usb: storage: return on error to avoid a null pointer dereference

commit 446230f52a5bef593554510302465eabab45a372 upstream.

When us->extra is null the driver is not initialized, however, a
later call to osd200_scsi_to_ata is made that dereferences
us->extra, causing a null pointer dereference.  The code
currently detects and reports that the driver is not initialized;
add a return to avoid the subsequent dereference issue in this
check.

Thanks to Alan Stern for pointing out that srb->result needs setting
to DID_ERROR << 16

Detected by CoverityScan, CID#100308 ("Dereference after null check")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/storage/isd200.c b/drivers/usb/storage/isd200.c
index ffc4193..36f18b5 100644 (file)
--- a/drivers/usb/storage/isd200.c
+++ b/drivers/usb/storage/isd200.c
@@ -1522,8 +1522,11 @@ static void isd200_ata_command(struct scsi_cmnd *srb, struct us_data *us)
 
        /* Make sure driver was initialized */
 
-       if (us->extra == NULL)
+       if (us->extra == NULL) {
                US_DEBUGP("ERROR Driver not initialized\n");
+               srb->result = DID_ERROR << 16;
+               return;
+       }
 
        scsi_set_resid(srb, 0);
        /* scsi_bufflen might change in protocol translation to ata */