scsi: hisi_sas: fix the risk of freeing slot twice

BugLink: https://bugs.launchpad.net/bugs/1739807
The function hisi_sas_slot_task_free() is used to free the slot and do
tidy-up of LLDD resources. The LLDD generally should know the state of
a slot and decide when to free it, and it should only be done once.

For some scenarios, we really don't know the state, like when TMF
timeout. In this case, we check task->lldd_task before calling
hisi_sas_slot_task_free().

However, we may miss some scenarios when we should also check
task->lldd_task, and it is not SMP safe to check task->lldd_task as we
don't protect it within spin lock.

This patch is to fix this risk of freeing slot twice, as follows:

  1. Check task->lldd_task in the hisi_sas_slot_task_free(), and give
     up freeing of this time if task->lldd_task is NULL.

  2. Set slot->buf to NULL after it is freed.

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit 6ba0fbc35aa9f3bc8c12be3b4047055c9ce2ac92)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Paolo Pisati <paolo.pisati@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index 3afabd5f7f53c78c03a6965ab7941c9486ff7090..3ba65df1b1a11babf538e1bb5af3ba40c0220578 100644 (file)
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -176,13 +176,16 @@ void hisi_sas_slot_task_free(struct hisi_hba *hisi_hba, struct sas_task *task,
                struct domain_device *device = task->dev;
                struct hisi_sas_device *sas_dev = device->lldd_dev;
 
+               if (!task->lldd_task)
+                       return;
+
+               task->lldd_task = NULL;
+
                if (!sas_protocol_ata(task->task_proto))
                        if (slot->n_elem)
                                dma_unmap_sg(dev, task->scatter, slot->n_elem,
                                             task->data_dir);
 
-               task->lldd_task = NULL;
-
                if (sas_dev)
                        atomic64_dec(&sas_dev->running_req);
        }
@@ -190,8 +193,8 @@ void hisi_sas_slot_task_free(struct hisi_hba *hisi_hba, struct sas_task *task,
        if (slot->buf)
                dma_pool_free(hisi_hba->buffer_pool, slot->buf, slot->buf_dma);
 
-
        list_del_init(&slot->entry);
+       slot->buf = NULL;
        slot->task = NULL;
        slot->port = NULL;
        hisi_sas_slot_index_free(hisi_hba, slot->idx);