Merge tag 'random-6.1-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random

Pull more random number generator updates from Jason Donenfeld:
 "This time with some large scale treewide cleanups.

  The intent of this pull is to clean up the way callers fetch random
  integers. The current rules for doing this right are:

   - If you want a secure or an insecure random u64, use get_random_u64()

   - If you want a secure or an insecure random u32, use get_random_u32()

     The old function prandom_u32() has been deprecated for a while
     now and is just a wrapper around get_random_u32(). Same for
     get_random_int().

   - If you want a secure or an insecure random u16, use get_random_u16()

   - If you want a secure or an insecure random u8, use get_random_u8()

   - If you want secure or insecure random bytes, use get_random_bytes().

     The old function prandom_bytes() has been deprecated for a while
     now and has long been a wrapper around get_random_bytes()

   - If you want a non-uniform random u32, u16, or u8 bounded by a
     certain open interval maximum, use prandom_u32_max()

     I say "non-uniform", because it doesn't do any rejection sampling
     or divisions. Hence, it stays within the prandom_*() namespace, not
     the get_random_*() namespace.

     I'm currently investigating a "uniform" function for 6.2. We'll see
     what comes of that.

  By applying these rules uniformly, we get several benefits:

   - By using prandom_u32_max() with an upper-bound that the compiler
     can prove at compile-time is ≤65536 or ≤256, internally
     get_random_u16() or get_random_u8() is used, which wastes fewer
     batched random bytes, and hence has higher throughput.

   - By using prandom_u32_max() instead of %, when the upper-bound is
     not a constant, division is still avoided, because
     prandom_u32_max() uses a faster multiplication-based trick instead.

   - By using get_random_u16() or get_random_u8() in cases where the
     return value is intended to indeed be a u16 or a u8, we waste fewer
     batched random bytes, and hence have higher throughput.

  This series was originally done by hand while I was on an airplane
  without Internet. Later, Kees and I worked on retroactively figuring
  out what could be done with Coccinelle and what had to be done
  manually, and then we split things up based on that.

  So while this touches a lot of files, the actual amount of code that's
  hand fiddled is comfortably small"

* tag 'random-6.1-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random:
  prandom: remove unused functions
  treewide: use get_random_bytes() when possible
  treewide: use get_random_u32() when possible
  treewide: use get_random_{u8,u16}() when possible, part 2
  treewide: use get_random_{u8,u16}() when possible, part 1
  treewide: use prandom_u32_max() when possible, part 2
  treewide: use prandom_u32_max() when possible, part 1

4 files changed, 11 insertions, 11 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 10ce86bf228e..417834b7169d 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -104,7 +104,7 @@ static inline u32 cstamp_delta(unsigned long cstamp)
 static inline s32 rfc3315_s14_backoff_init(s32 irt)
 {
 	/* multiply 'initial retransmission time' by 0.9 .. 1.1 */
-	u64 tmp = (900000 + prandom_u32() % 200001) * (u64)irt;
+	u64 tmp = (900000 + prandom_u32_max(200001)) * (u64)irt;
 	do_div(tmp, 1000000);
 	return (s32)tmp;
 }
@@ -112,11 +112,11 @@ static inline s32 rfc3315_s14_backoff_init(s32 irt)
 static inline s32 rfc3315_s14_backoff_update(s32 rt, s32 mrt)
 {
 	/* multiply 'retransmission timeout' by 1.9 .. 2.1 */
-	u64 tmp = (1900000 + prandom_u32() % 200001) * (u64)rt;
+	u64 tmp = (1900000 + prandom_u32_max(200001)) * (u64)rt;
 	do_div(tmp, 1000000);
 	if ((s32)tmp > mrt) {
 		/* multiply 'maximum retransmission time' by 0.9 .. 1.1 */
-		tmp = (900000 + prandom_u32() % 200001) * (u64)mrt;
+		tmp = (900000 + prandom_u32_max(200001)) * (u64)mrt;
 		do_div(tmp, 1000000);
 	}
 	return (s32)tmp;
@@ -3967,7 +3967,7 @@ static void addrconf_dad_kick(struct inet6_ifaddr *ifp)
 	if (ifp->flags & IFA_F_OPTIMISTIC)
 		rand_num = 0;
 	else
-		rand_num = prandom_u32() % (idev->cnf.rtr_solicit_delay ? : 1);
+		rand_num = prandom_u32_max(idev->cnf.rtr_solicit_delay ?: 1);
 
