Commit 8b3ccbc1 authored by Jason A. Donenfeld's avatar Jason A. Donenfeld
Browse files

treewide: use prandom_u32_max() when possible, part 2 



Rather than incurring a division or requesting too many random bytes for
the given range, use the prandom_u32_max() function, which only takes
the minimum required bytes from the RNG and avoids divisions. This was
done by hand, covering things that coccinelle could not do on its own.

Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarYury Norov <yury.norov@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext2, ext4, and sbitmap
Acked-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
parent 81895a65

fs/ext2/ialloc.c

+1 −2
Original line number Diff line number Diff line
@@ -277,8 +277,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent) 
		int best_ndir = inodes_per_group;

		int best_group = -1;



		group = prandom_u32();

		parent_group = (unsigned)group % ngroups;

		parent_group = prandom_u32_max(ngroups);

		for (i = 0; i < ngroups; i++) {

			group = (parent_group + i) % ngroups;

			desc = ext2_get_group_desc (sb, group, NULL);

fs/ext4/ialloc.c

+2 −3
Original line number Diff line number Diff line
@@ -463,10 +463,9 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent, 
			hinfo.hash_version = DX_HASH_HALF_MD4;

			hinfo.seed = sbi->s_hash_seed;

			ext4fs_dirhash(parent, qstr->name, qstr->len, &hinfo);

			grp = hinfo.hash;

			parent_group = hinfo.hash % ngroups;

		} else

			grp = prandom_u32();

		parent_group = (unsigned)grp % ngroups;

			parent_group = prandom_u32_max(ngroups);

		for (i = 0; i < ngroups; i++) {

			g = (parent_group + i) % ngroups;

			get_orlov_stats(sb, g, flex_size, &stats);

lib/sbitmap.c

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ static int init_alloc_hint(struct sbitmap *sb, gfp_t flags) 
		int i;



		for_each_possible_cpu(i)

			*per_cpu_ptr(sb->alloc_hint, i) = prandom_u32() % depth;

			*per_cpu_ptr(sb->alloc_hint, i) = prandom_u32_max(depth);

	}

	return 0;

}

lib/test_vmalloc.c

+4 −13
Original line number Diff line number Diff line
@@ -151,9 +151,7 @@ static int random_size_alloc_test(void) 
	int i;



	for (i = 0; i < test_loop_count; i++) {

		n = prandom_u32();

		n = (n % 100) + 1;



		n = prandom_u32_max(100) + 1;

		p = vmalloc(n * PAGE_SIZE);



		if (!p)
@@ -293,16 +291,12 @@ pcpu_alloc_test(void) 
		return -1;



	for (i = 0; i < 35000; i++) {

		unsigned int r;



		r = prandom_u32();

		size = (r % (PAGE_SIZE / 4)) + 1;

		size = prandom_u32_max(PAGE_SIZE / 4) + 1;



		/*

		 * Maximum PAGE_SIZE

		 */

		r = prandom_u32();

		align = 1 << ((r % 11) + 1);

		align = 1 << (prandom_u32_max(11) + 1);



		pcpu[i] = __alloc_percpu(size, align);

		if (!pcpu[i])
@@ -393,14 +387,11 @@ static struct test_driver { 


static void shuffle_array(int *arr, int n)

{

	unsigned int rnd;

	int i, j;



	for (i = n - 1; i > 0; i--)  {

		rnd = prandom_u32();



		/* Cut the range. */

		j = rnd % i;

		j = prandom_u32_max(i);



		/* Swap indexes. */

		swap(arr[i], arr[j]);