diff mbox series

[v2,3/3] treewide: use get_random_u32_between() when possible

Message ID 20221114164558.1180362-4-Jason@zx2c4.com (mailing list archive)
State Handled Elsewhere
Headers show
Series convert tree to get_random_u32_{below,above,between}() | expand

Commit Message

Jason A. Donenfeld Nov. 14, 2022, 4:45 p.m. UTC 
These cases were done with this Coccinelle:

@@
expression H;
expression L;
@@
- (get_random_u32_below(H) + L)
+ get_random_u32_between(L, H + L)

@@
expression H;
expression L;
expression E;
@@
  get_random_u32_between(L,
  H
- + E
- - E
  )

@@
expression H;
expression L;
expression E;
@@
  get_random_u32_between(L,
  H
- - E
- + E
  )

@@
expression H;
expression L;
expression E;
expression F;
@@
  get_random_u32_between(L,
  H
- - E
  + F
- + E
  )

@@
expression H;
expression L;
expression E;
expression F;
@@
  get_random_u32_between(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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> # for infiniband
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 arch/x86/kernel/module.c                      |  2 +-
 crypto/rsa-pkcs1pad.c                         |  2 +-
 crypto/testmgr.c                              | 10 ++++----
 drivers/bus/mhi/host/internal.h               |  2 +-
 drivers/dma-buf/st-dma-fence-chain.c          |  2 +-
 drivers/infiniband/core/cma.c                 |  2 +-
 drivers/infiniband/hw/hns/hns_roce_ah.c       |  5 ++--
 drivers/mtd/nand/raw/nandsim.c                |  2 +-
 drivers/net/wireguard/selftest/allowedips.c   |  8 +++---
 .../broadcom/brcm80211/brcmfmac/p2p.c         |  2 +-
 .../net/wireless/intel/iwlwifi/mvm/mac-ctxt.c |  2 +-
 fs/f2fs/segment.c                             |  6 ++---
 kernel/kcsan/selftest.c                       |  2 +-
 lib/test_hexdump.c                            | 10 ++++----
 lib/test_printf.c                             |  2 +-
 lib/test_vmalloc.c                            |  6 ++---
 mm/kasan/kasan_test.c                         |  6 ++---
 mm/kfence/kfence_test.c                       |  2 +-
 mm/swapfile.c                                 |  5 ++--
 net/bluetooth/mgmt.c                          |  5 ++--
 net/core/pktgen.c                             | 25 ++++++++-----------
 net/ipv4/tcp_input.c                          |  2 +-
 net/ipv6/addrconf.c                           |  6 ++---
 net/netfilter/nf_nat_helper.c                 |  2 +-
 net/xfrm/xfrm_state.c                         |  2 +-
 25 files changed, 56 insertions(+), 64 deletions(-)

Comments

Kees Cook Nov. 16, 2022, 10:43 p.m. UTC | #1 
On Mon, Nov 14, 2022 at 05:45:58PM +0100, Jason A. Donenfeld wrote:
> -				(get_random_u32_below(1024) + 1) * PAGE_SIZE;
> +				get_random_u32_between(1, 1024 + 1) * PAGE_SIZE;

I really don't like "between". Can't this be named "inclusive" (and
avoid adding 1 everywhere, which seems ugly), or at least named
something less ambiguous?

> -		n = get_random_u32_below(100) + 1;
> +		n = get_random_u32_between(1, 101);

Because I find this much less readable. "Below 100" is clear: 0-99
inclusive, plus 1, so 1-100 inclusive. "Between 1 and 101" is not obvious
to me to mean: 1-100 inclusive.

These seem so much nicer:
	get_random_u32_inclusive(1, 1024)
	get_random_u32_inclusive(1, 100)
Jason A. Donenfeld Nov. 16, 2022, 11:55 p.m. UTC | #2 
On Wed, Nov 16, 2022 at 02:43:13PM -0800, Kees Cook wrote:
> On Mon, Nov 14, 2022 at 05:45:58PM +0100, Jason A. Donenfeld wrote:
> > -				(get_random_u32_below(1024) + 1) * PAGE_SIZE;
> > +				get_random_u32_between(1, 1024 + 1) * PAGE_SIZE;
> 
> I really don't like "between". Can't this be named "inclusive" (and
> avoid adding 1 everywhere, which seems ugly), or at least named
> something less ambiguous?
> 
> > -		n = get_random_u32_below(100) + 1;
> > +		n = get_random_u32_between(1, 101);
> 
> Because I find this much less readable. "Below 100" is clear: 0-99
> inclusive, plus 1, so 1-100 inclusive. "Between 1 and 101" is not obvious
> to me to mean: 1-100 inclusive.
> 
> These seem so much nicer:
> 	get_random_u32_inclusive(1, 1024)
> 	get_random_u32_inclusive(1, 100)

Yann pointed out something similar -- the half-closed interval being
confusing -- and while I was initially dismissive, I've warmed up to
doing this fully closed after sending a diff of that:

https://lore.kernel.org/lkml/Y3Qt8HiXj8giOnZy@zx2c4.com/

So okay, let's say that I'll implement the inclusive version instead. We
now have two problems to solve:

1) How/whether to make f(0, UR2_MAX) safe,
   - without additional 64-bit arithmetic,
   - minimizing the number of branches.
   I have a few ideas I'll code golf for a bit.

