target: close target_put_sess_cmd() vs. core_tmr_abort_task() race

It is possible for one thread to to take se_sess->sess_cmd_lock in
core_tmr_abort_task() before taking a reference count on
se_cmd->cmd_kref, while another thread in target_put_sess_cmd() drops
se_cmd->cmd_kref before taking se_sess->sess_cmd_lock.

This introduces kref_put_spinlock_irqsave() and uses it in
target_put_sess_cmd() to close the race window.

Signed-off-by: Joern Engel <joern@logfs.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 5 insertions, 6 deletions

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index c3477fa60942..4a793362309d 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2211,21 +2211,19 @@ static void target_release_cmd_kref(struct kref *kref)
 {
         struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
         struct se_session *se_sess = se_cmd->se_sess;
-        unsigned long flags;
 
-        spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
         if (list_empty(&se_cmd->se_cmd_list)) {
-                spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+                spin_unlock(&se_sess->sess_cmd_lock);
                 se_cmd->se_tfo->release_cmd(se_cmd);
                 return;
         }
         if (se_sess->sess_tearing_down && se_cmd->cmd_wait_set) {
-                spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+                spin_unlock(&se_sess->sess_cmd_lock);
                 complete(&se_cmd->cmd_wait_comp);
                 return;
         }
         list_del(&se_cmd->se_cmd_list);
-        spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+        spin_unlock(&se_sess->sess_cmd_lock);
 
         se_cmd->se_tfo->release_cmd(se_cmd);
 }
@@ -2236,7 +2234,8 @@ static void target_release_cmd_kref(struct kref *kref)
  */
 int target_put_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd)
 {
-        return kref_put(&se_cmd->cmd_kref, target_release_cmd_kref);
+        return kref_put_spinlock_irqsave(&se_cmd->cmd_kref, target_release_cmd_kref,
+                        &se_sess->sess_cmd_lock);
 }
 EXPORT_SYMBOL(target_put_sess_cmd);