[PATCH 5.19 461/717] scsi: iscsi: iscsi_tcp: Fix null-ptr-deref while calling getpeername()

Greg Kroah-Hartman
2022-10-22T08:20:44Z

From: Mike Christie <michael.christie@oracle.com>

[ Upstream commit 57569c37f0add1b6489e1a1563c71519daf732cf ]

Fix a NULL pointer crash that occurs when we are freeing the socket at the
same time we access it via sysfs.

The problem is that:

1. iscsi_sw_tcp_conn_get_param() and iscsi_sw_tcp_host_get_param() take
the frwd_lock and do sock_hold() then drop the frwd_lock. sock_hold()
does a get on the "struct sock".

2. iscsi_sw_tcp_release_conn() does sockfd_put() which does the last put
on the "struct socket" and that does __sock_release() which sets the
sock->ops to NULL.

3. iscsi_sw_tcp_conn_get_param() and iscsi_sw_tcp_host_get_param() then
call kernel_getpeername() which accesses the NULL sock->ops.

Above we do a get on the "struct sock", but we needed a get on the "struct
socket". Originally, we just held the frwd_lock the entire time but in
commit bcf3a2953d36 ("scsi: iscsi: iscsi_tcp: Avoid holding spinlock while
calling getpeername()") we switched to refcount based because the network
layer changed and started taking a mutex in that path, so we could no
longer hold the frwd_lock.

Instead of trying to maintain multiple refcounts, this just has us use a
mutex for accessing the socket in the interface code paths.

Link: https://lore.kernel.org/r/20220907221700.10302-1-michael.christie@oracle.com
Fixes: bcf3a2953d36 ("scsi: iscsi: iscsi_tcp: Avoid holding spinlock while calling getpeername()")
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/iscsi_tcp.c | 73 ++++++++++++++++++++++++++++------------
drivers/scsi/iscsi_tcp.h | 3 ++
2 files changed, 55 insertions(+), 21 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 10d7f2b7dd0e..7e99070ea611 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -595,6 +595,8 @@ iscsi_sw_tcp_conn_create(struct iscsi_cls_session *cls_session,
INIT_WORK(&conn->recvwork, iscsi_sw_tcp_recv_data_work);
tcp_sw_conn->queue_recv = iscsi_recv_from_iscsi_q;

+ mutex_init(&tcp_sw_conn->sock_lock);
+
tfm = crypto_alloc_ahash("crc32c", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(tfm))
goto free_conn;
@@ -629,11 +631,15 @@ iscsi_sw_tcp_conn_create(struct iscsi_cls_session *cls_session,

static void iscsi_sw_tcp_release_conn(struct iscsi_conn *conn)
{
- struct iscsi_session *session = conn->session;
struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
struct socket *sock = tcp_sw_conn->sock;

+ /*
+ * The iscsi transport class will make sure we are not called in
+ * parallel with start, stop, bind and destroys. However, this can be
+ * called twice if userspace does a stop then a destroy.
+ */
if (!sock)
return;

@@ -649,9 +655,9 @@ static void iscsi_sw_tcp_release_conn(struct iscsi_conn *conn)

iscsi_suspend_rx(conn);

- spin_lock_bh(&session->frwd_lock);
+ mutex_lock(&tcp_sw_conn->sock_lock);
tcp_sw_conn->sock = NULL;
- spin_unlock_bh(&session->frwd_lock);
+ mutex_unlock(&tcp_sw_conn->sock_lock);
sockfd_put(sock);
}

@@ -703,7 +709,6 @@ iscsi_sw_tcp_conn_bind(struct iscsi_cls_session *cls_session,
struct iscsi_cls_conn *cls_conn, uint64_t transport_eph,
int is_leading)
{
- struct iscsi_session *session = cls_session->dd_data;
struct iscsi_conn *conn = cls_conn->dd_data;
struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
@@ -723,10 +728,10 @@ iscsi_sw_tcp_conn_bind(struct iscsi_cls_session *cls_session,
if (err)
goto free_socket;

- spin_lock_bh(&session->frwd_lock);
+ mutex_lock(&tcp_sw_conn->sock_lock);
/* bind iSCSI connection and socket */
tcp_sw_conn->sock = sock;
- spin_unlock_bh(&session->frwd_lock);
+ mutex_unlock(&tcp_sw_conn->sock_lock);

