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    Subject[PATCH 4.9 031/159] random: clamp credited irq bits to maximum mixed
    Date
    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
    @@ -977,7 +977,7 @@ 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));
    }

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