43 @@ int rc =3D 0, num =3D 0; struct sock *sk; =20 - read_lock(&prot->h.smc_hash->lock); head =3D &prot->h.smc_hash->ht; +restart: + num =3D 0; + read_lock(&prot->h.smc_hash->lock); if (hlist_empty(head)) goto out; - sk_for_each(sk, head) { if (!net_eq(sock_net(sk), net)) continue; if (num < snum) goto next; + /* + * Pin sk before dropping the lock. refcount_inc_not_zero() + * skips sockets already past their last reference. + * smc_unhash_sk() nulls sk->sk_node.next via sk_del_node_init() + * so resuming an interrupted sk_for_each() would terminate + * early if a socket is unhashed while the lock is dropped. + * Restart from head after each unlock, using snum to skip + * already-dumped entries. + */ + if (!refcount_inc_not_zero(&sk->sk_refcnt)) + goto next; + read_unlock(&prot->h.smc_hash->lock); + rc =3D __smc_diag_dump(sk, skb, cb, nlmsg_data(cb->nlh), bc); + sock_put(sk); + if (rc < 0) - goto out; + goto out_nolock; + snum =3D num + 1; + goto restart; next: num++; } - out: read_unlock(&prot->h.smc_hash->lock); +out_nolock: cb_ctx->pos[p_type] =3D num; return rc; } --=20 2.50.1