From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: linux-kernel@vger.kernel.org, patches@lists.linux.dev
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
"Andreas Noever" <andreas.noever@gmail.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Borislav Petkov" <bp@alien8.de>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Christoph Böhmwalder" <christoph.boehmwalder@linbit.com>,
"Christoph Hellwig" <hch@lst.de>,
"Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Dave Airlie" <airlied@redhat.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"David S . Miller" <davem@davemloft.net>,
"Eric Dumazet" <edumazet@google.com>,
"Florian Westphal" <fw@strlen.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"H . Peter Anvin" <hpa@zytor.com>,
"Heiko Carstens" <hca@linux.ibm.com>,
"Helge Deller" <deller@gmx.de>,
"Herbert Xu" <herbert@gondor.apana.org.au>,
"Huacai Chen" <chenhuacai@kernel.org>,
"Hugh Dickins" <hughd@google.com>,
"Jakub Kicinski" <kuba@kernel.org>,
"James E . J . Bottomley" <jejb@linux.ibm.com>,
"Jan Kara" <jack@suse.com>, "Jason Gunthorpe" <jgg@ziepe.ca>,
"Jens Axboe" <axboe@kernel.dk>,
"Johannes Berg" <johannes@sipsolutions.net>,
"Jonathan Corbet" <corbet@lwn.net>,
"Jozsef Kadlecsik" <kadlec@netfilter.org>,
"KP Singh" <kpsingh@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Marco Elver" <elver@google.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Pablo Neira Ayuso" <pablo@netfilter.org>,
"Paolo Abeni" <pabeni@redhat.com>,
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"Vignesh Raghavendra" <vigneshr@ti.com>,
"WANG Xuerui" <kernel@xen0n.name>,
"Will Deacon" <will@kernel.org>,
"Yury Norov" <yury.norov@gmail.com>,
dri-devel@lists.freedesktop.org, kasan-dev@googlegroups.com,
kernel-janitors@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
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netdev@vger.kernel.org, sparclinux@vger.kernel.org,
x86@kernel.org, "Jan Kara" <jack@suse.cz>
Subject: [PATCH v5 2/7] treewide: use prandom_u32_max() when possible, part 2
Date: Fri, 7 Oct 2022 23:53:54 -0600 [thread overview]
Message-ID: <20221008055359.286426-3-Jason@zx2c4.com> (raw)
In-Reply-To: <20221008055359.286426-1-Jason@zx2c4.com>
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@chromium.org>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext2, ext4, and sbitmap
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.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
next prev parent reply other threads:[~2022-10-08 5:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-08 5:53 [PATCH v5 0/7] treewide cleanup of random integer usage Jason A. Donenfeld
2022-10-08 5:53 ` [PATCH v5 1/7] treewide: use prandom_u32_max() when possible, part 1 Jason A. Donenfeld
2022-10-08 5:53 ` Jason A. Donenfeld [this message]
2022-10-08 5:53 ` [PATCH v5 3/7] treewide: use get_random_{u8,u16}() " Jason A. Donenfeld
2022-10-08 5:53 ` [PATCH v5 4/7] treewide: use get_random_{u8,u16}() when possible, part 2 Jason A. Donenfeld
2022-10-08 5:53 ` [PATCH v5 5/7] treewide: use get_random_u32() when possible Jason A. Donenfeld
2022-10-08 5:53 ` [PATCH v5 6/7] treewide: use get_random_bytes " Jason A. Donenfeld
2022-10-08 5:53 ` [PATCH v5 7/7] prandom: remove unused functions Jason A. Donenfeld
2022-10-08 15:38 ` [PATCH v5 0/7] treewide cleanup of random integer usage Greg Kroah-Hartman
2022-10-08 21:42 ` Yury Norov
2022-10-09 3:41 ` Kees Cook
2022-10-09 14:17 ` Jason A. Donenfeld
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