[PATCH 3.12 077/182] target/tcm_fc: Fix use-after-free of ft_tpg

Jiri Slaby
2014-05-13T09:56:28Z

From: Andy Grover <agrover@redhat.com>

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

===============

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@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/target/tcm_fc/tfc_sess.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/target/tcm_fc/tfc_sess.c b/drivers/target/tcm_fc/tfc_sess.c
index 4859505ae2ed..639fdb395fb7 100644
--- a/drivers/target/tcm_fc/tfc_sess.c
+++ b/drivers/target/tcm_fc/tfc_sess.c
@@ -68,6 +68,7 @@ static struct ft_tport *ft_tport_create(struct fc_lport *lport)

if (tport) {
tport->tpg = tpg;
+ tpg->tport = tport;
return tport;
}

--
1.9.3