treewide: use get_random_{u8,u16}() when possible, part 1

Rather than truncate a 32-bit value to a 16-bit value or an 8-bit value,
simply use the get_random_{u8,u16}() functions, which are faster than
wasting the additional bytes from a 32-bit value. This was done
mechanically with this coccinelle script:

@@
expression E;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u16;
typedef __be16;
typedef __le16;
typedef u8;
@@
(
- (get_random_u32() & 0xffff)
+ get_random_u16()
|
- (get_random_u32() & 0xff)
+ get_random_u8()
|
- (get_random_u32() % 65536)
+ get_random_u16()
|
- (get_random_u32() % 256)
+ get_random_u8()
|
- (get_random_u32() >> 16)
+ get_random_u16()
|
- (get_random_u32() >> 24)
+ get_random_u8()
|
- (u16)get_random_u32()
+ get_random_u16()
|
- (u8)get_random_u32()
+ get_random_u8()
|
- (__be16)get_random_u32()
+ (__be16)get_random_u16()
|
- (__le16)get_random_u32()
+ (__le16)get_random_u16()
|
- prandom_u32_max(65536)
+ get_random_u16()
|
- prandom_u32_max(256)
+ get_random_u8()
|
- E->inet_id = get_random_u32()
+ E->inet_id = get_random_u16()
)

@@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u16;
identifier v;
@@
- u16 v = get_random_u32();
+ u16 v = get_random_u16();

@@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u8;
identifier v;
@@
- u8 v = get_random_u32();
+ u8 v = get_random_u8();

@@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u16;
u16 v;
@@
- v = get_random_u32();
+ v = get_random_u16();

@@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u8;
u8 v;
@@
- v = get_random_u32();
+ v = get_random_u8();

// Find a potential literal
@literal_mask@
expression LITERAL;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
position p;
@@

((T)get_random_u32()@p & (LITERAL))

// Examine limits
@script:python add_one@
literal << literal_mask.LITERAL;
RESULT;
@@

value = None
if literal.startswith('0x'):
value = int(literal, 16)
elif literal[0] in '123456789':
value = int(literal, 10)
if value is None:
print("I don't know how to handle %s" % (literal))
cocci.include_match(False)
elif value < 256:
coccinelle.RESULT = cocci.make_ident("get_random_u8")
elif value < 65536:
coccinelle.RESULT = cocci.make_ident("get_random_u16")
else:
print("Skipping large mask of %s" % (literal))
cocci.include_match(False)

// Replace the literal mask with the calculated result.
@plus_one@
expression literal_mask.LITERAL;
position literal_mask.p;
identifier add_one.RESULT;
identifier FUNC;
@@

- (FUNC()@p & (LITERAL))
+ (RESULT() & LITERAL)

Reviewed-by: Greg Kroah-Hartman <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Reviewed-by: Yury Norov <[e-mail]>
Acked-by: Jakub Kicinski <[e-mail]>
Acked-by: Toke Høiland-Jørgensen <[e-mail]> # for sch_cake
Signed-off-by: Jason A. Donenfeld <[e-mail]>

arch/arm/kernel/signal.c

···
 		 PAGE_SIZE / sizeof(u32));
 
 	/* Give the signal return code some randomness */
-	offset = 0x200 + (get_random_int() & 0x7fc);
+	offset = 0x200 + (get_random_u16() & 0x7fc);
 	signal_return_offset = offset;
 
 	/* Copy signal return handlers into the page */

arch/arm64/kernel/syscall.c

···
 	 *
 	 * The resulting 5 bits of entropy is seen in SP[8:4].
 	 */
-	choose_random_kstack_offset(get_random_int() & 0x1FF);
+	choose_random_kstack_offset(get_random_u16() & 0x1FF);
 }
 
 static inline bool has_syscall_work(unsigned long flags)

crypto/testmgr.c

···
 			b = 0xff;
 			break;
 		default:
-			b = (u8)prandom_u32();
+			b = get_random_u8();
 			break;
 		}
 		memset(buf, b, count);
···
 		break;
 	case 2:
 		/* Ascending or descending bytes, plus optional mutations */
-		increment = (u8)prandom_u32();
-		b = (u8)prandom_u32();
+		increment = get_random_u8();
+		b = get_random_u8();
 		for (i = 0; i < count; i++, b += increment)
 			buf[i] = b;
 		mutate_buffer(buf, count);
···
 	default:
 		/* Fully random bytes */
 		for (i = 0; i < count; i++)
-			buf[i] = (u8)prandom_u32();
+			buf[i] = get_random_u8();
 	}
 }
 

