linux-kernel - [PATCH AUTOSEL 5.10 029/217] scsi: target: Fix cmd

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Date:   Tue, 22 Dec 2020 21:13:18 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>,
        Himanshu Madhani <himanshu.madhani@...cle.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>, linux-scsi@...r.kernel.org,
        target-devel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 029/217] scsi: target: Fix cmd_count ref leak

From: Mike Christie <michael.christie@...cle.com>

[ Upstream commit 02dd4914b0bcb8fd8f8cad9817f5715a17466261 ]

percpu_ref_init sets the refcount to 1 and percpu_ref_kill drops it.
Drivers like iSCSI and loop do not call target_sess_cmd_list_set_waiting
during session shutdown, though, so they have been calling percpu_ref_exit
with a refcount still taken and leaking the cmd_counts memory.

Link: https://lore.kernel.org/r/1604257174-4524-3-git-send-email-michael.christie@oracle.com
Reviewed-by: Himanshu Madhani <himanshu.madhani@...cle.com>
Signed-off-by: Mike Christie <michael.christie@...cle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/target/target_core_transport.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ff26ab0a5f600..d47619a5d172e 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -238,6 +238,14 @@ EXPORT_SYMBOL(transport_init_session);
 
 void transport_uninit_session(struct se_session *se_sess)
 {
+	/*
+	 * Drivers like iscsi and loop do not call
+	 * target_sess_cmd_list_set_waiting during session shutdown so we
+	 * have to drop the ref taken at init time here.
+	 */
+	if (!se_sess->sess_tearing_down)
+		percpu_ref_put(&se_sess->cmd_count);
+
 	percpu_ref_exit(&se_sess->cmd_count);
 }
 
-- 
2.27.0