/* setup Socket parameters */
sk = sock->sk;
@@ -763,8 +768,15 @@ static int iscsi_sw_tcp_conn_set_param(struct iscsi_cls_conn *cls_conn,
break;
case ISCSI_PARAM_DATADGST_EN:
iscsi_set_param(cls_conn, param, buf, buflen);
+
+ mutex_lock(&tcp_sw_conn->sock_lock);
+ if (!tcp_sw_conn->sock) {
+ mutex_unlock(&tcp_sw_conn->sock_lock);
+ return -ENOTCONN;
+ }
tcp_sw_conn->sendpage = conn->datadgst_en ?
sock_no_sendpage : tcp_sw_conn->sock->ops->sendpage;
+ mutex_unlock(&tcp_sw_conn->sock_lock);
break;
case ISCSI_PARAM_MAX_R2T:
return iscsi_tcp_set_max_r2t(conn, buf);
@@ -779,8 +791,8 @@ static int iscsi_sw_tcp_conn_get_param(struct iscsi_cls_conn *cls_conn,
enum iscsi_param param, char *buf)
{
struct iscsi_conn *conn = cls_conn->dd_data;
- struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
- struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
+ struct iscsi_sw_tcp_conn *tcp_sw_conn;
+ struct iscsi_tcp_conn *tcp_conn;
struct sockaddr_in6 addr;
struct socket *sock;
int rc;
@@ -790,21 +802,36 @@ static int iscsi_sw_tcp_conn_get_param(struct iscsi_cls_conn *cls_conn,
case ISCSI_PARAM_CONN_ADDRESS:
case ISCSI_PARAM_LOCAL_PORT:
spin_lock_bh(&conn->session->frwd_lock);
- if (!tcp_sw_conn || !tcp_sw_conn->sock) {
+ if (!conn->session->leadconn) {
spin_unlock_bh(&conn->session->frwd_lock);
return -ENOTCONN;
}
- sock = tcp_sw_conn->sock;
- sock_hold(sock->sk);
+ /*
+ * The conn has been setup and bound, so just grab a ref
+ * incase a destroy runs while we are in the net layer.
+ */
+ iscsi_get_conn(conn->cls_conn);
spin_unlock_bh(&conn->session->frwd_lock);

+ tcp_conn = conn->dd_data;
+ tcp_sw_conn = tcp_conn->dd_data;
+
+ mutex_lock(&tcp_sw_conn->sock_lock);
+ sock = tcp_sw_conn->sock;
+ if (!sock) {
+ rc = -ENOTCONN;
+ goto sock_unlock;
+ }
+
if (param == ISCSI_PARAM_LOCAL_PORT)
rc = kernel_getsockname(sock,
(struct sockaddr *)&addr);
else
rc = kernel_getpeername(sock,
(struct sockaddr *)&addr);
- sock_put(sock->sk);
+sock_unlock:
+ mutex_unlock(&tcp_sw_conn->sock_lock);
+ iscsi_put_conn(conn->cls_conn);
if (rc < 0)
return rc;

@@ -842,17 +869,21 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
}
tcp_conn = conn->dd_data;
tcp_sw_conn = tcp_conn->dd_data;
- sock = tcp_sw_conn->sock;
- if (!sock) {
- spin_unlock_bh(&session->frwd_lock);
- return -ENOTCONN;
- }
- sock_hold(sock->sk);
+ /*
+ * The conn has been setup and bound, so just grab a ref
+ * incase a destroy runs while we are in the net layer.
+ */
+ iscsi_get_conn(conn->cls_conn);
spin_unlock_bh(&session->frwd_lock);

- rc = kernel_getsockname(sock,
- (struct sockaddr *)&addr);
- sock_put(sock->sk);
+ mutex_lock(&tcp_sw_conn->sock_lock);
+ sock = tcp_sw_conn->sock;
+ if (!sock)
+ rc = -ENOTCONN;
+ else
+ rc = kernel_getsockname(sock, (struct sockaddr *)&addr);
+ mutex_unlock(&tcp_sw_conn->sock_lock);
+ iscsi_put_conn(conn->cls_conn);
if (rc < 0)
return rc;

diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index 850a018aefb9..68e14a344904 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -28,6 +28,9 @@ struct iscsi_sw_tcp_send {

struct iscsi_sw_tcp_conn {
struct socket *sock;
+ /* Taken when accessing the sock from the netlink/sysfs interface */
+ struct mutex sock_lock;
+
struct work_struct recvwork;
bool queue_recv;

--
2.35.1