[PATCH] uml: fix device unplug crash

Fix a NULL dereference when unplugging a device.  The default value of
err_msg wants to be "" in case the driver doesn't modify it.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 178b2eff4a8c..65ad2932672c 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -615,6 +615,9 @@ void mconsole_remove(struct mc_request *req)
         err_msg = NULL;
         err = (*dev->remove)(n, &err_msg);
         switch(err){
+        case 0:
+                err_msg = "";
+                break;
         case -ENODEV:
                 if(err_msg == NULL)
                         err_msg = "Device doesn't exist";