From 5319d0b176ecb5b225f14cc64da196542679bf07 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Wed, 22 Jul 2015 00:24:09 -0700 Subject: [PATCH] iscsi-target: Fix use-after-free during TPG session shutdown 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 Cc: Sunilkumar Nadumuttlu Signed-off-by: Nicholas Bellinger Signed-off-by: Greg Kroah-Hartman --- drivers/target/iscsi/iscsi_target.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c index 3c293ad6ae7..e91266974c0 100644 --- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -4649,6 +4649,7 @@ int iscsit_release_sessions_for_tpg(struct iscsi_portal_group *tpg, int force) 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(struct iscsi_portal_group *tpg, int force) } 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); -- 2.20.1