[PATCH 4.4 03/73] scsi: vmw_pscsi: Fix use-after-free in pvscsi_queue_lck()

[Greg Kroah-Hartman]

From: Jan Kara <j...@suse.cz>

commit 240b4cc8fd5db138b675297d4226ec46594d9b3b upstream.

Once we unlock adapter->hw_lock in pvscsi_queue_lck() nothing prevents just
queued scsi_cmnd from completing and freeing the request. Thus cmd->cmnd[0]
dereference can dereference already freed request leading to kernel crashes
or other issues (which one of our customers observed). Store cmd->cmnd[0]
in a local variable before unlocking adapter->hw_lock to fix the issue.

CC: <sta...@vger.kernel.org>
Signed-off-by: Jan Kara <j...@suse.cz>
Reviewed-by: Ewan D. Milne <emi...@redhat.com>
Signed-off-by: Martin K. Petersen <martin.peter...@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/scsi/vmw_pvscsi.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/scsi/vmw_pvscsi.c
+++ b/drivers/scsi/vmw_pvscsi.c
@@ -733,6 +733,7 @@ static int pvscsi_queue_lck(struct scsi_
        struct pvscsi_adapter *adapter = shost_priv(host);
        struct pvscsi_ctx *ctx;
        unsigned long flags;
+       unsigned char op;
 
        spin_lock_irqsave(&adapter->hw_lock, flags);
 
@@ -745,13 +746,14 @@ static int pvscsi_queue_lck(struct scsi_
        }
 
        cmd->scsi_done = done;
+       op = cmd->cmnd[0];
 
        dev_dbg(&cmd->device->sdev_gendev,
-               "queued cmd %p, ctx %p, op=%x\n", cmd, ctx, cmd->cmnd[0]);
+               "queued cmd %p, ctx %p, op=%x\n", cmd, ctx, op);
 
        spin_unlock_irqrestore(&adapter->hw_lock, flags);
 
-       pvscsi_kick_io(adapter, cmd->cmnd[0]);
+       pvscsi_kick_io(adapter, op);
 
        return 0;
 }