[IPV4/IPV6] multicast: Check add_grhead() return value

add_grhead() allocates memory with GFP_ATOMIC and in at least two places skb
from it passed to skb_put() without checking.

Signed-off-by: Alexey Dobriyan <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
2 files changed