From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Leon Romanovsky <leonro@nvidia.com>,
	Mike Christie <michael.christie@oracle.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.1 370/609] scsi: target: Clear cmd_cnt when initial counter enrollment fails
Date: Mon, 17 Aug 2026 15:31:06 +0200
Message-ID: <20260817132556.665251843@linuxfoundation.org>
In-Reply-To: <20260817132543.039278408@linuxfoundation.org>
References: <20260817132543.039278408@linuxfoundation.org>
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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Leon Romanovsky <leonro@nvidia.com>

[ Upstream commit a8ddfd2425bbbafadae8700d63ed8a61a4109878 ]

When target_get_sess_cmd() fails during session shutdown because
percpu_ref_tryget_live() returns false, the command keeps the
se_cmd->cmd_cnt pointer that __target_init_cmd() assigned earlier
without owning a reference. Final release through
target_release_cmd_kref() then issues an unmatched percpu_ref_put().

Commit 8e288be8606a ("scsi: target: Pass in cmd counter to use during
cmd setup") moved the cmd_cnt assignment ahead of the reference
acquisition.  Clear se_cmd->cmd_cnt whenever the initial
target_get_sess_cmd() fails in target_init_cmd() and
target_submit_tmr(), so release performs exactly one matching put per
acquired reference.

Fixes: 8e288be8606a ("scsi: target: Pass in cmd counter to use during cmd setup")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Link: https://patch.msgid.link/20260722-reference-count-underflow-in-target-v1-1-63ab664f12fd@nvidia.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/target/target_core_transport.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index b9a144a59dff3..f4e3ba173dbe3 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1670,6 +1670,7 @@ int target_init_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
 		    u32 data_length, int task_attr, int data_dir, int flags)
 {
 	struct se_portal_group *se_tpg;
+	int ret;
 
 	se_tpg = se_sess->se_tpg;
 	BUG_ON(!se_tpg);
@@ -1699,7 +1700,11 @@ int target_init_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
 	 * necessary for fabrics using TARGET_SCF_ACK_KREF that expect a second
 	 * kref_put() to happen during fabric packet acknowledgement.
 	 */
-	return target_get_sess_cmd(se_cmd, flags & TARGET_SCF_ACK_KREF);
+	ret = target_get_sess_cmd(se_cmd, flags & TARGET_SCF_ACK_KREF);
+	if (ret)
+		se_cmd->cmd_cnt = NULL;
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(target_init_cmd);
 
@@ -1994,8 +1999,10 @@ int target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
 	 * allocation failure.
 	 */
 	ret = core_tmr_alloc_req(se_cmd, fabric_tmr_ptr, tm_type, gfp);
-	if (ret < 0)
+	if (ret < 0) {
+		se_cmd->cmd_cnt = NULL;
 		return -ENOMEM;
+	}
 
 	if (tm_type == TMR_ABORT_TASK)
 		se_cmd->se_tmr_req->ref_task_tag = tag;
@@ -2003,6 +2010,7 @@ int target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
 	/* See target_submit_cmd for commentary */
 	ret = target_get_sess_cmd(se_cmd, flags & TARGET_SCF_ACK_KREF);
 	if (ret) {
+		se_cmd->cmd_cnt = NULL;
 		core_tmr_release_req(se_cmd->se_tmr_req);
 		return ret;
 	}
-- 
2.53.0