2) What to call it:
   - between I still like, because it mirrors "I'm thinking of a number
     between 1 and 10 and..." that everybody knows,
   - inclusive I guess works, but it's not a preposition,
   - bikeshed color #3?

I think I can make progress with (1) alone by fiddling around with
godbolt enough, like usual. I could use some more ideas for (2) though.

Jason
Jason A. Donenfeld Nov. 17, 2022, 12:03 a.m. UTC | #3 
On Thu, Nov 17, 2022 at 12:55:47AM +0100, Jason A. Donenfeld wrote:
> 2) What to call it:
>    - between I still like, because it mirrors "I'm thinking of a number
>      between 1 and 10 and..." that everybody knows,
>    - inclusive I guess works, but it's not a preposition,
>    - bikeshed color #3?

- between
- ranged
- spanning

https://www.thefreedictionary.com/List-of-prepositions.htm
- amid

Sigh, names.
Kees Cook Nov. 17, 2022, 12:31 a.m. UTC | #4 
On Thu, Nov 17, 2022 at 01:03:14AM +0100, Jason A. Donenfeld wrote:
> On Thu, Nov 17, 2022 at 12:55:47AM +0100, Jason A. Donenfeld wrote:
> > 2) What to call it:
> >    - between I still like, because it mirrors "I'm thinking of a number
> >      between 1 and 10 and..." that everybody knows,
> >    - inclusive I guess works, but it's not a preposition,
> >    - bikeshed color #3?
> 
> - between
> - ranged
> - spanning
> 
> https://www.thefreedictionary.com/List-of-prepositions.htm
> - amid
> 
> Sigh, names.

I think "inclusive" is best. The other words still don't provide
unambiguous language. It's the language used in formal math, e.g.
sigma-notation, etc. It's an adjective for "get random" (verb, noun).
Jason A. Donenfeld Nov. 17, 2022, 12:43 a.m. UTC | #5 
On Wed, Nov 16, 2022 at 04:31:18PM -0800, Kees Cook wrote:
> On Thu, Nov 17, 2022 at 01:03:14AM +0100, Jason A. Donenfeld wrote:
> > On Thu, Nov 17, 2022 at 12:55:47AM +0100, Jason A. Donenfeld wrote:
> > > 2) What to call it:
> > >    - between I still like, because it mirrors "I'm thinking of a number
> > >      between 1 and 10 and..." that everybody knows,
> > >    - inclusive I guess works, but it's not a preposition,
> > >    - bikeshed color #3?
> > 
> > - between
> > - ranged
> > - spanning
> > 
> > https://www.thefreedictionary.com/List-of-prepositions.htm
> > - amid
> > 
> > Sigh, names.
> 
> I think "inclusive" is best.

I find it not very descriptive of what the function does. Is there one
you like second best? Or are you convinced they're all much much much
worse than "inclusive" that they shouldn't be considered?

Jason
Kees Cook Nov. 17, 2022, 12:47 a.m. UTC | #6 
On November 16, 2022 4:43:54 PM PST, "Jason A. Donenfeld" <Jason@zx2c4.com> wrote:
>On Wed, Nov 16, 2022 at 04:31:18PM -0800, Kees Cook wrote:
>> On Thu, Nov 17, 2022 at 01:03:14AM +0100, Jason A. Donenfeld wrote:
>> > On Thu, Nov 17, 2022 at 12:55:47AM +0100, Jason A. Donenfeld wrote:
>> > > 2) What to call it:
>> > >    - between I still like, because it mirrors "I'm thinking of a number
>> > >      between 1 and 10 and..." that everybody knows,
>> > >    - inclusive I guess works, but it's not a preposition,
>> > >    - bikeshed color #3?
>> > 
>> > - between
>> > - ranged
>> > - spanning
>> > 
>> > https://www.thefreedictionary.com/List-of-prepositions.htm
>> > - amid
>> > 
>> > Sigh, names.
>> 
>> I think "inclusive" is best.
>
>I find it not very descriptive of what the function does. Is there one
>you like second best? Or are you convinced they're all much much much
>worse than "inclusive" that they shouldn't be considered?

Right, I don't think any are sufficiently descriptive. "Incluisve" with two arguments seems unambiguous and complete to me. :)
Jason A. Donenfeld Nov. 17, 2022, 2:05 a.m. UTC | #7 
On Thu, Nov 17, 2022 at 12:55:47AM +0100, Jason A. Donenfeld wrote:
> 1) How/whether to make f(0, UR2_MAX) safe,
>    - without additional 64-bit arithmetic,
>    - minimizing the number of branches.
>    I have a few ideas I'll code golf for a bit.
> I think I can make progress with (1) alone by fiddling around with
> godbolt enough, like usual.

