[PATCH 4.9 048/102] scsi: vmw_pscsi: Fix use-after-free in pvscsi_queue_lck()

Greg Kroah-Hartman
2019-07-08T15:45:13Z

From: Jan Kara <jack@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: <stable@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@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
@@ -766,6 +766,7 @@ 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);

@@ -778,13 +779,14 @@ 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;
}