treewide: use get_random_{u8,u16}() when possible, part 2

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 by hand,
identifying all of the places where one of the random integer functions
was used in a non-32-bit context.

Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Yury Norov <[email protected]>
Acked-by: Jakub Kicinski <[email protected]>
Acked-by: Heiko Carstens <[email protected]> # for s390
Signed-off-by: Jason A. Donenfeld <[email protected]>

Author: zx2c4

arch/s390/kernel/process.c

@@ -230,7 +230,7 @@ unsigned long arch_align_stack(unsigned long sp)
 
 static inline unsigned long brk_rnd(void)
 {
-	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
+	return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT;
 }
 
 unsigned long arch_randomize_brk(struct mm_struct *mm)

drivers/mtd/nand/raw/nandsim.c

@@ -1402,7 +1402,7 @@ static int ns_do_read_error(struct nandsim *ns, int num)
 
 static void ns_do_bit_flips(struct nandsim *ns, int num)
 {
-	if (bitflips && prandom_u32() < (1 << 22)) {
+	if (bitflips && get_random_u16() < (1 << 6)) {
 		int flips = 1;
 		if (bitflips > 1)
 			flips = prandom_u32_max(bitflips) + 1;

drivers/net/wireless/broadcom/brcm80211/brcmfmac/pno.c

@@ -177,7 +177,7 @@ static int brcmf_pno_set_random(struct brcmf_if *ifp, struct brcmf_pno_info *pi)
 	memcpy(pfn_mac.mac, mac_addr, ETH_ALEN);
 	for (i = 0; i < ETH_ALEN; i++) {
 		pfn_mac.mac[i] &= mac_mask[i];
-		pfn_mac.mac[i] |= get_random_int() & ~(mac_mask[i]);
+		pfn_mac.mac[i] |= get_random_u8() & ~(mac_mask[i]);
 	}
 	/* Clear multi bit */
 	pfn_mac.mac[0] &= 0xFE;

lib/test_vmalloc.c

@@ -80,7 +80,7 @@ static int random_size_align_alloc_test(void)
 	int i;
 
 	for (i = 0; i < test_loop_count; i++) {
-		rnd = prandom_u32();
+		rnd = get_random_u8();
 
 		/*
 		 * Maximum 1024 pages, if PAGE_SIZE is 4096.

net/rds/bind.c

@@ -104,7 +104,7 @@ static int rds_add_bound(struct rds_sock *rs, const struct in6_addr *addr,
 			return -EINVAL;
 		last = rover;
 	} else {
-		rover = max_t(u16, prandom_u32(), 2);
+		rover = max_t(u16, get_random_u16(), 2);
 		last = rover - 1;
 	}
 

net/sched/sch_sfb.c

@@ -379,7 +379,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		goto enqueue;
 	}
 
-	r = prandom_u32() & SFB_MAX_PROB;
+	r = get_random_u16() & SFB_MAX_PROB;
 
 	if (unlikely(r < p_min)) {
 		if (unlikely(p_min > SFB_MAX_PROB / 2)) {