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Message-Id: <20221008055359.286426-3-Jason@zx2c4.com>
Date: Fri, 7 Oct 2022 23:53:54 -0600
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Cc: "Jason A. Donenfeld" <Jason@...c4.com>,
Andreas Noever <andreas.noever@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Christoph Böhmwalder
<christoph.boehmwalder@...bit.com>, Christoph Hellwig <hch@....de>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Daniel Borkmann <daniel@...earbox.net>,
Dave Airlie <airlied@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Florian Westphal <fw@...len.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"H . Peter Anvin" <hpa@...or.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Helge Deller <deller@....de>,
Herbert Xu <herbert@...dor.apana.org.au>,
Huacai Chen <chenhuacai@...nel.org>,
Hugh Dickins <hughd@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
"James E . J . Bottomley" <jejb@...ux.ibm.com>,
Jan Kara <jack@...e.com>, Jason Gunthorpe <jgg@...pe.ca>,
Jens Axboe <axboe@...nel.dk>,
Johannes Berg <johannes@...solutions.net>,
Jonathan Corbet <corbet@....net>,
Jozsef Kadlecsik <kadlec@...filter.org>,
KP Singh <kpsingh@...nel.org>,
Kees Cook <keescook@...omium.org>,
Marco Elver <elver@...gle.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
Pablo Neira Ayuso <pablo@...filter.org>,
Paolo Abeni <pabeni@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Richard Weinberger <richard@....at>,
Russell King <linux@...linux.org.uk>,
Theodore Ts'o <tytso@....edu>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Thomas Graf <tgraf@...g.ch>,
Ulf Hansson <ulf.hansson@...aro.org>,
Vignesh Raghavendra <vigneshr@...com>,
WANG Xuerui <kernel@...0n.name>, Will Deacon <will@...nel.org>,
Yury Norov <yury.norov@...il.com>,
dri-devel@...ts.freedesktop.org, kasan-dev@...glegroups.com,
kernel-janitors@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-block@...r.kernel.org,
linux-crypto@...r.kernel.org, linux-doc@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-media@...r.kernel.org,
linux-mips@...r.kernel.org, linux-mm@...ck.org,
linux-mmc@...r.kernel.org, linux-mtd@...ts.infradead.org,
linux-nvme@...ts.infradead.org, linux-parisc@...r.kernel.org,
linux-rdma@...r.kernel.org, linux-s390@...r.kernel.org,
linux-um@...ts.infradead.org, linux-usb@...r.kernel.org,
linux-wireless@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
loongarch@...ts.linux.dev, netdev@...r.kernel.org,
sparclinux@...r.kernel.org, x86@...nel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH v5 2/7] 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: Kees Cook <keescook@...omium.org>
Reviewed-by: Jan Kara <jack@...e.cz> # for ext2, ext4, and sbitmap
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
fs/ext2/ialloc.c | 3 +--
fs/ext4/ialloc.c | 5 ++---
lib/sbitmap.c | 2 +-
lib/test_vmalloc.c | 17 ++++-------------
4 files changed, 8 insertions(+), 19 deletions(-)
diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index 998dd2ac8008..f4944c4dee60 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c
@@ -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);
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index f73e5eb43eae..36d5bc595cc2 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -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);
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index c4f04edf3ee9..ef0661504561 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -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;
}
diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
index 4f2f2d1bac56..a26bbbf20e62 100644
--- a/lib/test_vmalloc.c
+++ b/lib/test_vmalloc.c
@@ -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]);
--
2.37.3
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