Re: [PATCH v3 4/5] treewide: use get_random_bytes when possible

["Jason A. Donenfeld" <Jason@zx2c4.com>]

On 10/6/22, Bagas Sanjaya <bagasdotme@gmail.com> wrote:
> On 10/6/22 23:53, Jason A. Donenfeld wrote:
>> The prandom_bytes() function has been a deprecated inline wrapper around
>> get_random_bytes() for several releases now, and compiles down to the
>> exact same code. Replace the deprecated wrapper with a direct call to
>> the real function.
>>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
>> ---
>>  arch/powerpc/crypto/crc-vpmsum_test.c       |  2 +-
>>  block/blk-crypto-fallback.c                 |  2 +-
>>  crypto/async_tx/raid6test.c                 |  2 +-
>>  drivers/dma/dmatest.c                       |  2 +-
>>  drivers/mtd/nand/raw/nandsim.c              |  2 +-
>>  drivers/mtd/tests/mtd_nandecctest.c         |  2 +-
>>  drivers/mtd/tests/speedtest.c               |  2 +-
>>  drivers/mtd/tests/stresstest.c              |  2 +-
>>  drivers/net/ethernet/broadcom/bnxt/bnxt.c   |  2 +-
>>  drivers/net/ethernet/rocker/rocker_main.c   |  2 +-
>>  drivers/net/wireguard/selftest/allowedips.c | 12 ++++++------
>>  fs/ubifs/debug.c                            |  2 +-
>>  kernel/kcsan/selftest.c                     |  2 +-
>>  lib/random32.c                              |  2 +-
>>  lib/test_objagg.c                           |  2 +-
>>  lib/uuid.c                                  |  2 +-
>>  net/ipv4/route.c                            |  2 +-
>>  net/mac80211/rc80211_minstrel_ht.c          |  2 +-
>>  net/sched/sch_pie.c                         |  2 +-
>>  19 files changed, 24 insertions(+), 24 deletions(-)
>>
>> diff --git a/arch/powerpc/crypto/crc-vpmsum_test.c
>> b/arch/powerpc/crypto/crc-vpmsum_test.c
>> index c1c1ef9457fb..273c527868db 100644
>> --- a/arch/powerpc/crypto/crc-vpmsum_test.c
>> +++ b/arch/powerpc/crypto/crc-vpmsum_test.c
>> @@ -82,7 +82,7 @@ static int __init crc_test_init(void)
>>
>>  			if (len <= offset)
>>  				continue;
>> -			prandom_bytes(data, len);
>> +			get_random_bytes(data, len);
>>  			len -= offset;
>>
>>  			crypto_shash_update(crct10dif_shash, data+offset, len);
>> diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
>> index 621abd1b0e4d..ad9844c5b40c 100644
>> --- a/block/blk-crypto-fallback.c
>> +++ b/block/blk-crypto-fallback.c
>> @@ -539,7 +539,7 @@ static int blk_crypto_fallback_init(void)
>>  	if (blk_crypto_fallback_inited)
>>  		return 0;
>>
>> -	prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);
>> +	get_random_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);
>>
>>  	err = bioset_init(&crypto_bio_split, 64, 0, 0);
>>  	if (err)
>> diff --git a/crypto/async_tx/raid6test.c b/crypto/async_tx/raid6test.c
>> index c9d218e53bcb..f74505f2baf0 100644
>> --- a/crypto/async_tx/raid6test.c
>> +++ b/crypto/async_tx/raid6test.c
>> @@ -37,7 +37,7 @@ static void makedata(int disks)
>>  	int i;
>>
>>  	for (i = 0; i < disks; i++) {
>> -		prandom_bytes(page_address(data[i]), PAGE_SIZE);
>> +		get_random_bytes(page_address(data[i]), PAGE_SIZE);
>>  		dataptrs[i] = data[i];
>>  		dataoffs[i] = 0;
>>  	}
>> diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
>> index 9fe2ae794316..ffe621695e47 100644
>> --- a/drivers/dma/dmatest.c
>> +++ b/drivers/dma/dmatest.c
>> @@ -312,7 +312,7 @@ static unsigned long dmatest_random(void)
>>  {
>>  	unsigned long buf;
>>
