[PATCH 5.15 42/75] scsi: target: iscsi: Fix use-after-free in iscsit_dec_conn_usage_count()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Maurizio Lombardi <mlombard@redhat.com>

[ Upstream commit 9411a89e9e7135cc459178fa77a3f1d6191ae903 ]

In iscsit_dec_conn_usage_count(), the function calls complete() while
holding the conn->conn_usage_lock. As soon as complete() is invoked, the
waiter (such as iscsit_close_connection()) may wake up and proceed to free
the iscsit_conn structure.

If the waiter frees the memory before the current thread reaches
spin_unlock_bh(), it results in a KASAN slab-use-after-free as the function
attempts to release a lock within the already-freed connection structure.

Fix this by releasing the spinlock before calling complete().

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reported-by: Zhaojuan Guo <zguo@redhat.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Link: https://patch.msgid.link/20260112165352.138606-2-mlombard@redhat.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/target/iscsi/iscsi_target_util.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index 78aeaf67018f7..6998c0eec3d40 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -857,8 +857,11 @@ void iscsit_dec_conn_usage_count(struct iscsi_conn *conn)
 	spin_lock_bh(&conn->conn_usage_lock);
 	conn->conn_usage_count--;
 
-	if (!conn->conn_usage_count && conn->conn_waiting_on_uc)
+	if (!conn->conn_usage_count && conn->conn_waiting_on_uc) {
+		spin_unlock_bh(&conn->conn_usage_lock);
 		complete(&conn->conn_waiting_on_uc_comp);
+		return;
+	}
 
 	spin_unlock_bh(&conn->conn_usage_lock);
 }
-- 
2.51.0