From: Mike Christie michael.christie@oracle.com
[ Upstream commit 7c6e99c18167ed89729bf167ccb4a7e3ab3115ba ]
If iscsid is doing a stop_conn at the same time the kernel is starting error recovery we can hit a race that allows the cleanup work to run on a valid connection. In the race, iscsi_if_stop_conn sees the cleanup bit set, but it calls flush_work on the clean_work before iscsi_conn_error_event has queued it. The flush then returns before the queueing and so the cleanup_work can run later and disconnect/stop a conn while it's in a connected state.
The patch:
Commit 0ab710458da1 ("scsi: iscsi: Perform connection failure entirely in kernel space")
added the late stop_conn call bug originally, and the patch:
Commit 23d6fefbb3f6 ("scsi: iscsi: Fix in-kernel conn failure handling")
attempted to fix it but only fixed the normal EH case and left the above race for the iscsid restart case. For the normal EH case we don't hit the race because we only signal userspace to start recovery after we have done the queueing, so the flush will always catch the queued work or see it completed.
For iscsid restart cases like boot, we can hit the race because iscsid will call down to the kernel before the kernel has signaled any error, so both code paths can be running at the same time. This adds a lock around the setting of the cleanup bit and queueing so they happen together.
Link: https://lore.kernel.org/r/20220408001314.5014-6-michael.christie@oracle.com Fixes: 0ab710458da1 ("scsi: iscsi: Perform connection failure entirely in kernel space") Tested-by: Manish Rangankar mrangankar@marvell.com Reviewed-by: Lee Duncan lduncan@suse.com Reviewed-by: Chris Leech cleech@redhat.com 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/scsi_transport_iscsi.c | 17 +++++++++++++++++ include/scsi/scsi_transport_iscsi.h | 2 ++ 2 files changed, 19 insertions(+)
diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c index 4fa2fd7f4c72..ed289e1242c9 100644 --- a/drivers/scsi/scsi_transport_iscsi.c +++ b/drivers/scsi/scsi_transport_iscsi.c @@ -2260,9 +2260,12 @@ static void iscsi_if_disconnect_bound_ep(struct iscsi_cls_conn *conn, bool is_active) { /* Check if this was a conn error and the kernel took ownership */ + spin_lock_irq(&conn->lock); if (!test_bit(ISCSI_CLS_CONN_BIT_CLEANUP, &conn->flags)) { + spin_unlock_irq(&conn->lock); iscsi_ep_disconnect(conn, is_active); } else { + spin_unlock_irq(&conn->lock); ISCSI_DBG_TRANS_CONN(conn, "flush kernel conn cleanup.\n"); mutex_unlock(&conn->ep_mutex);
@@ -2309,9 +2312,12 @@ static int iscsi_if_stop_conn(struct iscsi_transport *transport, /* * Figure out if it was the kernel or userspace initiating this. */ + spin_lock_irq(&conn->lock); if (!test_and_set_bit(ISCSI_CLS_CONN_BIT_CLEANUP, &conn->flags)) { + spin_unlock_irq(&conn->lock); iscsi_stop_conn(conn, flag); } else { + spin_unlock_irq(&conn->lock); ISCSI_DBG_TRANS_CONN(conn, "flush kernel conn cleanup.\n"); flush_work(&conn->cleanup_work); @@ -2320,7 +2326,9 @@ static int iscsi_if_stop_conn(struct iscsi_transport *transport, * Only clear for recovery to avoid extra cleanup runs during * termination. */ + spin_lock_irq(&conn->lock); clear_bit(ISCSI_CLS_CONN_BIT_CLEANUP, &conn->flags); + spin_unlock_irq(&conn->lock); } ISCSI_DBG_TRANS_CONN(conn, "iscsi if conn stop done.\n"); return 0; @@ -2341,7 +2349,9 @@ static void iscsi_cleanup_conn_work_fn(struct work_struct *work) */ if (conn->state != ISCSI_CONN_BOUND && conn->state != ISCSI_CONN_UP) { ISCSI_DBG_TRANS_CONN(conn, "Got error while conn is already failed. Ignoring.\n"); + spin_lock_irq(&conn->lock); clear_bit(ISCSI_CLS_CONN_BIT_CLEANUP, &conn->flags); + spin_unlock_irq(&conn->lock); mutex_unlock(&conn->ep_mutex); return; } @@ -2407,6 +2417,7 @@ iscsi_create_conn(struct iscsi_cls_session *session, int dd_size, uint32_t cid) conn->dd_data = &conn[1];
mutex_init(&conn->ep_mutex); + spin_lock_init(&conn->lock); INIT_LIST_HEAD(&conn->conn_list); INIT_WORK(&conn->cleanup_work, iscsi_cleanup_conn_work_fn); conn->transport = transport; @@ -2598,9 +2609,12 @@ void iscsi_conn_error_event(struct iscsi_cls_conn *conn, enum iscsi_err error) struct iscsi_uevent *ev; struct iscsi_internal *priv; int len = nlmsg_total_size(sizeof(*ev)); + unsigned long flags;
+ spin_lock_irqsave(&conn->lock, flags); if (!test_and_set_bit(ISCSI_CLS_CONN_BIT_CLEANUP, &conn->flags)) queue_work(iscsi_conn_cleanup_workq, &conn->cleanup_work); + spin_unlock_irqrestore(&conn->lock, flags);
priv = iscsi_if_transport_lookup(conn->transport); if (!priv) @@ -3743,11 +3757,14 @@ static int iscsi_if_transport_conn(struct iscsi_transport *transport, return -EINVAL;
mutex_lock(&conn->ep_mutex); + spin_lock_irq(&conn->lock); if (test_bit(ISCSI_CLS_CONN_BIT_CLEANUP, &conn->flags)) { + spin_unlock_irq(&conn->lock); mutex_unlock(&conn->ep_mutex); ev->r.retcode = -ENOTCONN; return 0; } + spin_unlock_irq(&conn->lock);
switch (nlh->nlmsg_type) { case ISCSI_UEVENT_BIND_CONN: diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h index c5d7810fd792..037c77fb5dc5 100644 --- a/include/scsi/scsi_transport_iscsi.h +++ b/include/scsi/scsi_transport_iscsi.h @@ -211,6 +211,8 @@ struct iscsi_cls_conn { struct mutex ep_mutex; struct iscsi_endpoint *ep;
+ /* Used when accessing flags and queueing work. */ + spinlock_t lock; unsigned long flags; struct work_struct cleanup_work;