linux-kernel - [PATCH 3.2 87/94] target/tcm_fc: Fix use-after-free of ft

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Date:	Mon, 28 Apr 2014 02:11:22 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Nicholas Bellinger" <nab@...ux-iscsi.org>,
	"Andy Grover" <agrover@...hat.com>
Subject: [PATCH 3.2 87/94] target/tcm_fc: Fix use-after-free of ft_tpg

3.2.58-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Andy Grover <agrover@...hat.com>

commit 2c42be2dd4f6586728dba5c4e197afd5cfaded78 upstream.

ft_del_tpg checks tpg->tport is set before unlinking the tpg from the
tport when the tpg is being removed. Set this pointer in ft_tport_create,
or the unlinking won't happen in ft_del_tpg and tport->tpg will reference
a deleted object.

This patch sets tpg->tport in ft_tport_create, because that's what
ft_del_tpg checks, and is the only way to get back to the tport to
clear tport->tpg.

The bug was occuring when:

- lport created, tport (our per-lport, per-provider context) is
  allocated.
  tport->tpg = NULL
- tpg created
- a PRLI is received. ft_tport_create is called, tpg is found and
  tport->tpg is set
- tpg removed. ft_tpg is freed in ft_del_tpg. Since tpg->tport was not
  set, tport->tpg is not cleared and points at freed memory
- Future calls to ft_tport_create return tport via first conditional,
  instead of searching for new tpg by calling ft_lport_find_tpg.
  tport->tpg is still invalid, and will access freed memory.

see https://bugzilla.redhat.com/show_bug.cgi?id=1071340

Signed-off-by: Andy Grover <agrover@...hat.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/target/tcm_fc/tfc_sess.c | 1 +
 1 file changed, 1 insertion(+)

--- a/drivers/target/tcm_fc/tfc_sess.c
+++ b/drivers/target/tcm_fc/tfc_sess.c
@@ -72,6 +72,7 @@ static struct ft_tport *ft_tport_create(
 
 	if (tport) {
 		tport->tpg = tpg;
+		tpg->tport = tport;
 		return tport;
 	}
 

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