From e8a533cbeb79809206f8724e89961e0079508c3c Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sun, 9 Oct 2022 20:44:02 -0600
Subject: treewide: use get_random_u32_inclusive() when possible

These cases were done with this Coccinelle:

@@
expression H;
expression L;
@@
- (get_random_u32_below(H) + L)
+ get_random_u32_inclusive(L, H + L - 1)

@@
expression H;
expression L;
expression E;
@@
  get_random_u32_inclusive(L,
  H
- + E
- - E
  )

@@
expression H;
expression L;
expression E;
@@
  get_random_u32_inclusive(L,
  H
- - E
- + E
  )

@@
expression H;
expression L;
expression E;
expression F;
@@
  get_random_u32_inclusive(L,
  H
- - E
  + F
- + E
  )

@@
expression H;
expression L;
expression E;
expression F;
@@
  get_random_u32_inclusive(L,
  H
- + E
  + F
- - E
  )

And then subsequently cleaned up by hand, with several automatic cases
rejected if it didn't make sense contextually.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> # for infiniband
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 mm/kasan/kasan_test.c   | 6 +++---
 mm/kfence/kfence_test.c | 2 +-
 mm/swapfile.c           | 5 ++---
 3 files changed, 6 insertions(+), 7 deletions(-)

(limited to 'mm')

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 640f9c7f8e44..54181eba3e24 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -1299,7 +1299,7 @@ static void match_all_not_assigned(struct kunit *test)
 	KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
 
 	for (i = 0; i < 256; i++) {
-		size = get_random_u32_below(1024) + 1;
+		size = get_random_u32_inclusive(1, 1024);
 		ptr = kmalloc(size, GFP_KERNEL);
 		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 		KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);
@@ -1308,7 +1308,7 @@ static void match_all_not_assigned(struct kunit *test)
 	}
 
 	for (i = 0; i < 256; i++) {
-		order = get_random_u32_below(4) + 1;
+		order = get_random_u32_inclusive(1, 4);
 		pages = alloc_pages(GFP_KERNEL, order);
 		ptr = page_address(pages);
 		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -1321,7 +1321,7 @@ static void match_all_not_assigned(struct kunit *test)
 		return;
 
 	for (i = 0; i < 256; i++) {
-		size = get_random_u32_below(1024) + 1;
+		size = get_random_u32_inclusive(1, 1024);
 		ptr = vmalloc(size);
 		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 		KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);
diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
index 20028c179796..b5d66a69200d 100644
--- a/mm/kfence/kfence_test.c
+++ b/mm/kfence/kfence_test.c
@@ -532,7 +532,7 @@ static void test_free_bulk(struct kunit *test)
 	int iter;
 
 	for (iter = 0; iter < 5; iter++) {
-		const size_t size = setup_test_cache(test, 8 + get_random_u32_below(300),
+		const size_t size = setup_test_cache(test, get_random_u32_inclusive(8, 307),
 						     0, (iter & 1) ? ctor_set_x : NULL);
 		void *objects[] = {
 			test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT),
diff --git a/mm/swapfile.c b/mm/swapfile.c
index e9318305a24a..4ee31056d3f8 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -772,8 +772,7 @@ static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
 		/* No free swap slots available */
 		if (si->highest_bit <= si->lowest_bit)
 			return;
-		next = si->lowest_bit +
-			get_random_u32_below(si->highest_bit - si->lowest_bit + 1);
+		next = get_random_u32_inclusive(si->lowest_bit, si->highest_bit);
 		next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
 		next = max_t(unsigned int, next, si->lowest_bit);
 	}
@@ -3089,7 +3088,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		 */
 		for_each_possible_cpu(cpu) {
 			per_cpu(*p->cluster_next_cpu, cpu) =
-				1 + get_random_u32_below(p->highest_bit);
+				get_random_u32_inclusive(1, p->highest_bit);
 		}
 		nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
 
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