>> -	prandom_bytes(&buf, sizeof(buf));
>> +	get_random_bytes(&buf, sizeof(buf));
>>  	return buf;
>>  }
>>
>> diff --git a/drivers/mtd/nand/raw/nandsim.c
>> b/drivers/mtd/nand/raw/nandsim.c
>> index 4bdaf4aa7007..c941a5a41ea6 100644
>> --- a/drivers/mtd/nand/raw/nandsim.c
>> +++ b/drivers/mtd/nand/raw/nandsim.c
>> @@ -1393,7 +1393,7 @@ static int ns_do_read_error(struct nandsim *ns, int
>> num)
>>  	unsigned int page_no = ns->regs.row;
>>
>>  	if (ns_read_error(page_no)) {
>> -		prandom_bytes(ns->buf.byte, num);
>> +		get_random_bytes(ns->buf.byte, num);
>>  		NS_WARN("simulating read error in page %u\n", page_no);
>>  		return 1;
>>  	}
>> diff --git a/drivers/mtd/tests/mtd_nandecctest.c
>> b/drivers/mtd/tests/mtd_nandecctest.c
>> index 1c7201b0f372..440988562cfd 100644
>> --- a/drivers/mtd/tests/mtd_nandecctest.c
>> +++ b/drivers/mtd/tests/mtd_nandecctest.c
>> @@ -266,7 +266,7 @@ static int nand_ecc_test_run(const size_t size)
>>  		goto error;
>>  	}
>>
>> -	prandom_bytes(correct_data, size);
>> +	get_random_bytes(correct_data, size);
>>  	ecc_sw_hamming_calculate(correct_data, size, correct_ecc, sm_order);
>>  	for (i = 0; i < ARRAY_SIZE(nand_ecc_test); i++) {
>>  		nand_ecc_test[i].prepare(error_data, error_ecc,
>> diff --git a/drivers/mtd/tests/speedtest.c
>> b/drivers/mtd/tests/speedtest.c
>> index c9ec7086bfa1..075bce32caa5 100644
>> --- a/drivers/mtd/tests/speedtest.c
>> +++ b/drivers/mtd/tests/speedtest.c
>> @@ -223,7 +223,7 @@ static int __init mtd_speedtest_init(void)
>>  	if (!iobuf)
>>  		goto out;
>>
>> -	prandom_bytes(iobuf, mtd->erasesize);
>> +	get_random_bytes(iobuf, mtd->erasesize);
>>
>>  	bbt = kzalloc(ebcnt, GFP_KERNEL);
>>  	if (!bbt)
>> diff --git a/drivers/mtd/tests/stresstest.c
>> b/drivers/mtd/tests/stresstest.c
>> index d2faaca7f19d..75b6ddc5dc4d 100644
>> --- a/drivers/mtd/tests/stresstest.c
>> +++ b/drivers/mtd/tests/stresstest.c
>> @@ -183,7 +183,7 @@ static int __init mtd_stresstest_init(void)
>>  		goto out;
>>  	for (i = 0; i < ebcnt; i++)
>>  		offsets[i] = mtd->erasesize;
>> -	prandom_bytes(writebuf, bufsize);
>> +	get_random_bytes(writebuf, bufsize);
>>
>>  	bbt = kzalloc(ebcnt, GFP_KERNEL);
>>  	if (!bbt)
>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> index 96da0ba3d507..354953df46a1 100644
>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> @@ -3874,7 +3874,7 @@ static void bnxt_init_vnics(struct bnxt *bp)
>>
>>  		if (bp->vnic_info[i].rss_hash_key) {
>>  			if (i == 0)
>> -				prandom_bytes(vnic->rss_hash_key,
>> +				get_random_bytes(vnic->rss_hash_key,
>>  					      HW_HASH_KEY_SIZE);
>>  			else
>>  				memcpy(vnic->rss_hash_key,
>> diff --git a/drivers/net/ethernet/rocker/rocker_main.c
>> b/drivers/net/ethernet/rocker/rocker_main.c
>> index 8c3bbafabb07..cd4488efe0a4 100644
>> --- a/drivers/net/ethernet/rocker/rocker_main.c
>> +++ b/drivers/net/ethernet/rocker/rocker_main.c
>> @@ -224,7 +224,7 @@ static int rocker_dma_test_offset(const struct rocker
>> *rocker,
>>  	if (err)
>>  		goto unmap;
>>
>> -	prandom_bytes(buf, ROCKER_TEST_DMA_BUF_SIZE);
>> +	get_random_bytes(buf, ROCKER_TEST_DMA_BUF_SIZE);
>>  	for (i = 0; i < ROCKER_TEST_DMA_BUF_SIZE; i++)
>>  		expect[i] = ~buf[i];
>>  	err = rocker_dma_test_one(rocker, wait, ROCKER_TEST_DMA_CTRL_INVERT,
>> diff --git a/drivers/net/wireguard/selftest/allowedips.c
>> b/drivers/net/wireguard/selftest/allowedips.c
