treewide: use prandom_u32_max() when possible, part 1

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 mechanically with this coccinelle script:

@basic@
expression E;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u64;
@@
(
- ((T)get_random_u32() % (E))
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ((E) - 1))
+ prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2)
|
- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ~PAGE_MASK)
+ prandom_u32_max(PAGE_SIZE)
)

@multi_line@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
identifier RAND;
expression E;
@@

-       RAND = get_random_u32();
        ... when != RAND
-       RAND %= (E);
+       RAND = prandom_u32_max(E);

// Find a potential literal
@literal_mask@
expression LITERAL;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
position p;
@@

        ((T)get_random_u32()@p & (LITERAL))

// Add one to the literal.
@script:python add_one@
literal << literal_mask.LITERAL;
RESULT;
@@

value = None
if literal.startswith('0x'):
        value = int(literal, 16)
elif literal[0] in '123456789':
        value = int(literal, 10)
if value is None:
        print("I don't know how to handle %s" % (literal))
        cocci.include_match(False)
elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1:
        print("Skipping 0x%x for cleanup elsewhere" % (value))
        cocci.include_match(False)
elif value & (value + 1) != 0:
        print("Skipping 0x%x because it's not a power of two minus one" % (value))
        cocci.include_match(False)
elif literal.startswith('0x'):
        coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1))
else:
        coccinelle.RESULT = cocci.make_expr("%d" % (value + 1))

// Replace the literal mask with the calculated result.
@plus_one@
expression literal_mask.LITERAL;
position literal_mask.p;
expression add_one.RESULT;
identifier FUNC;
@@

-       (FUNC()@p & (LITERAL))
+       prandom_u32_max(RESULT)

@collapse_ret@
type T;
identifier VAR;
expression E;
@@

 {
-       T VAR;
-       VAR = (E);
-       return VAR;
+       return E;
 }

@drop_var@
type T;
identifier VAR;
@@

 {
-       T VAR;
        ... when != VAR
 }

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: KP Singh <kpsingh@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc
Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

arch/arm/kernel/process.c

@@ -375,7 +375,7 @@ static unsigned long sigpage_addr(const struct mm_struct *mm,
 
 	slots = ((last - first) >> PAGE_SHIFT) + 1;
 
-	offset = get_random_int() % slots;
+	offset = prandom_u32_max(slots);
 
 	addr = first + (offset << PAGE_SHIFT);
 

arch/arm64/kernel/process.c

@@ -595,7 +595,7 @@ unsigned long __get_wchan(struct task_struct *p)
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() & ~PAGE_MASK;
+		sp -= prandom_u32_max(PAGE_SIZE);
 	return sp & ~0xf;
 }
 

arch/loongarch/kernel/process.c

@@ -293,7 +293,7 @@ unsigned long stack_top(void)
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() & ~PAGE_MASK;
+		sp -= prandom_u32_max(PAGE_SIZE);
 
 	return sp & STACK_ALIGN;
 }

arch/loongarch/kernel/vdso.c

@@ -78,7 +78,7 @@ static unsigned long vdso_base(void)
 	unsigned long base = STACK_TOP;
 
 	if (current->flags & PF_RANDOMIZE) {
-		base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
+		base += prandom_u32_max(VDSO_RANDOMIZE_SIZE);
 		base = PAGE_ALIGN(base);
 	}
 

arch/mips/kernel/process.c

@@ -711,7 +711,7 @@ unsigned long mips_stack_top(void)
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() & ~PAGE_MASK;
+		sp -= prandom_u32_max(PAGE_SIZE);
 
 	return sp & ALMASK;
 }

arch/mips/kernel/vdso.c

@@ -79,7 +79,7 @@ static unsigned long vdso_base(void)
 	}
 
 	if (current->flags & PF_RANDOMIZE) {
-		base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
+		base += prandom_u32_max(VDSO_RANDOMIZE_SIZE);
 		base = PAGE_ALIGN(base);
 	}
 

arch/parisc/kernel/vdso.c

@@ -75,7 +75,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
 
 	map_base = mm->mmap_base;
 	if (current->flags & PF_RANDOMIZE)
-		map_base -= (get_random_int() & 0x1f) * PAGE_SIZE;
+		map_base -= prandom_u32_max(0x20) * PAGE_SIZE;
 
 	vdso_text_start = get_unmapped_area(NULL, map_base, vdso_text_len, 0, 0);
 