 	nonce = 0;
 	if (idev->cnf.enhanced_dad ||
diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
index ceb85c67ce39..18481eb76a0a 100644
--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -220,7 +220,7 @@ static struct ip6_flowlabel *fl_intern(struct net *net,
 	spin_lock_bh(&ip6_fl_lock);
 	if (label == 0) {
 		for (;;) {
-			fl->label = htonl(prandom_u32())&IPV6_FLOWLABEL_MASK;
+			fl->label = htonl(get_random_u32())&IPV6_FLOWLABEL_MASK;
 			if (fl->label) {
 				lfl = __fl_lookup(net, fl->label);
 				if (!lfl)
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 0566ab03ddbe..7860383295d8 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1050,7 +1050,7 @@ bool ipv6_chk_mcast_addr(struct net_device *dev, const struct in6_addr *group,
 /* called with mc_lock */
 static void mld_gq_start_work(struct inet6_dev *idev)
 {
-	unsigned long tv = prandom_u32() % idev->mc_maxdelay;
+	unsigned long tv = prandom_u32_max(idev->mc_maxdelay);
 
 	idev->mc_gq_running = 1;
 	if (!mod_delayed_work(mld_wq, &idev->mc_gq_work, tv + 2))
@@ -1068,7 +1068,7 @@ static void mld_gq_stop_work(struct inet6_dev *idev)
 /* called with mc_lock */
 static void mld_ifc_start_work(struct inet6_dev *idev, unsigned long delay)
 {
-	unsigned long tv = prandom_u32() % delay;
+	unsigned long tv = prandom_u32_max(delay);
 
 	if (!mod_delayed_work(mld_wq, &idev->mc_ifc_work, tv + 2))
 		in6_dev_hold(idev);
@@ -1085,7 +1085,7 @@ static void mld_ifc_stop_work(struct inet6_dev *idev)
 /* called with mc_lock */
 static void mld_dad_start_work(struct inet6_dev *idev, unsigned long delay)
 {
-	unsigned long tv = prandom_u32() % delay;
+	unsigned long tv = prandom_u32_max(delay);
 
 	if (!mod_delayed_work(mld_wq, &idev->mc_dad_work, tv + 2))
 		in6_dev_hold(idev);
@@ -1130,7 +1130,7 @@ static void igmp6_group_queried(struct ifmcaddr6 *ma, unsigned long resptime)
 	}
 
 	if (delay >= resptime)
-		delay = prandom_u32() % resptime;
+		delay = prandom_u32_max(resptime);
 
 	if (!mod_delayed_work(mld_wq, &ma->mca_work, delay))
 		refcount_inc(&ma->mca_refcnt);
@@ -2574,7 +2574,7 @@ static void igmp6_join_group(struct ifmcaddr6 *ma)
 
 	igmp6_send(&ma->mca_addr, ma->idev->dev, ICMPV6_MGM_REPORT);
 
-	delay = prandom_u32() % unsolicited_report_interval(ma->idev);
+	delay = prandom_u32_max(unsolicited_report_interval(ma->idev));
 
 	if (cancel_delayed_work(&ma->mca_work)) {
 		refcount_dec(&ma->mca_refcnt);
diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
index 2880dc7d9a49..2685c3f15e9d 100644
--- a/net/ipv6/output_core.c
+++ b/net/ipv6/output_core.c
@@ -18,7 +18,7 @@ static u32 __ipv6_select_ident(struct net *net,
 	u32 id;
 
 	do {
-		id = prandom_u32();
+		id = get_random_u32();
 	} while (!id);
 
 	return id;