linux-kernel - [PATCH] random: clamp credited irq bits to maximum mixed

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Message-Id: <20220923092204.3818698-1-Jason@zx2c4.com>
Date:   Fri, 23 Sep 2022 11:22:04 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] random: clamp credited irq bits to maximum mixed

Since the most that's mixed into the pool is sizeof(long)*2, don't
credit more than that many bytes of entropy.

Fixes: e3e33fc2ea7f ("random: do not use input pool from hard IRQs")
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/char/random.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 520a385c7dab..593fb3b3cf74 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1004,7 +1004,7 @@ static void mix_interrupt_randomness(struct work_struct *work)
 	local_irq_enable();

 	mix_pool_bytes(pool, sizeof(pool));
-	credit_init_bits(max(1u, (count & U16_MAX) / 64));
+	credit_init_bits(clamp_t(unsigned int, 1, (count & U16_MAX) / 64, sizeof(pool) * 8));

 	memzero_explicit(pool, sizeof(pool));
 }
-- 
2.37.3