arch/powerpc/kernel/process.c

@@ -2308,6 +2308,6 @@ void notrace __ppc64_runlatch_off(void)
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() & ~PAGE_MASK;
+		sp -= prandom_u32_max(PAGE_SIZE);
 	return sp & ~0xf;
 }

arch/s390/kernel/process.c

@@ -224,7 +224,7 @@ unsigned long __get_wchan(struct task_struct *p)
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() & ~PAGE_MASK;
+		sp -= prandom_u32_max(PAGE_SIZE);
 	return sp & ~0xf;
 }
 

arch/s390/kernel/vdso.c

@@ -227,7 +227,7 @@ static unsigned long vdso_addr(unsigned long start, unsigned long len)
 	end -= len;
 
 	if (end > start) {
-		offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
+		offset = prandom_u32_max(((end - start) >> PAGE_SHIFT) + 1);
 		addr = start + (offset << PAGE_SHIFT);
 	} else {
 		addr = start;

arch/sparc/vdso/vma.c

@@ -354,7 +354,7 @@ static unsigned long vdso_addr(unsigned long start, unsigned int len)
 	unsigned int offset;
 
 	/* This loses some more bits than a modulo, but is cheaper */
-	offset = get_random_int() & (PTRS_PER_PTE - 1);
+	offset = prandom_u32_max(PTRS_PER_PTE);
 	return start + (offset << PAGE_SHIFT);
 }
 

arch/um/kernel/process.c

@@ -356,7 +356,7 @@ int singlestepping(void * t)
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() % 8192;
+		sp -= prandom_u32_max(8192);
 	return sp & ~0xf;
 }
 #endif

arch/x86/entry/vdso/vma.c

@@ -327,7 +327,7 @@ static unsigned long vdso_addr(unsigned long start, unsigned len)
 	end -= len;
 
 	if (end > start) {
-		offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
+		offset = prandom_u32_max(((end - start) >> PAGE_SHIFT) + 1);
 		addr = start + (offset << PAGE_SHIFT);
 	} else {
 		addr = start;

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_int() % 1024 + 1) * PAGE_SIZE;
+				(prandom_u32_max(1024) + 1) * PAGE_SIZE;
 		mutex_unlock(&module_kaslr_mutex);
 	}
 	return module_load_offset;

arch/x86/kernel/process.c

@@ -965,7 +965,7 @@ early_param("idle", idle_setup);
 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
-		sp -= get_random_int() % 8192;
+		sp -= prandom_u32_max(8192);
 	return sp & ~0xf;
 }
 

arch/x86/mm/pat/cpa-test.c

@@ -136,10 +136,10 @@ static int pageattr_test(void)
 	failed += print_split(&sa);
 
 	for (i = 0; i < NTEST; i++) {
-		unsigned long pfn = prandom_u32() % max_pfn_mapped;
+		unsigned long pfn = prandom_u32_max(max_pfn_mapped);
 
 		addr[i] = (unsigned long)__va(pfn << PAGE_SHIFT);
-		len[i] = prandom_u32() % NPAGES;
+		len[i] = prandom_u32_max(NPAGES);
 		len[i] = min_t(unsigned long, len[i], max_pfn_mapped - pfn - 1);
 
 		if (len[i] == 0)

crypto/testmgr.c

@@ -855,9 +855,9 @@ static int prepare_keybuf(const u8 *key, unsigned int ksize,
 /* Generate a random length in range [0, max_len], but prefer smaller values */
 static unsigned int generate_random_length(unsigned int max_len)
 {
-	unsigned int len = prandom_u32() % (max_len + 1);
+	unsigned int len = prandom_u32_max(max_len + 1);
 
-	switch (prandom_u32() % 4) {
+	switch (prandom_u32_max(4)) {
 	case 0:
 		return len % 64;
 	case 1:
@@ -874,14 +874,14 @@ static void flip_random_bit(u8 *buf, size_t size)
 {
 	size_t bitpos;
 
-	bitpos = prandom_u32() % (size * 8);
+	bitpos = prandom_u32_max(size * 8);
 	buf[bitpos / 8] ^= 1 << (bitpos % 8);
 }
 
 /* Flip a random byte in the given nonempty data buffer */
 static void flip_random_byte(u8 *buf, size_t size)
 {
-	buf[prandom_u32() % size] ^= 0xff;
+	buf[prandom_u32_max(size)] ^= 0xff;
 }
 
 /* Sometimes make some random changes to the given nonempty data buffer */
@@ -891,15 +891,15 @@ static void mutate_buffer(u8 *buf, size_t size)
 	size_t i;
 
