linux-kernel - [PATCH AUTOSEL for 3.18 37/59] target/iscsi: Fix a race condition in iscsit_add_reject_from

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Date:   Thu, 7 Dec 2017 15:51:31 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Bart Van Assche <bart.vanassche@....com>,
        Christoph Hellwig <hch@....de>,
        Mike Christie <mchristi@...hat.com>,
        Nicholas Bellinger <nab@...ux-iscsi.org>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 3.18 37/59] target/iscsi: Fix a race condition in
 iscsit_add_reject_from_cmd()

From: Bart Van Assche <bart.vanassche@....com>

[ Upstream commit cfe2b621bb18d86e93271febf8c6e37622da2d14 ]

Avoid that cmd->se_cmd.se_tfo is read after a command has already been
freed.

Signed-off-by: Bart Van Assche <bart.vanassche@....com>
Cc: Christoph Hellwig <hch@....de>
Cc: Mike Christie <mchristi@...hat.com>
Reviewed-by: Hannes Reinecke <hare@...e.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/target/iscsi/iscsi_target.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index f0ace220753e..9582f082152c 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -674,6 +674,7 @@ static int iscsit_add_reject_from_cmd(
 	unsigned char *buf)
 {
 	struct iscsi_conn *conn;
+	const bool do_put = cmd->se_cmd.se_tfo != NULL;
 
 	if (!cmd->conn) {
 		pr_err("cmd->conn is NULL for ITT: 0x%08x\n",
@@ -704,7 +705,7 @@ static int iscsit_add_reject_from_cmd(
 	 * Perform the kref_put now if se_cmd has already been setup by
 	 * scsit_setup_scsi_cmd()
 	 */
-	if (cmd->se_cmd.se_tfo != NULL) {
+	if (do_put) {
 		pr_debug("iscsi reject: calling target_put_sess_cmd >>>>>>\n");
 		target_put_sess_cmd(&cmd->se_cmd);
 	}
-- 
2.11.0