treewide: use get_random_u32_{above,below}() instead of manual loop

These cases were done with this Coccinelle:

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I > E);
+   I = get_random_u32_below(E + 1);

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I >= E);
+   I = get_random_u32_below(E);

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I < E);
+   I = get_random_u32_above(E - 1);

@@
expression E;
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I <= E);
+   I = get_random_u32_above(E);

@@
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (!I);
+   I = get_random_u32_above(0);

@@
identifier I;
@@
-   do {
      ... when != I
-     I = get_random_u32();
      ... when != I
-   } while (I == 0);
+   I = get_random_u32_above(0);

@@
expression E;
@@
- E + 1 + get_random_u32_below(U32_MAX - E)
+ get_random_u32_above(E)

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

fs/ext4/mmp.c

@@ -262,13 +262,7 @@ void ext4_stop_mmpd(struct ext4_sb_info *sbi)
  */
 static unsigned int mmp_new_seq(void)
 {
-	u32 new_seq;
-
-	do {
-		new_seq = get_random_u32();
-	} while (new_seq > EXT4_MMP_SEQ_MAX);
-
-	return new_seq;
+	return get_random_u32_below(EXT4_MMP_SEQ_MAX + 1);
 }
 
 /*

lib/test_fprobe.c

@@ -144,10 +144,7 @@ static unsigned long get_ftrace_location(void *func)
 
 static int fprobe_test_init(struct kunit *test)
 {
-	do {
-		rand1 = get_random_u32();
-	} while (rand1 <= div_factor);
-
+	rand1 = get_random_u32_above(div_factor);
 	target = fprobe_selftest_target;
 	target2 = fprobe_selftest_target2;
 	target_ip = get_ftrace_location(target);

lib/test_kprobes.c

@@ -339,10 +339,7 @@ static int kprobes_test_init(struct kunit *test)
 	stacktrace_target = kprobe_stacktrace_target;
 	internal_target = kprobe_stacktrace_internal_target;
 	stacktrace_driver = kprobe_stacktrace_driver;
-
-	do {
-		rand1 = get_random_u32();
-	} while (rand1 <= div_factor);
+	rand1 = get_random_u32_above(div_factor);
 	return 0;
 }
 

net/ipv6/output_core.c

@@ -15,13 +15,7 @@ static u32 __ipv6_select_ident(struct net *net,
 			       const struct in6_addr *dst,
 			       const struct in6_addr *src)
 {
-	u32 id;
-
-	do {
-		id = get_random_u32();
-	} while (!id);
-
-	return id;
+	return get_random_u32_above(0);
 }
 
 /* This function exists only for tap drivers that must support broken

net/vmw_vsock/af_vsock.c

@@ -626,8 +626,7 @@ static int __vsock_bind_connectible(struct vsock_sock *vsk,
 	struct sockaddr_vm new_addr;
 
 	if (!port)
-		port = LAST_RESERVED_PORT + 1 +
-			get_random_u32_below(U32_MAX - LAST_RESERVED_PORT);
+		port = get_random_u32_above(LAST_RESERVED_PORT);
 
 	vsock_addr_init(&new_addr, addr->svm_cid, addr->svm_port);