[PATCH v2 0/3] scsi:iscsi: handle iscsi_cls_conn device with sysfs

[Wenchao Hao]

We found a NULL pointer dereference in iscsi_sw_tcp_conn_get_param(),
the root reason is we did sysfs addition wrong.

iscsi_create_conn() expose iscsi_cls_conn to sysfs while the related
resources are not initialized. So we should delay the calling of
device_add() until these resources has been initialized.

This patchset solve this issue by correct the add and teardown flow
of iscsi_cls_conn.

-----------
V2:
add two more iscsi_free_conn() and iscsi_remove_conn() than V1
change the teardown flow of iscsi_cls_conn

Wenchao Hao (3):
scsi: iscsi: Add helper functions to manage iscsi_cls_conn
scsi:libiscsi: Add iscsi_cls_conn to sysfs after been initialized
scsi:libiscsi: teardown iscsi_cls_conn gracefully

drivers/scsi/libiscsi.c | 21 ++++++---
drivers/scsi/scsi_transport_iscsi.c | 72 +++++++++++++++++++++--------
include/scsi/scsi_transport_iscsi.h | 5 +-
3 files changed, 71 insertions(+), 27 deletions(-)

--
2.32.0

[Wenchao Hao]

commit 1b8d0300a3e9 ("scsi: libiscsi: Fix UAF in
iscsi_conn_get_param()/iscsi_conn_teardown()") fixed an UAF in
iscsi_conn_get_param() and introduced 2 tmp_xxx varibles, the
implement looks ugly.

We can fix this UAF with the help of device_del() gracefully.
Call iscsi_remove_conn() at the beginning of iscsi_conn_teardown would
make userspace unable to see iscsi_cls_conn any more, then we can free
memory safely.

Signed-off-by: Wenchao Hao <haowe...@huawei.com>
Signed-off-by: Wu Bo <wub...@huawei.com>
---
drivers/scsi/libiscsi.c | 8 ++++----
drivers/scsi/scsi_transport_iscsi.c | 3 ++-
2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 43f903bce0b8..0d57521751dd 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3109,8 +3109,8 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
{
struct iscsi_conn *conn = cls_conn->dd_data;
struct iscsi_session *session = conn->session;
- char *tmp_persistent_address = conn->persistent_address;
- char *tmp_local_ipaddr = conn->local_ipaddr;
+
+ iscsi_remove_conn(cls_conn);

del_timer_sync(&conn->transport_timer);

@@ -3132,6 +3132,8 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
spin_lock_bh(&session->frwd_lock);
free_pages((unsigned long) conn->data,
get_order(ISCSI_DEF_MAX_RECV_SEG_LEN));
+ kfree(conn->persistent_address);
+ kfree(conn->local_ipaddr);
/* regular RX path uses back_lock */
spin_lock_bh(&session->back_lock);
kfifo_in(&session->cmdpool.queue, (void*)&conn->login_task,
@@ -3143,8 +3145,6 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
mutex_unlock(&session->eh_mutex);

iscsi_destroy_conn(cls_conn);
- kfree(tmp_persistent_address);
- kfree(tmp_local_ipaddr);
}
EXPORT_SYMBOL_GPL(iscsi_conn_teardown);

diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index ca724eed4f4d..7b4d998708e7 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -2165,6 +2165,7 @@ static int iscsi_iter_destroy_conn_fn(struct device *dev, void *data)
{
if (!iscsi_is_conn_dev(dev))
return 0;
+ iscsi_remove_conn(iscsi_dev_to_conn(dev));
return iscsi_destroy_conn(iscsi_dev_to_conn(dev));
}

@@ -2463,7 +2464,7 @@ int iscsi_destroy_conn(struct iscsi_cls_conn *conn)

transport_unregister_device(&conn->dev);
ISCSI_DBG_TRANS_CONN(conn, "Completing conn destruction\n");
- device_unregister(&conn->dev);
+ iscsi_free_conn(conn);
return 0;
}
EXPORT_SYMBOL_GPL(iscsi_destroy_conn);
--
2.32.0

[Wenchao Hao]

iscsi_create_conn() would expose iscsi_cls_conn to sysfs, while the
initialization of iscsi_conn's dd_data is not ready now. When userspace
try to access an attribute such as connect's address, it might cause
a NULL pointer dereference.

So we should add iscsi_cls_conn to sysfs until it has been initialized.

Remove iscsi_create_conn() by hand since it is not used now.

Signed-off-by: Wenchao Hao <haowe...@huawei.com>
Signed-off-by: Wu Bo <wub...@huawei.com>
---

drivers/scsi/libiscsi.c | 13 ++++-
drivers/scsi/scsi_transport_iscsi.c | 76 -----------------------------
include/scsi/scsi_transport_iscsi.h | 2 -
3 files changed, 11 insertions(+), 80 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 059dae8909ee..43f903bce0b8 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3040,8 +3040,9 @@ iscsi_conn_setup(struct iscsi_cls_session *cls_session, int dd_size,
struct iscsi_conn *conn;
struct iscsi_cls_conn *cls_conn;
char *data;
+ int err;

- cls_conn = iscsi_create_conn(cls_session, sizeof(*conn) + dd_size,
+ cls_conn = iscsi_alloc_conn(cls_session, sizeof(*conn) + dd_size,
conn_idx);
if (!cls_conn)
return NULL;
@@ -3078,13 +3079,21 @@ iscsi_conn_setup(struct iscsi_cls_session *cls_session, int dd_size,
goto login_task_data_alloc_fail;
conn->login_task->data = conn->data = data;

+ err = iscsi_add_conn(cls_conn);
+ if (err)
+ goto login_task_add_dev_fail;
+
return cls_conn;

