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[128.210.106.74]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-13fca8df89asm13408224c88.9.2026.08.04.14.37.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2026 14:37:11 -0700 (PDT) From: Yifei Gao To: "Martin K . Petersen" , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org Cc: Mike Christie , linux-kernel@vger.kernel.org, Yifei Gao , stable@vger.kernel.org Subject: [PATCH] scsi: target: tcm_fc: use kref_get_unless_zero() in ft_sess_get() Date: Tue, 4 Aug 2026 21:37:02 +0000 Message-ID: <20260804213703.3411166-1-gyf161023@gmail.com> X-Mailer: git-send-email 2.43.0 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 Content-Type: text/plain; charset="utf-8" ft_sess_get() walks the RCU-protected session hash under rcu_read_lock() and takes a plain kref_get() on a matching session. Session teardown does hlist_del_rcu() and then drops ft_lport_lock before the final ft_sess_put() -> kfree_rcu(). A reader that is preempted between the port_id comparison and the kref_get() can therefore revive a session whose refcount has already dropped to zero and is pending free, leading to a use-after-free and a double target_remove_session(). Use kref_get_unless_zero() and treat a zero refcount as "not found", matching the standard pattern for RCU lookups that race with kref-based teardown. Fixes: 3699d92a4d7b ("[SCSI] tcm_fc: Adding FC_FC4 provider (tcm_fc) for FC= oE target (TCM - target core) support") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Yifei Gao --- drivers/target/tcm_fc/tfc_sess.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/target/tcm_fc/tfc_sess.c b/drivers/target/tcm_fc/tfc_s= ess.c index 797be06ab71b..1bc7d2dcbea3 100644 --- a/drivers/target/tcm_fc/tfc_sess.c +++ b/drivers/target/tcm_fc/tfc_sess.c @@ -172,7 +172,8 @@ static struct ft_sess *ft_sess_get(struct fc_lport *lpo= rt, u32 port_id) head =3D &tport->hash[ft_sess_hash(port_id)]; hlist_for_each_entry_rcu(sess, head, hash) { if (sess->port_id =3D=3D port_id) { - kref_get(&sess->kref); + if (!kref_get_unless_zero(&sess->kref)) + break; rcu_read_unlock(); TFC_SESS_DBG(lport, "port_id %x found %p\n", port_id, sess); --=20 2.43.0