[PATCH] scsi: vmw_pscsi: Fix use-after-free in pvscsi_queue_lck()

[Jan Kara]

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

diff --git a/drivers/scsi/vmw_pvscsi.c b/drivers/scsi/vmw_pvscsi.c
index ecee4b3ff073..377b07b2feeb 100644
--- a/drivers/scsi/vmw_pvscsi.c
+++ b/drivers/scsi/vmw_pvscsi.c
@@ -763,6 +763,7 @@ static int pvscsi_queue_lck(struct scsi_cmnd *cmd, void 
(*done)(struct scsi_cmnd
        struct pvscsi_adapter *adapter = shost_priv(host);
        struct pvscsi_ctx *ctx;
        unsigned long flags;
+       unsigned char op;
 
        spin_lock_irqsave(&adapter->hw_lock, flags);
 
@@ -775,13 +776,14 @@ static int pvscsi_queue_lck(struct scsi_cmnd *cmd, void 
(*done)(struct scsi_cmnd
        }
 
        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;
 }
-- 
2.16.4