+login_task_add_dev_fail:
+ free_pages((unsigned long) conn->data,
+ get_order(ISCSI_DEF_MAX_RECV_SEG_LEN));
+
login_task_data_alloc_fail:
kfifo_in(&session->cmdpool.queue, (void*)&conn->login_task,
sizeof(void*));
login_task_alloc_fail:
- iscsi_destroy_conn(cls_conn);
+ iscsi_free_conn(cls_conn);
return NULL;
}
EXPORT_SYMBOL_GPL(iscsi_conn_setup);
diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index 8e97c6f88359..ca724eed4f4d 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -2447,82 +2447,6 @@ void iscsi_free_conn(struct iscsi_cls_conn *conn)
}
EXPORT_SYMBOL_GPL(iscsi_free_conn);

-/**
- * iscsi_create_conn - create iscsi class connection
- * @session: iscsi cls session
- * @dd_size: private driver data size
- * @cid: connection id
- *
- * This can be called from a LLD or iscsi_transport. The connection
- * is child of the session so cid must be unique for all connections
- * on the session.
- *
- * Since we do not support MCS, cid will normally be zero. In some cases
- * for software iscsi we could be trying to preallocate a connection struct
- * in which case there could be two connection structs and cid would be
- * non-zero.
- */
-struct iscsi_cls_conn *
-iscsi_create_conn(struct iscsi_cls_session *session, int dd_size, uint32_t cid)
-{
- struct iscsi_transport *transport = session->transport;
- struct iscsi_cls_conn *conn;
- unsigned long flags;
- int err;
-
- conn = kzalloc(sizeof(*conn) + dd_size, GFP_KERNEL);
- if (!conn)
- return NULL;
- if (dd_size)
- conn->dd_data = &conn[1];
-
- mutex_init(&conn->ep_mutex);
- INIT_LIST_HEAD(&conn->conn_list);
- INIT_WORK(&conn->cleanup_work, iscsi_cleanup_conn_work_fn);
- conn->transport = transport;
- conn->cid = cid;
- conn->state = ISCSI_CONN_DOWN;
-
- /* this is released in the dev's release function */
- if (!get_device(&session->dev))
- goto free_conn;
-
- dev_set_name(&conn->dev, "connection%d:%u", session->sid, cid);
- conn->dev.parent = &session->dev;
- conn->dev.release = iscsi_conn_release;
- err = device_register(&conn->dev);
- if (err) {
- iscsi_cls_session_printk(KERN_ERR, session, "could not "
- "register connection's dev\n");
- goto release_parent_ref;
- }
- err = transport_register_device(&conn->dev);
- if (err) {
- iscsi_cls_session_printk(KERN_ERR, session, "could not "
- "register transport's dev\n");
- goto release_conn_ref;
- }
-
- spin_lock_irqsave(&connlock, flags);
- list_add(&conn->conn_list, &connlist);
- spin_unlock_irqrestore(&connlock, flags);
-
- ISCSI_DBG_TRANS_CONN(conn, "Completed conn creation\n");
- return conn;
-
-release_conn_ref:
- device_unregister(&conn->dev);
- put_device(&session->dev);
- return NULL;
-release_parent_ref:
- put_device(&session->dev);
-free_conn:
- kfree(conn);
- return NULL;
-}
-
-EXPORT_SYMBOL_GPL(iscsi_create_conn);
-
/**
* iscsi_destroy_conn - destroy iscsi class connection
* @conn: iscsi cls session
diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
index 346f65bc3861..505764942f5e 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -446,8 +446,6 @@ extern struct iscsi_cls_conn *iscsi_alloc_conn(struct iscsi_cls_session *sess,
extern int iscsi_add_conn(struct iscsi_cls_conn *conn);
extern void iscsi_remove_conn(struct iscsi_cls_conn *conn);
extern void iscsi_free_conn(struct iscsi_cls_conn *conn);
-extern struct iscsi_cls_conn *iscsi_create_conn(struct iscsi_cls_session *sess,
- int dd_size, uint32_t cid);
extern void iscsi_put_conn(struct iscsi_cls_conn *conn);
extern void iscsi_get_conn(struct iscsi_cls_conn *conn);
extern int iscsi_destroy_conn(struct iscsi_cls_conn *conn);
--
2.32.0

[Mike Christie]

On 3/8/22 9:09 PM, Wenchao Hao wrote:
> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> index ca724eed4f4d..7b4d998708e7 100644
> --- a/drivers/scsi/scsi_transport_iscsi.c
> +++ b/drivers/scsi/scsi_transport_iscsi.c
> @@ -2165,6 +2165,7 @@ static int iscsi_iter_destroy_conn_fn(struct device *dev, void *data)
> {
> if (!iscsi_is_conn_dev(dev))
> return 0;
> + iscsi_remove_conn(iscsi_dev_to_conn(dev));
> return iscsi_destroy_conn(iscsi_dev_to_conn(dev));

Just do:

iscsi_remove_conn
iscsi_put_conn
return 0;

[Mike Christie]

On 3/8/22 9:09 PM, Wenchao Hao wrote:

> @@ -3143,8 +3145,6 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
> mutex_unlock(&session->eh_mutex);
>
> iscsi_destroy_conn(cls_conn);

This should then be a iscsi_put_conn.

So basically it balances out.

iscsi_alloc_conn requires iscsi_put_conn. The put releases what is
done in the alloc. The put on the parent is done in the release though.

iscsi_add_conn requires iscsi_remove_conn. The remove undoes what
was done in the add

We don't want a iscsi_destroy_conn which does a iscsi_free_conn
because it makes it confusing.