crypto: skcipher - avoid NULL dereference

Stanse found a potential NULL dereference in ablkcipher_next_slow.
Even though kmalloc fails, its retval is dereferenced later. Return
from that function properly earlier.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

crypto/ablkcipher.c

@@ -165,7 +165,7 @@ static inline int ablkcipher_next_slow(struct ablkcipher_request *req,
 
 	p = kmalloc(n, GFP_ATOMIC);
 	if (!p)
-		ablkcipher_walk_done(req, walk, -ENOMEM);
+		return ablkcipher_walk_done(req, walk, -ENOMEM);
 
 	base = p + 1;