 	/* Sometimes flip some bits */
-	if (prandom_u32() % 4 == 0) {
-		num_flips = min_t(size_t, 1 << (prandom_u32() % 8), size * 8);
+	if (prandom_u32_max(4) == 0) {
+		num_flips = min_t(size_t, 1 << prandom_u32_max(8), size * 8);
 		for (i = 0; i < num_flips; i++)
 			flip_random_bit(buf, size);
 	}
 
 	/* Sometimes flip some bytes */
-	if (prandom_u32() % 4 == 0) {
-		num_flips = min_t(size_t, 1 << (prandom_u32() % 8), size);
+	if (prandom_u32_max(4) == 0) {
+		num_flips = min_t(size_t, 1 << prandom_u32_max(8), size);
 		for (i = 0; i < num_flips; i++)
 			flip_random_byte(buf, size);
 	}
@@ -915,11 +915,11 @@ static void generate_random_bytes(u8 *buf, size_t count)
 	if (count == 0)
 		return;
 
-	switch (prandom_u32() % 8) { /* Choose a generation strategy */
+	switch (prandom_u32_max(8)) { /* Choose a generation strategy */
 	case 0:
 	case 1:
 		/* All the same byte, plus optional mutations */
-		switch (prandom_u32() % 4) {
+		switch (prandom_u32_max(4)) {
 		case 0:
 			b = 0x00;
 			break;
@@ -959,24 +959,24 @@ static char *generate_random_sgl_divisions(struct test_sg_division *divs,
 		unsigned int this_len;
 		const char *flushtype_str;
 
-		if (div == &divs[max_divs - 1] || prandom_u32() % 2 == 0)
+		if (div == &divs[max_divs - 1] || prandom_u32_max(2) == 0)
 			this_len = remaining;
 		else
-			this_len = 1 + (prandom_u32() % remaining);
+			this_len = 1 + prandom_u32_max(remaining);
 		div->proportion_of_total = this_len;
 
-		if (prandom_u32() % 4 == 0)
-			div->offset = (PAGE_SIZE - 128) + (prandom_u32() % 128);
-		else if (prandom_u32() % 2 == 0)
-			div->offset = prandom_u32() % 32;
+		if (prandom_u32_max(4) == 0)
+			div->offset = (PAGE_SIZE - 128) + prandom_u32_max(128);
+		else if (prandom_u32_max(2) == 0)
+			div->offset = prandom_u32_max(32);
 		else
-			div->offset = prandom_u32() % PAGE_SIZE;
-		if (prandom_u32() % 8 == 0)
+			div->offset = prandom_u32_max(PAGE_SIZE);
+		if (prandom_u32_max(8) == 0)
 			div->offset_relative_to_alignmask = true;
 
 		div->flush_type = FLUSH_TYPE_NONE;
 		if (gen_flushes) {
-			switch (prandom_u32() % 4) {
+			switch (prandom_u32_max(4)) {
 			case 0:
 				div->flush_type = FLUSH_TYPE_REIMPORT;
 				break;
@@ -988,7 +988,7 @@ static char *generate_random_sgl_divisions(struct test_sg_division *divs,
 
 		if (div->flush_type != FLUSH_TYPE_NONE &&
 		    !(req_flags & CRYPTO_TFM_REQ_MAY_SLEEP) &&
-		    prandom_u32() % 2 == 0)
+		    prandom_u32_max(2) == 0)
 			div->nosimd = true;
 
 		switch (div->flush_type) {
@@ -1035,7 +1035,7 @@ static void generate_random_testvec_config(struct testvec_config *cfg,
 
 	p += scnprintf(p, end - p, "random:");
 
-	switch (prandom_u32() % 4) {
+	switch (prandom_u32_max(4)) {
 	case 0:
 	case 1:
 		cfg->inplace_mode = OUT_OF_PLACE;
@@ -1050,12 +1050,12 @@ static void generate_random_testvec_config(struct testvec_config *cfg,
 		break;
 	}
 
-	if (prandom_u32() % 2 == 0) {
+	if (prandom_u32_max(2) == 0) {
 		cfg->req_flags |= CRYPTO_TFM_REQ_MAY_SLEEP;
 		p += scnprintf(p, end - p, " may_sleep");
 	}
 
