Hi,
Please consider applying two patches in the attachment.
The problem (accessing session->conn_list after freeing session) was discovered using valgrind.
Note that while list_for_each_entry_safe is safe against current list element destruction,
it is UNSAFE against the traversed list_head (third argument) becoming invalid during iteration.
That's exactly what happens when the last connection of a session goes away (conn_exit -> session_put -> use-after-free).
--
Best regards,
Anton Kovalenko
From 16e64b10cbe829d0b0d06d22a54efd79b161427a Mon Sep 17 00:00:00 2001
From: Anton Kovalenko <anton.kovalenko@xxxxxxxxxxx>
Date: Wed, 3 May 2017 14:46:38 +0300
Subject: [PATCH 2/3] Avoid dangling session reference in login_security_done
---
usr/iscsi/iscsid.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/usr/iscsi/iscsid.c b/usr/iscsi/iscsid.c
index 700e2af..d5fe6b3 100644
--- a/usr/iscsi/iscsid.c
+++ b/usr/iscsi/iscsid.c
@@ -267,11 +267,12 @@ static void login_security_done(struct iscsi_connection *conn)
struct iscsi_connection *ent, *next;
/* do session reinstatement */
-
+ session_get(session);
list_for_each_entry_safe(ent, next, &session->conn_list,
clist) {
conn_close(ent);
}
+ session_put(session);
session = NULL;
} else if (req->tsih != session->tsih) {
--
2.11.0
From 67f7b51e6eddc55736a0bb85cbb3af95e73b68d6 Mon Sep 17 00:00:00 2001
From: Anton Kovalenko <anton.kovalenko@xxxxxxxxxxx>
Date: Wed, 3 May 2017 12:46:53 +0300
Subject: [PATCH 3/3] Avoid session* dangling reference on forced target
destroy.
Closing the last connection of a session also releases the session
itself, making session->conn_list inaccessible.
Wrapping conn_list iteration into session_get/session_put prevents
session destruction while its conn_list is being iterated.
---
usr/iscsi/target.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/usr/iscsi/target.c b/usr/iscsi/target.c
index bf54190..7d71206 100644
--- a/usr/iscsi/target.c
+++ b/usr/iscsi/target.c
@@ -411,9 +411,11 @@ void iscsi_target_destroy(int tid, int force)
}
list_for_each_entry_safe(session, stmp, &target->sessions_list, slist) {
+ session_get(session);
list_for_each_entry_safe(conn, ctmp, &session->conn_list, clist) {
conn_close(conn);
}
+ session_put(session);
}
if (!list_empty(&target->sessions_list)) {
--
2.11.0
