This is a note to let you know that I've just added the patch titled
random: do not split fast init input in add_hwgenerator_randomness()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random-do-not-split-fast-init-input-in-add_hwgenerator_randomness.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Jun 17 08:58:56 AM CEST 2022
From: Jan Varho <jan.varho@xxxxxxxxx>
Date: Mon, 4 Apr 2022 19:42:30 +0300
Subject: random: do not split fast init input in add_hwgenerator_randomness()
From: Jan Varho <jan.varho@xxxxxxxxx>
commit 527a9867af29ff89f278d037db704e0ed50fb666 upstream.
add_hwgenerator_randomness() tries to only use the required amount of input
for fast init, but credits all the entropy, rather than a fraction of
it. Since it's hard to determine how much entropy is left over out of a
non-unformly random sample, either give it all to fast init or credit
it, but don't attempt to do both. In the process, we can clean up the
injection code to no longer need to return a value.
Signed-off-by: Jan Varho <jan.varho@xxxxxxxxx>
[Jason: expanded commit message]
Fixes: 73c7733f122e ("random: do not throw away excess input to crng_fast_load")
Cc: stable@xxxxxxxxxxxxxxx # 5.17+, requires af704c856e88
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/random.c | 23 ++++++-----------------
1 file changed, 6 insertions(+), 17 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -437,11 +437,8 @@ static void crng_make_state(u32 chacha_s
* This shouldn't be set by functions like add_device_randomness(),
* where we can't trust the buffer passed to it is guaranteed to be
* unpredictable (so it might not have any entropy at all).
- *
- * Returns the number of bytes processed from input, which is bounded
- * by CRNG_INIT_CNT_THRESH if account is true.
*/
-static size_t crng_pre_init_inject(const void *input, size_t len, bool account)
+static void crng_pre_init_inject(const void *input, size_t len, bool account)
{
static int crng_init_cnt = 0;
struct blake2s_state hash;
@@ -452,18 +449,15 @@ static size_t crng_pre_init_inject(const
spin_lock_irqsave(&base_crng.lock, flags);
if (crng_init != 0) {
spin_unlock_irqrestore(&base_crng.lock, flags);
- return 0;
+ return;
}
- if (account)
- len = min_t(size_t, len, CRNG_INIT_CNT_THRESH - crng_init_cnt);
-
blake2s_update(&hash, base_crng.key, sizeof(base_crng.key));
blake2s_update(&hash, input, len);
blake2s_final(&hash, base_crng.key);
if (account) {
- crng_init_cnt += len;
+ crng_init_cnt += min_t(size_t, len, CRNG_INIT_CNT_THRESH - crng_init_cnt);
if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
++base_crng.generation;
crng_init = 1;
@@ -474,8 +468,6 @@ static size_t crng_pre_init_inject(const
if (crng_init == 1)
pr_notice("fast init done\n");
-
- return len;
}
static void _get_random_bytes(void *buf, size_t nbytes)
@@ -1133,12 +1125,9 @@ void add_hwgenerator_randomness(const vo
size_t entropy)
{
if (unlikely(crng_init == 0 && entropy < POOL_MIN_BITS)) {
- size_t ret = crng_pre_init_inject(buffer, count, true);
- mix_pool_bytes(buffer, ret);
- count -= ret;
- buffer += ret;
- if (!count || crng_init == 0)
- return;
+ crng_pre_init_inject(buffer, count, true);
+ mix_pool_bytes(buffer, count);
+ return;
}
/*
Patches currently in stable-queue which might be from jan.varho@xxxxxxxxx are
queue-4.19/random-do-not-split-fast-init-input-in-add_hwgenerator_randomness.patch
