Syzbot reported a warning at `add_timer`, which is called from the
`atm_mpoa_mpoad_attach` function

The reason for this warning is that in the allocation failure by `alloc_mpc`,
there is lack of proper cleanup. And in the event that ATMMPC_CTRL ioctl is
called on to again, it will lead to the attempt of starting an already 
started timer from the previous ioctl call

Do a `timer_delete` before returning from the `alloc_mpc` failure

Reported-by: syzbot+07b635b9c111c566af8b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=07b635b9c111c566af8b
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Deepak Sharma <redacted>
---
 net/atm/mpc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/atm/mpc.c b/net/atm/mpc.c
index f6b447bba329..cd3295c3c480 100644
--- a/net/atm/mpc.c
+++ b/net/atm/mpc.c

@@ -814,7 +814,10 @@ static int atm_mpoa_mpoad_attach(struct atm_vcc *vcc, int arg)
 		dprintk("allocating new mpc for itf %d\n", arg);
 		mpc = alloc_mpc();
 		if (mpc == NULL)
+		{
+			timer_delete(&mpc_timer);
 			return -ENOMEM;
+		}
 		mpc->dev_num = arg;
 		mpc->dev = find_lec_by_itfnum(arg);
 					/* NULL if there was no lec */

-- 
2.51.0