uml: network interface hotplug error handling

This fixes a number of problems associated with network interface hotplug.

The userspace initialization function can fail in some cases, but the
failure was never passed back to eth_configure, which proceeded with the
configuration.  This results in a zombie device that is present, but can't
work.  This is fixed by allowing the initialization routines to return an
error, which is checked, and the configuration aborted on failure.

eth_configure failed to check for many failures.  Even when it did check,
it didn't undo whatever initializations has already happened, so a present,
but partially initialized and non-working device could result.  It now
checks everything that can fail, and bails out, undoing whatever had been
done.

The return value of eth_configure was always ignored, so it is now just
void.

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

2 files changed, 4 insertions, 2 deletions

diff --git a/arch/um/os-Linux/drivers/ethertap_user.c b/arch/um/os-Linux/drivers/ethertap_user.c
index f3ad0dac7cdc..2cc2d3ea2e6d 100644
--- a/arch/um/os-Linux/drivers/ethertap_user.c
+++ b/arch/um/os-Linux/drivers/ethertap_user.c
@@ -24,11 +24,12 @@
 
 #define MAX_PACKET ETH_MAX_PACKET
 
-void etap_user_init(void *data, void *dev)
+static int etap_user_init(void *data, void *dev)
 {
         struct ethertap_data *pri = data;
 
         pri->dev = dev;
+        return 0;
 }
 
 struct addr_change {
diff --git a/arch/um/os-Linux/drivers/tuntap_user.c b/arch/um/os-Linux/drivers/tuntap_user.c
index ab63fb6f9992..506ef09d83a0 100644
--- a/arch/um/os-Linux/drivers/tuntap_user.c
+++ b/arch/um/os-Linux/drivers/tuntap_user.c
@@ -24,11 +24,12 @@
 
 #define MAX_PACKET ETH_MAX_PACKET
 
-void tuntap_user_init(void *data, void *dev)
+static int tuntap_user_init(void *data, void *dev)
 {
         struct tuntap_data *pri = data;
 
         pri->dev = dev;
+        return 0;
 }
 
 static void tuntap_add_addr(unsigned char *addr, unsigned char *netmask,