linux-kernel - [PATCH 2/6] hw_random: read() callback must be called for size of 32 or more bytes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220124202951.28579-2-linux@dominikbrodowski.net>
Date:   Mon, 24 Jan 2022 21:29:47 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        "Jason A . Donenfeld" <Jason@...c4.com>
Subject: [PATCH 2/6] hw_random: read() callback must be called for size of 32 or more bytes

According to <linux/hw_random.h>, the @max parameter of the ->read
callback "is a multiple of 4 and >= 32 bytes". That promise was not
kept by add_early_randomness(), which only asked for 16 bytes. As
rng_buffer_size() is at least 32, we can simply ask for 32 bytes.

Cc: Matt Mackall <mpm@...enic.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
---
 drivers/char/hw_random/core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index e860e044b19e..c2d260b5dd92 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -64,10 +64,9 @@ static size_t rng_buffer_size(void)
 static void add_early_randomness(struct hwrng *rng)
 {
 	int bytes_read;
-	size_t size = min_t(size_t, 16, rng_buffer_size());
 
 	mutex_lock(&reading_mutex);
-	bytes_read = rng_get_data(rng, rng_buffer, size, 0);
+	bytes_read = rng_get_data(rng, rng_buffer, 32, 0);
 	mutex_unlock(&reading_mutex);
 	if (bytes_read > 0)
 		add_device_randomness(rng_buffer, bytes_read);
-- 
2.34.1