-	switch (prandom_u32() % 4) {
+	switch (prandom_u32_max(4)) {
 	case 0:
 		cfg->finalization_type = FINALIZATION_TYPE_FINAL;
 		p += scnprintf(p, end - p, " use_final");
@@ -1071,7 +1071,7 @@ static void generate_random_testvec_config(struct testvec_config *cfg,
 	}
 
 	if (!(cfg->req_flags & CRYPTO_TFM_REQ_MAY_SLEEP) &&
-	    prandom_u32() % 2 == 0) {
+	    prandom_u32_max(2) == 0) {
 		cfg->nosimd = true;
 		p += scnprintf(p, end - p, " nosimd");
 	}
@@ -1084,7 +1084,7 @@ static void generate_random_testvec_config(struct testvec_config *cfg,
 					  cfg->req_flags);
 	p += scnprintf(p, end - p, "]");
 
-	if (cfg->inplace_mode == OUT_OF_PLACE && prandom_u32() % 2 == 0) {
+	if (cfg->inplace_mode == OUT_OF_PLACE && prandom_u32_max(2) == 0) {
 		p += scnprintf(p, end - p, " dst_divs=[");
 		p = generate_random_sgl_divisions(cfg->dst_divs,
 						  ARRAY_SIZE(cfg->dst_divs),
@@ -1093,13 +1093,13 @@ static void generate_random_testvec_config(struct testvec_config *cfg,
 		p += scnprintf(p, end - p, "]");
 	}
 
-	if (prandom_u32() % 2 == 0) {
-		cfg->iv_offset = 1 + (prandom_u32() % MAX_ALGAPI_ALIGNMASK);
+	if (prandom_u32_max(2) == 0) {
+		cfg->iv_offset = 1 + prandom_u32_max(MAX_ALGAPI_ALIGNMASK);
 		p += scnprintf(p, end - p, " iv_offset=%u", cfg->iv_offset);
 	}
 
-	if (prandom_u32() % 2 == 0) {
-		cfg->key_offset = 1 + (prandom_u32() % MAX_ALGAPI_ALIGNMASK);
+	if (prandom_u32_max(2) == 0) {
+		cfg->key_offset = 1 + prandom_u32_max(MAX_ALGAPI_ALIGNMASK);
 		p += scnprintf(p, end - p, " key_offset=%u", cfg->key_offset);
 	}
 
@@ -1652,8 +1652,8 @@ static void generate_random_hash_testvec(struct shash_desc *desc,
 	vec->ksize = 0;
 	if (maxkeysize) {
 		vec->ksize = maxkeysize;
-		if (prandom_u32() % 4 == 0)
-			vec->ksize = 1 + (prandom_u32() % maxkeysize);
+		if (prandom_u32_max(4) == 0)
+			vec->ksize = 1 + prandom_u32_max(maxkeysize);
 		generate_random_bytes((u8 *)vec->key, vec->ksize);
 
 		vec->setkey_error = crypto_shash_setkey(desc->tfm, vec->key,
@@ -2218,13 +2218,13 @@ static void mutate_aead_message(struct aead_testvec *vec, bool aad_iv,
 	const unsigned int aad_tail_size = aad_iv ? ivsize : 0;
 	const unsigned int authsize = vec->clen - vec->plen;
 
-	if (prandom_u32() % 2 == 0 && vec->alen > aad_tail_size) {
+	if (prandom_u32_max(2) == 0 && vec->alen > aad_tail_size) {
 		 /* Mutate the AAD */
 		flip_random_bit((u8 *)vec->assoc, vec->alen - aad_tail_size);
-		if (prandom_u32() % 2 == 0)
+		if (prandom_u32_max(2) == 0)
 			return;
 	}
-	if (prandom_u32() % 2 == 0) {
+	if (prandom_u32_max(2) == 0) {
 		/* Mutate auth tag (assuming it's at the end of ciphertext) */
 		flip_random_bit((u8 *)vec->ctext + vec->plen, authsize);
 	} else {
@@ -2249,7 +2249,7 @@ static void generate_aead_message(struct aead_request *req,
 	const unsigned int ivsize = crypto_aead_ivsize(tfm);
 	const unsigned int authsize = vec->clen - vec->plen;
 	const bool inauthentic = (authsize >= MIN_COLLISION_FREE_AUTHSIZE) &&
-				 (prefer_inauthentic || prandom_u32() % 4 == 0);
+				 (prefer_inauthentic || prandom_u32_max(4) == 0);
 