The code gen is definitely worse.

Original half-open interval:

    return floor + get_random_u32_below(ceil - floor);

Suggested fully closed interval:
	
    ceil = ceil - floor + 1;
    return likely(ceil) ? floor + get_random_u32_below(ceil) : get_random_u32();

Is the worse code gen actually worth it? Options:

 a) Decide worse codegen is worth it.
 b) Declare f(0, U32_MAX) undefined and just not handle it.
 c) Stick with original half-open interval that doesn't have this problem.

Jason
Russell King (Oracle) Nov. 17, 2022, 10:32 a.m. UTC | #8 
On Thu, Nov 17, 2022 at 03:05:14AM +0100, Jason A. Donenfeld wrote:
> On Thu, Nov 17, 2022 at 12:55:47AM +0100, Jason A. Donenfeld wrote:
> > 1) How/whether to make f(0, UR2_MAX) safe,
> >    - without additional 64-bit arithmetic,
> >    - minimizing the number of branches.
> >    I have a few ideas I'll code golf for a bit.
> > I think I can make progress with (1) alone by fiddling around with
> > godbolt enough, like usual.
> 
> The code gen is definitely worse.
> 
> Original half-open interval:
> 
>     return floor + get_random_u32_below(ceil - floor);
> 
> Suggested fully closed interval:
> 	
>     ceil = ceil - floor + 1;
>     return likely(ceil) ? floor + get_random_u32_below(ceil) : get_random_u32();

How many of these uses are going to have ceil and floor as a variable?
If they're constants (e.g. due to being in an inline function with
constant arguments) then the compiler will optimise all of the above
and the assembly code will just be either:

1. a call to get_random_u32()
2. a call to get_random_u32_below() and an addition.

If one passes ceil or floor as a variable, then yes, the code gen is
going to be as complicated as you suggest above.
Theodore Ts'o Nov. 17, 2022, 3:42 p.m. UTC | #9 
On Wed, Nov 16, 2022 at 04:47:27PM -0800, Kees Cook wrote:
> >> > - between
> >> > - ranged
> >> > - spanning
> >> > 
> >> > https://www.thefreedictionary.com/List-of-prepositions.htm
> >> > - amid
> >> > 
> >> > Sigh, names.
> >> 
> >> I think "inclusive" is best.
> >
> >I find it not very descriptive of what the function does. Is there one
> >you like second best? Or are you convinced they're all much much much
> >worse than "inclusive" that they shouldn't be considered?
> 
> Right, I don't think any are sufficiently descriptive. "Incluisve"
> with two arguments seems unambiguous and complete to me. :)

The problem with "between", "ranged", "spanning" is that they don't
tell the reader whether we're dealing with an "open interval" or a
"closed interval".  They are just different ways of saying that it's a
range between, say, 0 and 20.  But it doesn't tell you whether it
includes 0 or 20 or not.

The only way I can see for making it ambiguous is either to use the
terminology "closed interval" or "inclusive".  And "open" and "closed"
can have other meanings, so get_random_u32_inclusive() is going to be
less confusing than get_random_u32_closed().

Cheers,

					- Ted
Jason A. Donenfeld Nov. 17, 2022, 4:19 p.m. UTC | #10 
On Thu, Nov 17, 2022 at 10:42:37AM -0500, Theodore Ts'o wrote:
> On Wed, Nov 16, 2022 at 04:47:27PM -0800, Kees Cook wrote:
> > >> > - between
> > >> > - ranged
> > >> > - spanning
> > >> > 
> > >> > https://www.thefreedictionary.com/List-of-prepositions.htm
> > >> > - amid
> > >> > 
> > >> > Sigh, names.
> > >> 
> > >> I think "inclusive" is best.
> > >
> > >I find it not very descriptive of what the function does. Is there one
> > >you like second best? Or are you convinced they're all much much much
> > >worse than "inclusive" that they shouldn't be considered?
> > 
> > Right, I don't think any are sufficiently descriptive. "Incluisve"
> > with two arguments seems unambiguous and complete to me. :)
> 
> The problem with "between", "ranged", "spanning" is that they don't
> tell the reader whether we're dealing with an "open interval" or a
> "closed interval".  They are just different ways of saying that it's a
> range between, say, 0 and 20.  But it doesn't tell you whether it
> includes 0 or 20 or not.
> 
> The only way I can see for making it ambiguous is either to use the
> terminology "closed interval" or "inclusive".  And "open" and "closed"
> can have other meanings, so get_random_u32_inclusive() is going to be
> less confusing than get_random_u32_closed().

Alright, that about settles it then. I'll re-roll.

Jason
David Laight Nov. 17, 2022, 10:15 p.m. UTC | #11 
From: Theodore Ts'o
> Sent: 17 November 2022 15:43
...
> The problem with "between", "ranged", "spanning" is that they don't
> tell the reader whether we're dealing with an "open interval" or a
> "closed interval".  They are just different ways of saying that it's a
> range between, say, 0 and 20.  But it doesn't tell you whether it
> includes 0 or 20 or not.
> 
> The only way I can see for making it ambiguous is either to use the
> terminology "closed interval" or "inclusive".  And "open" and "closed"
> can have other meanings, so get_random_u32_inclusive() is going to be
> less confusing than get_random_u32_closed().

