firewire: fw-sbp2: fix NULL pointer deref. in slave_alloc

Fix a kernel bug when running rescan-scsi-bus while a FireWire disk is
connected:  http://bugzilla.kernel.org/show_bug.cgi?id=10008

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
index ea4811c45512..60ebcb5fe21a 100644
--- a/drivers/firewire/fw-sbp2.c
+++ b/drivers/firewire/fw-sbp2.c
@@ -1473,6 +1473,10 @@ static int sbp2_scsi_slave_alloc(struct scsi_device *sdev)
 {
         struct sbp2_logical_unit *lu = sdev->hostdata;
 
+        /* (Re-)Adding logical units via the SCSI stack is not supported. */
+        if (!lu)
+                return -ENOSYS;
+
         sdev->allow_restart = 1;
 
         /*