 	/* Generate the AAD. */
 	generate_random_bytes((u8 *)vec->assoc, vec->alen);
@@ -2257,7 +2257,7 @@ static void generate_aead_message(struct aead_request *req,
 		/* Avoid implementation-defined behavior. */
 		memcpy((u8 *)vec->assoc + vec->alen - ivsize, vec->iv, ivsize);
 
-	if (inauthentic && prandom_u32() % 2 == 0) {
+	if (inauthentic && prandom_u32_max(2) == 0) {
 		/* Generate a random ciphertext. */
 		generate_random_bytes((u8 *)vec->ctext, vec->clen);
 	} else {
@@ -2321,8 +2321,8 @@ static void generate_random_aead_testvec(struct aead_request *req,
 
 	/* Key: length in [0, maxkeysize], but usually choose maxkeysize */
 	vec->klen = maxkeysize;
-	if (prandom_u32() % 4 == 0)
-		vec->klen = prandom_u32() % (maxkeysize + 1);
+	if (prandom_u32_max(4) == 0)
+		vec->klen = prandom_u32_max(maxkeysize + 1);
 	generate_random_bytes((u8 *)vec->key, vec->klen);
 	vec->setkey_error = crypto_aead_setkey(tfm, vec->key, vec->klen);
 
@@ -2331,8 +2331,8 @@ static void generate_random_aead_testvec(struct aead_request *req,
 
 	/* Tag length: in [0, maxauthsize], but usually choose maxauthsize */
 	authsize = maxauthsize;
-	if (prandom_u32() % 4 == 0)
-		authsize = prandom_u32() % (maxauthsize + 1);
+	if (prandom_u32_max(4) == 0)
+		authsize = prandom_u32_max(maxauthsize + 1);
 	if (prefer_inauthentic && authsize < MIN_COLLISION_FREE_AUTHSIZE)
 		authsize = MIN_COLLISION_FREE_AUTHSIZE;
 	if (WARN_ON(authsize > maxdatasize))
@@ -2342,7 +2342,7 @@ static void generate_random_aead_testvec(struct aead_request *req,
 
 	/* AAD, plaintext, and ciphertext lengths */
 	total_len = generate_random_length(maxdatasize);
-	if (prandom_u32() % 4 == 0)
+	if (prandom_u32_max(4) == 0)
 		vec->alen = 0;
 	else
 		vec->alen = generate_random_length(total_len);
@@ -2958,8 +2958,8 @@ static void generate_random_cipher_testvec(struct skcipher_request *req,
 
 	/* Key: length in [0, maxkeysize], but usually choose maxkeysize */
 	vec->klen = maxkeysize;
-	if (prandom_u32() % 4 == 0)
-		vec->klen = prandom_u32() % (maxkeysize + 1);
+	if (prandom_u32_max(4) == 0)
+		vec->klen = prandom_u32_max(maxkeysize + 1);
 	generate_random_bytes((u8 *)vec->key, vec->klen);
 	vec->setkey_error = crypto_skcipher_setkey(tfm, vec->key, vec->klen);
 

drivers/block/drbd/drbd_receiver.c

@@ -781,7 +781,7 @@ static struct socket *drbd_wait_for_connect(struct drbd_connection *connection,
 
 	timeo = connect_int * HZ;
 	/* 28.5% random jitter */
-	timeo += (prandom_u32() & 1) ? timeo / 7 : -timeo / 7;
+	timeo += prandom_u32_max(2) ? timeo / 7 : -timeo / 7;
 
 	err = wait_for_completion_interruptible_timeout(&ad->door_bell, timeo);
 	if (err <= 0)
@@ -1004,7 +1004,7 @@ retry:
 				drbd_warn(connection, "Error receiving initial packet\n");
 				sock_release(s);
 randomize:
-				if (prandom_u32() & 1)
+				if (prandom_u32_max(2))
 					goto retry;
 			}
 		}

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -2424,7 +2424,7 @@ gen8_dispatch_bsd_engine(struct drm_i915_private *dev_priv,
 	/* Check whether the file_priv has already selected one ring. */
 	if ((int)file_priv->bsd_engine < 0)
 		file_priv->bsd_engine =
-			get_random_int() % num_vcs_engines(dev_priv);
+			prandom_u32_max(num_vcs_engines(dev_priv));
 
 	return file_priv->bsd_engine;
 }

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 = prandom_u32() % remaining + low;
+	rover = prandom_u32_max(remaining) + low;
 retry:
 	if (last_used_port != rover) {
 		struct rdma_bind_list *bind_list;