drivers/media/common/v4l2-tpg/v4l2-tpg-core.c

···
 		g = tpg_colors[col].g;
 		b = tpg_colors[col].b;
 	} else if (tpg->pattern == TPG_PAT_NOISE) {
-		r = g = b = prandom_u32_max(256);
+		r = g = b = get_random_u8();
 	} else if (k == TPG_COLOR_RANDOM) {
 		r = g = b = tpg->qual_offset + prandom_u32_max(196);
 	} else if (k >= TPG_COLOR_RAMP) {

drivers/media/test-drivers/vivid/vivid-radio-rx.c

···
 				break;
 			case 2:
 				rds.block |= V4L2_RDS_BLOCK_ERROR;
-				rds.lsb = prandom_u32_max(256);
-				rds.msb = prandom_u32_max(256);
+				rds.lsb = get_random_u8();
+				rds.msb = get_random_u8();
 				break;
 			case 3: /* Skip block altogether */
 				if (i)

drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c

···
 	tp->write_seq = snd_isn;
 	tp->snd_nxt = snd_isn;
 	tp->snd_una = snd_isn;
-	inet_sk(sk)->inet_id = prandom_u32();
+	inet_sk(sk)->inet_id = get_random_u16();
 	assign_rxopt(sk, opt);
 
 	if (tp->rcv_wnd > (RCV_BUFSIZ_M << 10))

drivers/net/hamradio/baycom_epp.c

···
 			if ((--bc->hdlctx.slotcnt) > 0)
 				return 0;
 			bc->hdlctx.slotcnt = bc->ch_params.slottime;
-			if (prandom_u32_max(256) > bc->ch_params.ppersist)
+			if (get_random_u8() > bc->ch_params.ppersist)
 				return 0;
 		}
 	}

drivers/net/hamradio/hdlcdrv.c

···
 	if ((--s->hdlctx.slotcnt) > 0)
 		return;
 	s->hdlctx.slotcnt = s->ch_params.slottime;
-	if (prandom_u32_max(256) > s->ch_params.ppersist)
+	if (get_random_u8() > s->ch_params.ppersist)
 		return;
 	start_tx(dev, s);
 }

drivers/net/hamradio/yam.c

···
 	yp->slotcnt = yp->slot / 10;
 
 	/* is random > persist ? */
-	if (prandom_u32_max(256) > yp->pers)
+	if (get_random_u8() > yp->pers)
 		return;
 
 	yam_start_tx(dev, yp);

drivers/net/wireguard/selftest/allowedips.c

···
 			for (k = 0; k < 4; ++k)
 				mutated[k] = (mutated[k] & mutate_mask[k]) |
 					     (~mutate_mask[k] &
-					      prandom_u32_max(256));
+					      get_random_u8());
 			cidr = prandom_u32_max(32) + 1;
 			peer = peers[prandom_u32_max(NUM_PEERS)];
 			if (wg_allowedips_insert_v4(&t,
···
 			for (k = 0; k < 4; ++k)
 				mutated[k] = (mutated[k] & mutate_mask[k]) |
 					     (~mutate_mask[k] &
-					      prandom_u32_max(256));
+					      get_random_u8());
 			cidr = prandom_u32_max(128) + 1;
 			peer = peers[prandom_u32_max(NUM_PEERS)];
 			if (wg_allowedips_insert_v6(&t,

drivers/net/wireless/st/cw1200/wsm.c

···
 		edca = &priv->edca.params[i];
 		score = ((edca->aifns + edca->cwmin) << 16) +
 			((edca->cwmax - edca->cwmin) *
-			 (get_random_int() & 0xFFFF));
+			 get_random_u16());
 		if (score < best && (winner < 0 || i != 3)) {
 			best = score;
 			winner = i;

drivers/scsi/lpfc/lpfc_hbadisc.c

···
  * This function makes an running random selection decision on FCF record to
  * use through a sequence of @fcf_cnt eligible FCF records with equal
  * probability. To perform integer manunipulation of random numbers with
- * size unit32_t, the lower 16 bits of the 32-bit random number returned
- * from prandom_u32() are taken as the random random number generated.
+ * size unit32_t, a 16-bit random number returned from get_random_u16() is
+ * taken as the random random number generated.
  *
  * Returns true when outcome is for the newly read FCF record should be
  * chosen; otherwise, return false when outcome is for keeping the previously
···
 	uint32_t rand_num;
 
 	/* Get 16-bit uniform random number */
-	rand_num = 0xFFFF & prandom_u32();
+	rand_num = get_random_u16();
 
 	/* Decision with probability 1/fcf_cnt */
 	if ((fcf_cnt * rand_num) < 0xFFFF)

lib/cmdline_kunit.c

···
 		int rc = cmdline_test_values[i];
 		int offset;
 
