[PATCH] ata: fix a race condition when internal cmd time out

[Jason Yan]

For internal cmds, we will unmap DMA memory associated with the cmd
before we abort the cmd. If DMA transfering data before the aborting,
bus error will occured.

ata_exec_internal_sg
  ->ata_port_freeze if timeout
    ->ata_qc_complete
      ->ata_sg_clean
                                      dma transfering data = bus error
  ->ap->ops->post_internal_cmd
    ->sas_ata_post_internal
      ->sas_ata_internal_abort
        ->abort the cmd

Fix this by move post_internal_cmd() before unmapping the DMA memory
when time out. Notice that we have to set ATA_QCFLAG_FAILED flag before
calling post_internal_cmd() so that the aborting will work.

Reported-by: luojian <luoji...@huawei.com>
Signed-off-by: Jason Yan <yanai...@huawei.com>
---
 drivers/ata/libata-core.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index adf28788cab5..d0ff5711e805 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1665,6 +1665,13 @@ unsigned ata_exec_internal_sg(struct ata_device *dev,
                 */
                if (qc->flags & ATA_QCFLAG_ACTIVE) {
                        qc->err_mask |= AC_ERR_TIMEOUT;
+                       qc->flags |= ATA_QCFLAG_FAILED;
+
+                       spin_unlock_irqrestore(ap->lock, flags);
+                       /* do post_internal_cmd */
+                       if (ap->ops->post_internal_cmd)
+                               ap->ops->post_internal_cmd(qc);
+                       spin_lock_irqsave(ap->lock, flags);
 
                        if (ap->ops->error_handler)
                                ata_port_freeze(ap);
@@ -1679,9 +1686,10 @@ unsigned ata_exec_internal_sg(struct ata_device *dev,
                spin_unlock_irqrestore(ap->lock, flags);
        }
 
-       /* do post_internal_cmd */
-       if (ap->ops->post_internal_cmd)
-               ap->ops->post_internal_cmd(qc);
+       if (!(qc->err_mask & AC_ERR_TIMEOUT))
+               /* do post_internal_cmd */
+               if (ap->ops->post_internal_cmd)
+                       ap->ops->post_internal_cmd(qc);
 
        /* perform minimal error analysis */
        if (qc->flags & ATA_QCFLAG_FAILED) {
-- 
2.14.4