It has to be said that removing the extra function and requiring
the callers use 'base + get_random_below(high [+1] - base)' is
likely to be the only way to succinctly make the code readable
and understandable.

Otherwise readers either have to look up another function to see
what it does or waste variable brain cells on more trivia.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
diff mbox series

Patch

diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index c09ae279ef32..9f74b7d71a50 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -53,7 +53,7 @@  static unsigned long int get_module_load_offset(void)
 		 */
 		if (module_load_offset == 0)
 			module_load_offset =
-				(get_random_u32_below(1024) + 1) * PAGE_SIZE;
+				get_random_u32_between(1, 1024 + 1) * PAGE_SIZE;
 		mutex_unlock(&module_kaslr_mutex);
 	}
 	return module_load_offset;
diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index 0f722f8f779b..f31c94855a09 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -253,7 +253,7 @@  static int pkcs1pad_encrypt(struct akcipher_request *req)
 	ps_end = ctx->key_size - req->src_len - 2;
 	req_ctx->in_buf[0] = 0x02;
 	for (i = 1; i < ps_end; i++)
-		req_ctx->in_buf[i] = 1 + get_random_u32_below(255);
+		req_ctx->in_buf[i] = get_random_u32_between(1, 256);
 	req_ctx->in_buf[ps_end] = 0x00;
 
 	pkcs1pad_sg_set_buf(req_ctx->in_sg, req_ctx->in_buf,
diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index 079923d43ce2..b09b9408ec44 100644
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -962,11 +962,11 @@  static char *generate_random_sgl_divisions(struct test_sg_division *divs,
 		if (div == &divs[max_divs - 1] || get_random_u32_below(2) == 0)
 			this_len = remaining;
 		else
-			this_len = 1 + get_random_u32_below(remaining);
+			this_len = get_random_u32_between(1, remaining + 1);
 		div->proportion_of_total = this_len;
 
 		if (get_random_u32_below(4) == 0)
-			div->offset = (PAGE_SIZE - 128) + get_random_u32_below(128);
+			div->offset = get_random_u32_between(PAGE_SIZE - 128, PAGE_SIZE);
 		else if (get_random_u32_below(2) == 0)
 			div->offset = get_random_u32_below(32);
 		else
@@ -1094,12 +1094,12 @@  static void generate_random_testvec_config(struct testvec_config *cfg,
 	}
 
 	if (get_random_u32_below(2) == 0) {
-		cfg->iv_offset = 1 + get_random_u32_below(MAX_ALGAPI_ALIGNMASK);
+		cfg->iv_offset = get_random_u32_between(1, MAX_ALGAPI_ALIGNMASK + 1);
 		p += scnprintf(p, end - p, " iv_offset=%u", cfg->iv_offset);
 	}
 
 	if (get_random_u32_below(2) == 0) {
-		cfg->key_offset = 1 + get_random_u32_below(MAX_ALGAPI_ALIGNMASK);
+		cfg->key_offset = get_random_u32_between(1, MAX_ALGAPI_ALIGNMASK + 1);
 		p += scnprintf(p, end - p, " key_offset=%u", cfg->key_offset);
 	}
 
@@ -1653,7 +1653,7 @@  static void generate_random_hash_testvec(struct shash_desc *desc,
 	if (maxkeysize) {
 		vec->ksize = maxkeysize;
 		if (get_random_u32_below(4) == 0)
-			vec->ksize = 1 + get_random_u32_below(maxkeysize);
+			vec->ksize = get_random_u32_between(1, maxkeysize + 1);
 		generate_random_bytes((u8 *)vec->key, vec->ksize);
 
 		vec->setkey_error = crypto_shash_setkey(desc->tfm, vec->key,
diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
index c73621aabbd1..cfb85d00ab6e 100644
--- a/drivers/bus/mhi/host/internal.h
+++ b/drivers/bus/mhi/host/internal.h
@@ -129,7 +129,7 @@  enum mhi_pm_state {
 #define PRIMARY_CMD_RING				0
 #define MHI_DEV_WAKE_DB					127
 #define MHI_MAX_MTU					0xffff
-#define MHI_RANDOM_U32_NONZERO(bmsk)			(get_random_u32_below(bmsk) + 1)
+#define MHI_RANDOM_U32_NONZERO(bmsk)			(get_random_u32_between(1, bmsk + 1))
 
 enum mhi_er_type {
 	MHI_ER_TYPE_INVALID = 0x0,
diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
index 9fbad7317d9b..bb46b57cc230 100644
--- a/drivers/dma-buf/st-dma-fence-chain.c
+++ b/drivers/dma-buf/st-dma-fence-chain.c
@@ -400,7 +400,7 @@  static int __find_race(void *arg)
 		struct dma_fence *fence = dma_fence_get(data->fc.tail);
 		int seqno;
 
