tcm_fc: Fix free-after-use regression in ft_free_cmd

commit ed8ec8f707ed4760c124d47b27c93df8ec5b1eba upstream.

This patch fixes a free-after-use regression in ft_free_cmd(), where
ft_sess_put() is called with cmd->sess after percpu_ida_free() has
already released the tag.

Fix this bug by saving the ft_sess pointer ahead of percpu_ida_free(),
and pass it directly to ft_sess_put().

The regression was originally introduced in v3.13-rc1 commit:

  commit 5f544cfac956971099e906f94568bc3fd1a7108a
  Author: Nicholas Bellinger <nab@daterainc.com>
  Date:   Mon Sep 23 12:12:42 2013 -0700

      tcm_fc: Convert to per-cpu command map pre-allocation of ft_cmd

Reported-by: Jun Wu <jwu@stormojo.com>
Cc: Mark Rustad <mark.d.rustad@intel.com>
Cc: Robert Love <robert.w.love@intel.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/target/tcm_fc/tfc_cmd.c b/drivers/target/tcm_fc/tfc_cmd.c
index 8b2c1aa..d22cdc7 100644 (file)
--- a/drivers/target/tcm_fc/tfc_cmd.c
+++ b/drivers/target/tcm_fc/tfc_cmd.c
@@ -90,18 +90,18 @@ static void ft_free_cmd(struct ft_cmd *cmd)
 {
        struct fc_frame *fp;
        struct fc_lport *lport;
-       struct se_session *se_sess;
+       struct ft_sess *sess;
 
        if (!cmd)
                return;
-       se_sess = cmd->sess->se_sess;
+       sess = cmd->sess;
        fp = cmd->req_frame;
        lport = fr_dev(fp);
        if (fr_seq(fp))
                lport->tt.seq_release(fr_seq(fp));
        fc_frame_free(fp);
-       percpu_ida_free(&se_sess->sess_tag_pool, cmd->se_cmd.map_tag);
-       ft_sess_put(cmd->sess); /* undo get from lookup at recv */
+       percpu_ida_free(&sess->se_sess->sess_tag_pool, cmd->se_cmd.map_tag);
+       ft_sess_put(sess);      /* undo get from lookup at recv */
 }
 
 void ft_release_cmd(struct se_cmd *se_cmd)