| From 417c20a9bdd1e876384127cf096d8ae8b559066c Mon Sep 17 00:00:00 2001 |
| From: Nicholas Bellinger <nab@linux-iscsi.org> |
| Date: Wed, 22 Jul 2015 00:24:09 -0700 |
| Subject: iscsi-target: Fix use-after-free during TPG session shutdown |
| |
| From: Nicholas Bellinger <nab@linux-iscsi.org> |
| |
| commit 417c20a9bdd1e876384127cf096d8ae8b559066c upstream. |
| |
| This patch fixes a use-after-free bug in iscsit_release_sessions_for_tpg() |
| where se_portal_group->session_lock was incorrectly released/re-acquired |
| while walking the active se_portal_group->tpg_sess_list. |
| |
| The can result in a NULL pointer dereference when iscsit_close_session() |
| shutdown happens in the normal path asynchronously to this code, causing |
| a bogus dereference of an already freed list entry to occur. |
| |
| To address this bug, walk the session list checking for the same state |
| as before, but move entries to a local list to avoid dropping the lock |
| while walking the active list. |
| |
| As before, signal using iscsi_session->session_restatement=1 for those |
| list entries to be released locally by iscsit_free_session() code. |
| |
| Reported-by: Sunilkumar Nadumuttlu <sjn@datera.io> |
| Cc: Sunilkumar Nadumuttlu <sjn@datera.io> |
| Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/target/iscsi/iscsi_target.c | 12 ++++++++---- |
| 1 file changed, 8 insertions(+), 4 deletions(-) |
| |
| --- a/drivers/target/iscsi/iscsi_target.c |
| +++ b/drivers/target/iscsi/iscsi_target.c |
| @@ -4649,6 +4649,7 @@ int iscsit_release_sessions_for_tpg(stru |
| struct iscsi_session *sess; |
| struct se_portal_group *se_tpg = &tpg->tpg_se_tpg; |
| struct se_session *se_sess, *se_sess_tmp; |
| + LIST_HEAD(free_list); |
| int session_count = 0; |
| |
| spin_lock_bh(&se_tpg->session_lock); |
| @@ -4670,14 +4671,17 @@ int iscsit_release_sessions_for_tpg(stru |
| } |
| atomic_set(&sess->session_reinstatement, 1); |
| spin_unlock(&sess->conn_lock); |
| - spin_unlock_bh(&se_tpg->session_lock); |
| |
| - iscsit_free_session(sess); |
| - spin_lock_bh(&se_tpg->session_lock); |
| + list_move_tail(&se_sess->sess_list, &free_list); |
| + } |
| + spin_unlock_bh(&se_tpg->session_lock); |
| |
| + list_for_each_entry_safe(se_sess, se_sess_tmp, &free_list, sess_list) { |
| + sess = (struct iscsi_session *)se_sess->fabric_sess_ptr; |
| + |
| + iscsit_free_session(sess); |
| session_count++; |
| } |
| - spin_unlock_bh(&se_tpg->session_lock); |
| |
| pr_debug("Released %d iSCSI Session(s) from Target Portal" |
| " Group: %hu\n", session_count, tpg->tpgt); |