-		seqno = get_random_u32_below(data->fc.chain_length) + 1;
+		seqno = get_random_u32_between(1, data->fc.chain_length + 1);
 
 		err = dma_fence_chain_find_seqno(&fence, seqno);
 		if (err) {
diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index dd1c703b10df..b5983b19513d 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -3807,7 +3807,7 @@  static int cma_alloc_any_port(enum rdma_ucm_port_space ps,
 
 	inet_get_local_port_range(net, &low, &high);
 	remaining = (high - low) + 1;
-	rover = get_random_u32_below(remaining) + low;
+	rover = get_random_u32_between(low, remaining + low);
 retry:
 	if (last_used_port != rover) {
 		struct rdma_bind_list *bind_list;
diff --git a/drivers/infiniband/hw/hns/hns_roce_ah.c b/drivers/infiniband/hw/hns/hns_roce_ah.c
index b37d2a81584d..02481487b203 100644
--- a/drivers/infiniband/hw/hns/hns_roce_ah.c
+++ b/drivers/infiniband/hw/hns/hns_roce_ah.c
@@ -41,9 +41,8 @@  static inline u16 get_ah_udp_sport(const struct rdma_ah_attr *ah_attr)
 	u16 sport;
 
 	if (!fl)
-		sport = get_random_u32_below(IB_ROCE_UDP_ENCAP_VALID_PORT_MAX +
-					     1 - IB_ROCE_UDP_ENCAP_VALID_PORT_MIN) +
-			IB_ROCE_UDP_ENCAP_VALID_PORT_MIN;
+		sport = get_random_u32_between(IB_ROCE_UDP_ENCAP_VALID_PORT_MIN,
+					       IB_ROCE_UDP_ENCAP_VALID_PORT_MAX + 1);
 	else
 		sport = rdma_flow_label_to_udp_sport(fl);
 
diff --git a/drivers/mtd/nand/raw/nandsim.c b/drivers/mtd/nand/raw/nandsim.c
index 274a31b93100..d4d7c6dac001 100644
--- a/drivers/mtd/nand/raw/nandsim.c
+++ b/drivers/mtd/nand/raw/nandsim.c
@@ -1405,7 +1405,7 @@  static void ns_do_bit_flips(struct nandsim *ns, int num)
 	if (bitflips && get_random_u16() < (1 << 6)) {
 		int flips = 1;
 		if (bitflips > 1)
-			flips = get_random_u32_below(bitflips) + 1;
+			flips = get_random_u32_between(1, bitflips + 1);
 		while (flips--) {
 			int pos = get_random_u32_below(num * 8);
 			ns->buf.byte[pos / 8] ^= (1 << (pos % 8));
diff --git a/drivers/net/wireguard/selftest/allowedips.c b/drivers/net/wireguard/selftest/allowedips.c
index 78a916f30c82..34d5981f4513 100644
--- a/drivers/net/wireguard/selftest/allowedips.c
+++ b/drivers/net/wireguard/selftest/allowedips.c
@@ -285,7 +285,7 @@  static __init bool randomized_test(void)
 
 	for (i = 0; i < NUM_RAND_ROUTES; ++i) {
 		get_random_bytes(ip, 4);
-		cidr = get_random_u32_below(32) + 1;
+		cidr = get_random_u32_between(1, 32 + 1);
 		peer = peers[get_random_u32_below(NUM_PEERS)];
 		if (wg_allowedips_insert_v4(&t, (struct in_addr *)ip, cidr,
 					    peer, &mutex) < 0) {
@@ -311,7 +311,7 @@  static __init bool randomized_test(void)
 				mutated[k] = (mutated[k] & mutate_mask[k]) |
 					     (~mutate_mask[k] &
 					      get_random_u8());
-			cidr = get_random_u32_below(32) + 1;
+			cidr = get_random_u32_between(1, 32 + 1);
 			peer = peers[get_random_u32_below(NUM_PEERS)];
 			if (wg_allowedips_insert_v4(&t,
 						    (struct in_addr *)mutated,
@@ -329,7 +329,7 @@  static __init bool randomized_test(void)
 
 	for (i = 0; i < NUM_RAND_ROUTES; ++i) {
 		get_random_bytes(ip, 16);
-		cidr = get_random_u32_below(128) + 1;
+		cidr = get_random_u32_between(1, 128 + 1);
 		peer = peers[get_random_u32_below(NUM_PEERS)];
 		if (wg_allowedips_insert_v6(&t, (struct in6_addr *)ip, cidr,
 					    peer, &mutex) < 0) {
@@ -355,7 +355,7 @@  static __init bool randomized_test(void)
 				mutated[k] = (mutated[k] & mutate_mask[k]) |
 					     (~mutate_mask[k] &
 					      get_random_u8());
-			cidr = get_random_u32_below(128) + 1;
+			cidr = get_random_u32_between(1, 128 + 1);
 			peer = peers[get_random_u32_below(NUM_PEERS)];
 			if (wg_allowedips_insert_v6(&t,
 						    (struct in6_addr *)mutated,
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
index 23c971b77965..0e6bf5e5c8a9 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
@@ -1128,7 +1128,7 @@  static void brcmf_p2p_afx_handler(struct work_struct *work)
 	if (afx_hdl->is_listen && afx_hdl->my_listen_chan)
 		/* 100ms ~ 300ms */
 		err = brcmf_p2p_discover_listen(p2p, afx_hdl->my_listen_chan,
-						100 * (1 + get_random_u32_below(3)));
+						100 * get_random_u32_between(1, 4));
 	else
 		err = brcmf_p2p_act_frm_search(p2p, afx_hdl->peer_listen_chan);
 