-		sprintf(in, "%u%s", get_random_int() % 256, str);
+		sprintf(in, "%u%s", get_random_u8(), str);
 		/* Only first '-' after the number will advance the pointer */
 		offset = strlen(in) - strlen(str) + !!(rc == 2);
 		cmdline_do_one_test(test, in, rc, offset);
···
 		int rc = strcmp(str, "") ? (strcmp(str, "-") ? 0 : 1) : 1;
 		int offset;
 
-		sprintf(in, "%s%u", str, get_random_int() % 256);
+		sprintf(in, "%s%u", str, get_random_u8());
 		/*
 		 * Only first and leading '-' not followed by integer
 		 * will advance the pointer.

net/dccp/ipv4.c

···
 						    inet->inet_daddr,
 						    inet->inet_sport,
 						    inet->inet_dport);
-	inet->inet_id = prandom_u32();
+	inet->inet_id = get_random_u16();
 
 	err = dccp_connect(sk);
 	rt = NULL;
···
 	RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
 	newinet->mc_index  = inet_iif(skb);
 	newinet->mc_ttl	   = ip_hdr(skb)->ttl;
-	newinet->inet_id   = prandom_u32();
+	newinet->inet_id   = get_random_u16();
 
 	if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
 		goto put_and_exit;

net/ipv4/datagram.c

···
 	reuseport_has_conns(sk, true);
 	sk->sk_state = TCP_ESTABLISHED;
 	sk_set_txhash(sk);
-	inet->inet_id = prandom_u32();
+	inet->inet_id = get_random_u16();
 
 	sk_dst_set(sk, &rt->dst);
 	err = 0;

net/ipv4/ip_output.c

···
 		 * Avoid using the hashed IP ident generator.
 		 */
 		if (sk->sk_protocol == IPPROTO_TCP)
-			iph->id = (__force __be16)prandom_u32();
+			iph->id = (__force __be16)get_random_u16();
 		else
 			__ip_select_ident(net, iph, 1);
 	}

net/ipv4/tcp_ipv4.c

···
 						 inet->inet_daddr);
 	}
 
-	inet->inet_id = prandom_u32();
+	inet->inet_id = get_random_u16();
 
 	if (tcp_fastopen_defer_connect(sk, &err))
 		return err;
···
 	inet_csk(newsk)->icsk_ext_hdr_len = 0;
 	if (inet_opt)
 		inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
-	newinet->inet_id = prandom_u32();
+	newinet->inet_id = get_random_u16();
 
 	/* Set ToS of the new socket based upon the value of incoming SYN.
 	 * ECT bits are set later in tcp_init_transfer().

net/mac80211/scan.c

···
 		if (flags & IEEE80211_PROBE_FLAG_RANDOM_SN) {
 			struct ieee80211_hdr *hdr = (void *)skb->data;
 			struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
-			u16 sn = get_random_u32();
+			u16 sn = get_random_u16();
 
 			info->control.flags |= IEEE80211_TX_CTRL_NO_SEQNO;
 			hdr->seq_ctrl =

net/netfilter/nf_nat_core.c

···
 	if (range->flags & NF_NAT_RANGE_PROTO_OFFSET)
 		off = (ntohs(*keyptr) - ntohs(range->base_proto.all));
 	else
-		off = prandom_u32();
+		off = get_random_u16();
 
 	attempts = range_size;
 	if (attempts > max_attempts)
···
 	if (attempts >= range_size || attempts < 16)
 		return;
 	attempts /= 2;
-	off = prandom_u32();
+	off = get_random_u16();
 	goto another_round;
 }
 

net/sched/sch_cake.c

···
 
 		WARN_ON(host_load > CAKE_QUEUES);
 
-		/* The shifted prandom_u32() is a way to apply dithering to
-		 * avoid accumulating roundoff errors
+		/* The get_random_u16() is a way to apply dithering to avoid
+		 * accumulating roundoff errors
 		 */
 		flow->deficit += (b->flow_quantum * quantum_div[host_load] +
-				  (prandom_u32() >> 16)) >> 16;
+				  get_random_u16()) >> 16;
 		list_move_tail(&flow->flowchain, &b->old_flows);
 
 		goto retry;

net/sctp/socket.c

···
 	newinet->inet_rcv_saddr = inet->inet_rcv_saddr;
 	newinet->inet_dport = htons(asoc->peer.port);
 	newinet->pmtudisc = inet->pmtudisc;
-	newinet->inet_id = prandom_u32();
+	newinet->inet_id = get_random_u16();
 
 	newinet->uc_ttl = inet->uc_ttl;
 	newinet->mc_loop = 1;