>> index dd897c0740a2..19eac00b2381 100644
>> --- a/drivers/net/wireguard/selftest/allowedips.c
>> +++ b/drivers/net/wireguard/selftest/allowedips.c
>> @@ -284,7 +284,7 @@ static __init bool randomized_test(void)
>>  	mutex_lock(&mutex);
>>
>>  	for (i = 0; i < NUM_RAND_ROUTES; ++i) {
>> -		prandom_bytes(ip, 4);
>> +		get_random_bytes(ip, 4);
>>  		cidr = prandom_u32_max(32) + 1;
>>  		peer = peers[prandom_u32_max(NUM_PEERS)];
>>  		if (wg_allowedips_insert_v4(&t, (struct in_addr *)ip, cidr,
>> @@ -299,7 +299,7 @@ static __init bool randomized_test(void)
>>  		}
>>  		for (j = 0; j < NUM_MUTATED_ROUTES; ++j) {
>>  			memcpy(mutated, ip, 4);
>> -			prandom_bytes(mutate_mask, 4);
>> +			get_random_bytes(mutate_mask, 4);
>>  			mutate_amount = prandom_u32_max(32);
>>  			for (k = 0; k < mutate_amount / 8; ++k)
>>  				mutate_mask[k] = 0xff;
>> @@ -328,7 +328,7 @@ static __init bool randomized_test(void)
>>  	}
>>
>>  	for (i = 0; i < NUM_RAND_ROUTES; ++i) {
>> -		prandom_bytes(ip, 16);
>> +		get_random_bytes(ip, 16);
>>  		cidr = prandom_u32_max(128) + 1;
>>  		peer = peers[prandom_u32_max(NUM_PEERS)];
>>  		if (wg_allowedips_insert_v6(&t, (struct in6_addr *)ip, cidr,
>> @@ -343,7 +343,7 @@ static __init bool randomized_test(void)
>>  		}
>>  		for (j = 0; j < NUM_MUTATED_ROUTES; ++j) {
>>  			memcpy(mutated, ip, 16);
>> -			prandom_bytes(mutate_mask, 16);
>> +			get_random_bytes(mutate_mask, 16);
>>  			mutate_amount = prandom_u32_max(128);
>>  			for (k = 0; k < mutate_amount / 8; ++k)
>>  				mutate_mask[k] = 0xff;
>> @@ -381,13 +381,13 @@ static __init bool randomized_test(void)
>>
>>  	for (j = 0;; ++j) {
>>  		for (i = 0; i < NUM_QUERIES; ++i) {
>> -			prandom_bytes(ip, 4);
>> +			get_random_bytes(ip, 4);
>>  			if (lookup(t.root4, 32, ip) != horrible_allowedips_lookup_v4(&h,
>> (struct in_addr *)ip)) {
>>  				horrible_allowedips_lookup_v4(&h, (struct in_addr *)ip);
>>  				pr_err("allowedips random v4 self-test: FAIL\n");
>>  				goto free;
>>  			}
>> -			prandom_bytes(ip, 16);
>> +			get_random_bytes(ip, 16);
>>  			if (lookup(t.root6, 128, ip) != horrible_allowedips_lookup_v6(&h,
>> (struct in6_addr *)ip)) {
>>  				pr_err("allowedips random v6 self-test: FAIL\n");
>>  				goto free;
>> diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
>> index f4d3b568aa64..3f128b9fdfbb 100644
>> --- a/fs/ubifs/debug.c
>> +++ b/fs/ubifs/debug.c
>> @@ -2581,7 +2581,7 @@ static int corrupt_data(const struct ubifs_info *c,
>> const void *buf,
>>  	if (ffs)
>>  		memset(p + from, 0xFF, to - from);
>>  	else
>> -		prandom_bytes(p + from, to - from);
>> +		get_random_bytes(p + from, to - from);
>>
>>  	return to;
>>  }
>> diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c
>> index 58b94deae5c0..00cdf8fa5693 100644
>> --- a/kernel/kcsan/selftest.c
>> +++ b/kernel/kcsan/selftest.c
>> @@ -46,7 +46,7 @@ static bool __init test_encode_decode(void)
>>  		unsigned long addr;
>>  		size_t verif_size;
>>
>> -		prandom_bytes(&addr, sizeof(addr));
>> +		get_random_bytes(&addr, sizeof(addr));
>>  		if (addr < PAGE_SIZE)
>>  			addr = PAGE_SIZE;
>>
>> diff --git a/lib/random32.c b/lib/random32.c
>> index d4f19e1a69d4..32060b852668 100644
>> --- a/lib/random32.c
>> +++ b/lib/random32.c
>> @@ -69,7 +69,7 @@ EXPORT_SYMBOL(prandom_u32_state);
>>   *	@bytes: the requested number of bytes
>>   *
>>   *	This is used for pseudo-randomness with no outside seeding.