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c b/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c
index 1696fbf1009a..f0b94633834e 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c
@@ -1099,7 +1099,7 @@  static void iwl_mvm_mac_ctxt_cmd_fill_ap(struct iwl_mvm *mvm,
 			iwl_mvm_mac_ap_iterator, &data);
 
 		if (data.beacon_device_ts) {
-			u32 rand = get_random_u32_below(64 - 36) + 36;
+			u32 rand = get_random_u32_between(36, 64);
 			mvmvif->ap_beacon_time = data.beacon_device_ts +
 				ieee80211_tu_to_usec(data.beacon_int * rand /
 						     100);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 334415d946f8..8319fdc59fb4 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2588,7 +2588,7 @@  static void new_curseg(struct f2fs_sb_info *sbi, int type, bool new_sec)
 	curseg->alloc_type = LFS;
 	if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_BLK)
 		curseg->fragment_remained_chunk =
-				get_random_u32_below(sbi->max_fragment_chunk) + 1;
+				get_random_u32_between(1, sbi->max_fragment_chunk + 1);
 }
 
 static int __next_free_blkoff(struct f2fs_sb_info *sbi,
@@ -2625,9 +2625,9 @@  static void __refresh_next_blkoff(struct f2fs_sb_info *sbi,
 			/* To allocate block chunks in different sizes, use random number */
 			if (--seg->fragment_remained_chunk <= 0) {
 				seg->fragment_remained_chunk =
-				   get_random_u32_below(sbi->max_fragment_chunk) + 1;
+				   get_random_u32_between(1, sbi->max_fragment_chunk + 1);
 				seg->next_blkoff +=
-				   get_random_u32_below(sbi->max_fragment_hole) + 1;
+				   get_random_u32_between(1, sbi->max_fragment_hole + 1);
 			}
 		}
 	}
diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c
index 7b619f16a492..eed30ad29796 100644
--- a/kernel/kcsan/selftest.c
+++ b/kernel/kcsan/selftest.c
@@ -31,7 +31,7 @@  static bool __init test_encode_decode(void)
 	int i;
 
 	for (i = 0; i < ITERS_PER_TEST; ++i) {
-		size_t size = get_random_u32_below(MAX_ENCODABLE_SIZE) + 1;
+		size_t size = get_random_u32_between(1, MAX_ENCODABLE_SIZE + 1);
 		bool is_write = !!get_random_u32_below(2);
 		unsigned long verif_masked_addr;
 		long encoded_watchpoint;
diff --git a/lib/test_hexdump.c b/lib/test_hexdump.c
index efc50fd30a44..f4ff3041ec10 100644
--- a/lib/test_hexdump.c
+++ b/lib/test_hexdump.c
@@ -149,7 +149,7 @@  static void __init test_hexdump(size_t len, int rowsize, int groupsize,
 static void __init test_hexdump_set(int rowsize, bool ascii)
 {
 	size_t d = min_t(size_t, sizeof(data_b), rowsize);
-	size_t len = get_random_u32_below(d) + 1;
+	size_t len = get_random_u32_between(1, d + 1);
 
 	test_hexdump(len, rowsize, 4, ascii);
 	test_hexdump(len, rowsize, 2, ascii);
@@ -208,11 +208,11 @@  static void __init test_hexdump_overflow(size_t buflen, size_t len,
 static void __init test_hexdump_overflow_set(size_t buflen, bool ascii)
 {
 	unsigned int i = 0;
-	int rs = (get_random_u32_below(2) + 1) * 16;
+	int rs = get_random_u32_between(1, 3) * 16;
 
 	do {
 		int gs = 1 << i;
-		size_t len = get_random_u32_below(rs) + gs;
+		size_t len = get_random_u32_between(gs, rs + gs);
 
 		test_hexdump_overflow(buflen, rounddown(len, gs), rs, gs, ascii);
 	} while (i++ < 3);
@@ -223,11 +223,11 @@  static int __init test_hexdump_init(void)
 	unsigned int i;
 	int rowsize;
 
-	rowsize = (get_random_u32_below(2) + 1) * 16;
+	rowsize = get_random_u32_between(1, 3) * 16;
 	for (i = 0; i < 16; i++)
 		test_hexdump_set(rowsize, false);
 
