linux-kernel - [PATCH 3.13 132/212] tcm_fc: Fix free-after-use regression in ft_free

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Date:	Tue, 17 Jun 2014 14:43:46 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Mark Rustad <mark.d.rustad@...el.com>,
	Robert Love <robert.w.love@...el.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 132/212] tcm_fc: Fix free-after-use regression in ft_free_cmd

3.13.11.4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab@...ux-iscsi.org>

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@...erainc.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@...rmojo.com>
Cc: Mark Rustad <mark.d.rustad@...el.com>
Cc: Robert Love <robert.w.love@...el.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/target/tcm_fc/tfc_cmd.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/target/tcm_fc/tfc_cmd.c b/drivers/target/tcm_fc/tfc_cmd.c
index 8b2c1aa..d22cdc7 100644
--- 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)
-- 
1.9.1

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