>> - *	For more random results, use prandom_bytes().
>> + *	For more random results, use get_random_bytes().
>>   */
>>  void prandom_bytes_state(struct rnd_state *state, void *buf, size_t
>> bytes)
>>  {
>> diff --git a/lib/test_objagg.c b/lib/test_objagg.c
>> index da137939a410..c0c957c50635 100644
>> --- a/lib/test_objagg.c
>> +++ b/lib/test_objagg.c
>> @@ -157,7 +157,7 @@ static int test_nodelta_obj_get(struct world *world,
>> struct objagg *objagg,
>>  	int err;
>>
>>  	if (should_create_root)
>> -		prandom_bytes(world->next_root_buf,
>> +		get_random_bytes(world->next_root_buf,
>>  			      sizeof(world->next_root_buf));
>>
>>  	objagg_obj = world_obj_get(world, objagg, key_id);
>> diff --git a/lib/uuid.c b/lib/uuid.c
>> index 562d53977cab..e309b4c5be3d 100644
>> --- a/lib/uuid.c
>> +++ b/lib/uuid.c
>> @@ -52,7 +52,7 @@ EXPORT_SYMBOL(generate_random_guid);
>>
>>  static void __uuid_gen_common(__u8 b[16])
>>  {
>> -	prandom_bytes(b, 16);
>> +	get_random_bytes(b, 16);
>>  	/* reversion 0b10 */
>>  	b[8] = (b[8] & 0x3F) | 0x80;
>>  }
>> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
>> index 1a37a07c7163..cd1fa9f70f1a 100644
>> --- a/net/ipv4/route.c
>> +++ b/net/ipv4/route.c
>> @@ -3719,7 +3719,7 @@ int __init ip_rt_init(void)
>>
>>  	ip_idents = idents_hash;
>>
>> -	prandom_bytes(ip_idents, (ip_idents_mask + 1) * sizeof(*ip_idents));
>> +	get_random_bytes(ip_idents, (ip_idents_mask + 1) * sizeof(*ip_idents));
>>
>>  	ip_tstamps = idents_hash + (ip_idents_mask + 1) * sizeof(*ip_idents);
>>
>> diff --git a/net/mac80211/rc80211_minstrel_ht.c
>> b/net/mac80211/rc80211_minstrel_ht.c
>> index 5f27e6746762..39fb4e2d141a 100644
>> --- a/net/mac80211/rc80211_minstrel_ht.c
>> +++ b/net/mac80211/rc80211_minstrel_ht.c
>> @@ -2033,7 +2033,7 @@ static void __init init_sample_table(void)
>>
>>  	memset(sample_table, 0xff, sizeof(sample_table));
>>  	for (col = 0; col < SAMPLE_COLUMNS; col++) {
>> -		prandom_bytes(rnd, sizeof(rnd));
>> +		get_random_bytes(rnd, sizeof(rnd));
>>  		for (i = 0; i < MCS_GROUP_RATES; i++) {
>>  			new_idx = (i + rnd[i]) % MCS_GROUP_RATES;
>>  			while (sample_table[col][new_idx] != 0xff)
>> diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
>> index 5a457ff61acd..66b2b23e8cd1 100644
>> --- a/net/sched/sch_pie.c
>> +++ b/net/sched/sch_pie.c
>> @@ -72,7 +72,7 @@ bool pie_drop_early(struct Qdisc *sch, struct pie_params
>> *params,
>>  	if (vars->accu_prob >= (MAX_PROB / 2) * 17)
>>  		return true;
>>
>> -	prandom_bytes(&rnd, 8);
>> +	get_random_bytes(&rnd, 8);
>>  	if ((rnd >> BITS_PER_BYTE) < local_prob) {
>>  		vars->accu_prob = 0;
>>  		return true;
>
> Are there cases where calling get_random_bytes() is not possible?

Yes, but that has absolutely zero bearing whatsoever on this patch
4/5, considering the code this generates is identical. If you have
serious questions about contexts the rng can operate in, please start
another thread, where you can flesh out that inquiry a but more.

Jason