-	rowsize = (get_random_u32_below(2) + 1) * 16;
+	rowsize = get_random_u32_between(1, 3) * 16;
 	for (i = 0; i < 16; i++)
 		test_hexdump_set(rowsize, true);
 
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 6d10187eddac..da5efc8b8543 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -126,7 +126,7 @@  __test(const char *expect, int elen, const char *fmt, ...)
 	 * be able to print it as expected.
 	 */
 	failed_tests += do_test(BUF_SIZE, expect, elen, fmt, ap);
-	rand = 1 + get_random_u32_below(elen + 1);
+	rand = get_random_u32_between(1, elen + 2);
 	/* Since elen < BUF_SIZE, we have 1 <= rand <= BUF_SIZE. */
 	failed_tests += do_test(rand, expect, elen, fmt, ap);
 	failed_tests += do_test(0, expect, elen, fmt, ap);
diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
index 104f09ea5fcc..7a2caf4596c5 100644
--- a/lib/test_vmalloc.c
+++ b/lib/test_vmalloc.c
@@ -151,7 +151,7 @@  static int random_size_alloc_test(void)
 	int i;
 
 	for (i = 0; i < test_loop_count; i++) {
-		n = get_random_u32_below(100) + 1;
+		n = get_random_u32_between(1, 101);
 		p = vmalloc(n * PAGE_SIZE);
 
 		if (!p)
@@ -291,12 +291,12 @@  pcpu_alloc_test(void)
 		return -1;
 
 	for (i = 0; i < 35000; i++) {
-		size = get_random_u32_below(PAGE_SIZE / 4) + 1;
+		size = get_random_u32_between(1, PAGE_SIZE / 4 + 1);
 
 		/*
 		 * Maximum PAGE_SIZE
 		 */
-		align = 1 << (get_random_u32_below(11) + 1);
+		align = 1 << get_random_u32_between(1, 12);
 
 		pcpu[i] = __alloc_percpu(size, align);
 		if (!pcpu[i])
diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 640f9c7f8e44..6167e19056f0 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_between(1, 1024 + 1);
 		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_between(1, 5);
 		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_between(1, 1024 + 1);
 		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..99abe86fc9b1 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_between(8, 308),
 						     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..08f0152c32da 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_between(si->lowest_bit, si->highest_bit + 1);
 		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_between(1, p->highest_bit + 1);
 		}
 		nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
 
diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index b2f9679066c4..bab37a529db5 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -7373,9 +7373,8 @@  static int get_conn_info(struct sock *sk, struct hci_dev *hdev, void *data,
 	/* To avoid client trying to guess when to poll again for information we
 	 * calculate conn info age as random value between min/max set in hdev.
 	 */
-	conn_info_age = hdev->conn_info_min_age +
-			get_random_u32_below(hdev->conn_info_max_age -
-					     hdev->conn_info_min_age);
+	conn_info_age = get_random_u32_between(hdev->conn_info_min_age,
+					       hdev->conn_info_max_age);
 
 	/* Query controller to refresh cached values if they are too old or were
 	 * never read.
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 95da2ddc1c20..5eb401003368 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2380,9 +2380,8 @@  static void set_cur_queue_map(struct pktgen_dev *pkt_dev)
 	else if (pkt_dev->queue_map_min <= pkt_dev->queue_map_max) {
 		__u16 t;
 		if (pkt_dev->flags & F_QUEUE_MAP_RND) {
-			t = get_random_u32_below(pkt_dev->queue_map_max -
-						 pkt_dev->queue_map_min + 1) +
-			    pkt_dev->queue_map_min;
+			t = get_random_u32_between(pkt_dev->queue_map_min,
+						   pkt_dev->queue_map_max + 1);
 		} else {
 			t = pkt_dev->cur_queue_map + 1;
 			if (t > pkt_dev->queue_map_max)
@@ -2478,9 +2477,8 @@  static void mod_cur_headers(struct pktgen_dev *pkt_dev)
 
 	if (pkt_dev->udp_src_min < pkt_dev->udp_src_max) {
 		if (pkt_dev->flags & F_UDPSRC_RND)
-			pkt_dev->cur_udp_src = get_random_u32_below(
-				pkt_dev->udp_src_max - pkt_dev->udp_src_min) +
-				pkt_dev->udp_src_min;
+			pkt_dev->cur_udp_src = get_random_u32_between(pkt_dev->udp_src_min,
+								      pkt_dev->udp_src_max);
 
 		else {
 			pkt_dev->cur_udp_src++;
@@ -2491,9 +2489,8 @@  static void mod_cur_headers(struct pktgen_dev *pkt_dev)
 
