From 1b4c59b7a1d0b9d8019254a5f2e35b2663f49a9e Mon Sep 17 00:00:00 2001
From: Hannes Reinecke <hare@suse.de>
Date: Mon, 22 Aug 2016 10:54:07 +0200
Subject: [PATCH] target: fix potential race window in
target_sess_cmd_list_waiting()
target_sess_cmd_list_waiting() might hit on a condition where
the kref for the command is already 0, but the destructor has
not been called yet (or is stuck in waiting for a spin lock).
Rather than leaving the command on the list we should explicitly
remove it to avoid race issues later on.
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
drivers/target/target_core_transport.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index e825d580ccee..7dfefd66df93 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2535,7 +2535,9 @@ int target_get_sess_cmd(struct se_cmd *se_cmd, bool ack_kref)
* invocations before se_cmd descriptor release.
*/
if (ack_kref) {
- kref_get(&se_cmd->cmd_kref);
+ if (!kref_get_unless_zero(&se_cmd->cmd_kref))
+ return -EINVAL;
+
se_cmd->se_cmd_flags |= SCF_ACK_KREF;
}
@@ -2616,7 +2618,7 @@ EXPORT_SYMBOL(target_put_sess_cmd);
*/
void target_sess_cmd_list_set_waiting(struct se_session *se_sess)
{
- struct se_cmd *se_cmd;
+ struct se_cmd *se_cmd, *tmp_cmd;
unsigned long flags;
int rc;
@@ -2628,14 +2630,16 @@ void target_sess_cmd_list_set_waiting(struct se_session *se_sess)
se_sess->sess_tearing_down = 1;
list_splice_init(&se_sess->sess_cmd_list, &se_sess->sess_wait_list);
- list_for_each_entry(se_cmd, &se_sess->sess_wait_list, se_cmd_list) {
+ list_for_each_entry_safe(se_cmd, tmp_cmd,
+ &se_sess->sess_wait_list, se_cmd_list) {
rc = kref_get_unless_zero(&se_cmd->cmd_kref);
if (rc) {
se_cmd->cmd_wait_set = 1;
spin_lock(&se_cmd->t_state_lock);
se_cmd->transport_state |= CMD_T_FABRIC_STOP;
spin_unlock(&se_cmd->t_state_lock);
- }
+ } else
+ list_del_init(&se_cmd->se_cmd_list);
}
spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
--
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