[PATCH 5.19 08/33] random: clamp credited irq bits to maximum mixed

Greg Kroah-Hartman
2022-10-13T18:06:22Z

From: Jason A. Donenfeld <Jason@zx2c4.com>

commit e78a802a7b4febf53f2a92842f494b01062d85a8 upstream.

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")
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/random.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -989,7 +989,7 @@ static void mix_interrupt_randomness(str
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, (count & U16_MAX) / 64, 1, sizeof(pool) * 8));

memzero_explicit(pool, sizeof(pool));
}