 	if (pkt_dev->udp_dst_min < pkt_dev->udp_dst_max) {
 		if (pkt_dev->flags & F_UDPDST_RND) {
-			pkt_dev->cur_udp_dst = get_random_u32_below(
-				pkt_dev->udp_dst_max - pkt_dev->udp_dst_min) +
-				pkt_dev->udp_dst_min;
+			pkt_dev->cur_udp_dst = get_random_u32_between(pkt_dev->udp_dst_min,
+								      pkt_dev->udp_dst_max);
 		} else {
 			pkt_dev->cur_udp_dst++;
 			if (pkt_dev->cur_udp_dst >= pkt_dev->udp_dst_max)
@@ -2508,7 +2505,7 @@  static void mod_cur_headers(struct pktgen_dev *pkt_dev)
 		if (imn < imx) {
 			__u32 t;
 			if (pkt_dev->flags & F_IPSRC_RND)
-				t = get_random_u32_below(imx - imn) + imn;
+				t = get_random_u32_between(imn, imx);
 			else {
 				t = ntohl(pkt_dev->cur_saddr);
 				t++;
@@ -2530,8 +2527,7 @@  static void mod_cur_headers(struct pktgen_dev *pkt_dev)
 				if (pkt_dev->flags & F_IPDST_RND) {
 
 					do {
-						t = get_random_u32_below(imx - imn) +
-						    imn;
+						t = get_random_u32_between(imn, imx);
 						s = htonl(t);
 					} while (ipv4_is_loopback(s) ||
 						ipv4_is_multicast(s) ||
@@ -2578,9 +2574,8 @@  static void mod_cur_headers(struct pktgen_dev *pkt_dev)
 	if (pkt_dev->min_pkt_size < pkt_dev->max_pkt_size) {
 		__u32 t;
 		if (pkt_dev->flags & F_TXSIZE_RND) {
-			t = get_random_u32_below(pkt_dev->max_pkt_size -
-						 pkt_dev->min_pkt_size) +
-			    pkt_dev->min_pkt_size;
+			t = get_random_u32_between(pkt_dev->min_pkt_size,
+						   pkt_dev->max_pkt_size);
 		} else {
 			t = pkt_dev->cur_pkt_size + 1;
 			if (t > pkt_dev->max_pkt_size)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3b076e5ba932..1a348298a99e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3647,7 +3647,7 @@  static void tcp_send_challenge_ack(struct sock *sk)
 
 		WRITE_ONCE(net->ipv4.tcp_challenge_timestamp, now);
 		WRITE_ONCE(net->ipv4.tcp_challenge_count,
-			   half + get_random_u32_below(ack_limit));
+			   get_random_u32_between(half, ack_limit + half));
 	}
 	count = READ_ONCE(net->ipv4.tcp_challenge_count);
 	if (count > 0) {
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index daf89a2eb492..3f750e6d0ac3 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -104,7 +104,7 @@  static inline u32 cstamp_delta(unsigned long cstamp)
 static inline s32 rfc3315_s14_backoff_init(s32 irt)
 {
 	/* multiply 'initial retransmission time' by 0.9 .. 1.1 */
-	u64 tmp = (900000 + get_random_u32_below(200001)) * (u64)irt;
+	u64 tmp = get_random_u32_between(900000, 1100001) * (u64)irt;
 	do_div(tmp, 1000000);
 	return (s32)tmp;
 }
@@ -112,11 +112,11 @@  static inline s32 rfc3315_s14_backoff_init(s32 irt)
 static inline s32 rfc3315_s14_backoff_update(s32 rt, s32 mrt)
 {
 	/* multiply 'retransmission timeout' by 1.9 .. 2.1 */
-	u64 tmp = (1900000 + get_random_u32_below(200001)) * (u64)rt;
+	u64 tmp = get_random_u32_between(1900000, 2100001) * (u64)rt;
 	do_div(tmp, 1000000);
 	if ((s32)tmp > mrt) {
 		/* multiply 'maximum retransmission time' by 0.9 .. 1.1 */
-		tmp = (900000 + get_random_u32_below(200001)) * (u64)mrt;
+		tmp = get_random_u32_between(900000, 1100001) * (u64)mrt;
 		do_div(tmp, 1000000);
 	}
 	return (s32)tmp;
diff --git a/net/netfilter/nf_nat_helper.c b/net/netfilter/nf_nat_helper.c
index bf591e6af005..a12c3470f7fd 100644
--- a/net/netfilter/nf_nat_helper.c
+++ b/net/netfilter/nf_nat_helper.c
@@ -223,7 +223,7 @@  u16 nf_nat_exp_find_port(struct nf_conntrack_expect *exp, u16 port)
 		if (res != -EBUSY || (--attempts_left < 0))
 			break;
 
-		port = min + get_random_u32_below(range);
+		port = get_random_u32_between(min, range + min);
 	}
 
 	return 0;
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 40f831854774..c118476f73ae 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -2072,7 +2072,7 @@  int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high)
 	} else {
 		u32 spi = 0;
 		for (h = 0; h < high-low+1; h++) {
-			spi = low + get_random_u32_below(high - low + 1);
+			spi = get_random_u32_between(low, high + 1);
 			x0 = xfrm_state_lookup(net, mark, &x->id.daddr, htonl(spi), x->id.proto, x->props.family);
 			if (x0 == NULL) {
 				newspi = htonl(spi);